Tektronix 2651A Reference manual

Model 2651A High Power
System SourceMeter Instrument

Reference Manual

2651A-901-01 Rev. C October 2021

tek.com/keithley

*P2651A-901-01C*

2651A-901-01C

High Power System SourceMeter® Instrument

Reference Manual

Model 2651A

© 2021, Keithley Instruments, LLC

Cleveland, Ohio, U.S.A.

All rights reserved.

Any unauthorized reproduction, photocopy, or use of the information herein, in whole or in part,

without the prior written approval of Keithley Instruments, LLC, is strictly prohibited.

These are the original instructions in English.

TSPTM, TSP-LinkTM, and TSP-NetTM are trademarks of Keithley Instruments, LLC. All Keithley

Instruments product names are trademarks or registered trademarks of Keithley Instruments, LLC.

Other brand names are trademarks or registered trademarks of their respective holders.

The Lua 5.0 software and associated documentation files are copyright © 1994 - 2015, Lua.org,

PUC-Rio. You can access terms of license for the Lua software and associated documentation at

the Lua licensing site (https://www.lua.org/license.html).

Microsoft, Visual C++, Excel, and Windows are either registered trademarks or trademarks of

Microsoft Corporation in the United States and/or other countries.

Document number: 2651A-901-01 Rev. C October 2021

Safety precautions

The following safety precautions should be observed before using this product and any associated instrumentation. Although
some instruments and accessories would normally be used with nonhazardous voltages, there are situations where hazardous
conditions may be present.

This product is intended for use by personnel who recognize shock hazards and are familiar with the safety precautions required
to avoid possible injury. Read and follow all installation, operation, and maintenance information carefully before using the
product. Refer to the user documentation for complete product specifications.

If the product is used in a manner not specified, the protection provided by the product warranty may be impaired.
The types of product users are:

Responsible body is the individual or group responsible for the use and maintenance of equipment, for ensuring that the
equipment is operated within its specifications and operating limits, and for ensuring that operators are adequately trained.

Operators use the product for its intended function. They must be trained in electrical safety procedures and proper use of the
instrument. They must be protected from electric shock and contact with hazardous live circuits.

Maintenance personnel perform routine procedures on the product to keep it operating properly, for example, setting the line
voltage or replacing consumable materials. Maintenance procedures are described in the user documentation. The procedures
explicitly state if the operator may perform them. Otherwise, they should be performed only by service personnel.

Service personnel are trained to work on live circuits, perform safe installations, and repair products. Only properly trained
service personnel may perform installation and service procedures.

Keithley products are designed for use with electrical signals that are measurement, control, and data I/O connections, with low
transient overvoltages, and must not be directly connected to mains voltage or to voltage sources with high transient
overvoltages. Measurement Category II (as referenced in IEC 60664) connections require protection for high transient
overvoltages often associated with local AC mains connections. Certain Keithley measuring instruments may be connected to
mains. These instruments will be marked as category II or higher.

Unless explicitly allowed in the specifications, operating manual, and instrument labels, do not connect any instrument to mains.
Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector jacks or test

fixtures. The American National Standards Institute (ANSI) states that a shock hazard exists when voltage levels greater than
30 V RMS, 42.4 V peak, or 60 VDC are present. A good safety practice is to expect that hazardous voltage is present in any
unknown circuit before measuring.

Operators of this product must be protected from electric shock at all times. The responsible body must ensure that operators
are prevented access and/or insulated from every connection point. In some cases, connections must be exposed to potential
human contact. Product operators in these circumstances must be trained to protect themselves from the risk of electric shock. If
the circuit is capable of operating at or above 1000 V, no conductive part of the circuit may be exposed.

Do not connect switching cards directly to unlimited power circuits. They are intended to be used with impedance-limited
sources. NEVER connect switching cards directly to AC mains. When connecting sources to switching cards, install protective
devices to limit fault current and voltage to the card.

Before operating an instrument, ensure that the line cord is connected to a properly-grounded power receptacle. Inspect the
connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.

When installing equipment where access to the main power cord is restricted, such as rack mounting, a separate main input
power disconnect device must be provided in close proximity to the equipment and within easy reach of the operator.

For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the circuit under
test. ALWAYS remove power from the entire test system and discharge any capacitors before: connecting or disconnecting
cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers.

Do not touch any object that could provide a current path to the common side of the circuit under test or power line (earth)
ground. Always make measurements with dry hands while standing on a dry, insulated surface capable of withstanding the
voltage being measured.

For safety, instruments and accessories must be used in accordance with the operating instructions. If the instruments or
accessories are used in a manner not specified in the operating instructions, the protection provided by the equipment may be
impaired.

Do not exceed the maximum signal levels of the instruments and accessories. Maximum signal levels are defined in the
specifications and operating information and shown on the instrument panels, test fixture panels, and switching cards.

When fuses are used in a product, replace with the same type and rating for continued protection against fire hazard.
Chassis connections must only be used as shield connections for measuring circuits, NOT as protective earth (safety ground)

connections.
If you are using a test fixture, keep the lid closed while power is applied to the device under test. Safe operation requires the use

of a lid interlock.

If a screw is present, connect it to protective earth (safety ground) using the wire recommended in the user documentation.

The symbol on an instrument means caution, risk of hazard. The user must refer to the operating instructions located in the
user documentation in all cases where the symbol is marked on the instrument.

The symbol on an instrument means warning, risk of electric shock. Use standard safety precautions to avoid personal
contact with these voltages.

The symbol on an instrument shows that the surface may be hot. Avoid personal contact to prevent burns.

The symbol indicates a connection terminal to the equipment frame.

If this symbol is on a product, it indicates that mercury is present in the display lamp. Please note that the lamp must be
properly disposed of according to federal, state, and local laws.

The WARNING heading in the user documentation explains hazards that might result in personal injury or death. Always read
the associated information very carefully before performing the indicated procedure.

The CAUTION heading in the user documentation explains hazards that could damage the instrument. Such damage may
invalidate the warranty.

The CAUTION heading with the symbol in the user documentation explains hazards that could result in moderate or minor
injury or damage the instrument. Always read the associated information very carefully before performing the indicated
procedure. Damage to the instrument may invalidate the warranty.

Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and all test cables.
To maintain protection from electric shock and fire, replacement components in mains circuits — including the power

transformer, test leads, and input jacks — must be purchased from Keithley. Standard fuses with applicable national safety
approvals may be used if the rating and type are the same. The detachable mains power cord provided with the instrument may
only be replaced with a similarly rated power cord. Other components that are not safety-related may be purchased from other
suppliers as long as they are equivalent to the original component (note that selected parts should be purchased only through
Keithley to maintain accuracy and functionality of the product). If you are unsure about the applicability of a replacement
component, call a Keithley office for information.

Unless otherwise noted in product-specific literature, Keithley instruments are designed to operate indoors only, in the following
environment: Altitude at or below 2,000 m (6,562 ft); temperature 0 °C to 50 °C (32 °F to 122 °F); and pollution degree 1 or 2.

To clean an instrument, use a cloth dampened with deionized water or mild, water-based cleaner. Clean the exterior of the
instrument only. Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument. Products that
consist of a circuit board with no case or chassis (e.g., a data acquisition board for installation into a computer) should never
require cleaning if handled according to instructions. If the board becomes contaminated and operation is affected, the board
should be returned to the factory for proper cleaning/servicing.

Safety precaution revision as of June 2017.

Introduction .............................................................................................................. 1-1

Welcome .............................................................................................................................. 1-1

Extended warranty ............................................................................................................... 1-1

Contact information .............................................................................................................. 1-1

Customer documentation ..................................................................................................... 1-2

Organization of manual sections ............................................................................................... 1-2

Capabilities and features...................................................................................................... 1-3

Model-specific capabilities ................................................................................................... 1-4

General information .............................................................................................................. 1-4

Displaying the serial number ..................................................................................................... 1-4

General operation .................................................................................................... 2-1

General ratings ..................................................................................................................... 2-1

Controls, indicators, and connectors .................................................................................... 2-2

Front panel ................................................................................................................................ 2-2

Rear panel................................................................................................................................. 2-6

Cooling vents ....................................................................................................................... 2-8

Starting up your instrument .................................................................................................. 2-9

Procedure.................................................................................................................................. 2-9

Placing the Model 2651A in standby ....................................................................................... 2-10

Warmup period ........................................................................................................................ 2-10

Line frequency configuration ................................................................................................... 2-10

Fuse replacement ................................................................................................................... 2-11

System information ............................................................................................................ 2-11

Menu overview ................................................................................................................... 2-11

Menu navigation ...................................................................................................................... 2-11

Menu trees .............................................................................................................................. 2-13

Setting values .......................................................................................................................... 2-16

Beeper ................................................................................................................................ 2-18

Display mode ..................................................................................................................... 2-19

Basic operation .................................................................................................................. 2-19

Operation overview ................................................................................................................. 2-19

Operation considerations for the ADC ..................................................................................... 2-25

Basic source-measure procedure ........................................................................................... 2-27

Triggering in local mode .......................................................................................................... 2-30

Configuring trigger attributes in local mode ............................................................................. 2-31

Configuring for measure-only tests using the MODE key ........................................................ 2-32

Voltmeter and ammeter measurements .................................................................................. 2-33

Ohms measurements ................................................................ .............................................. 2-34

Power measurements ............................................................................................................. 2-37

Contact check measurements ................................................................................................. 2-40

Saved setups .......................................................................................................................... 2-42

DUT test connections ......................................................................................................... 2-45

Input/output connectors ........................................................................................................... 2-45

2-wire local sensing connections ............................................................................................. 2-47

Table of contents

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

4-wire remote sensing connections ......................................................................................... 2-48

Contact check connections ..................................................................................................... 2-49

Multiple SMU connections ....................................................................................................... 2-50

Combining SMU outputs ......................................................................................................... 2-51

Guarding and shielding ........................................................................................................... 2-57

Test fixture .............................................................................................................................. 2-62

Floating a SMU ....................................................................................................................... 2-63

DUT connection settings .................................................................................................... 2-64

Sense mode selection ................................................................ ............................................. 2-64

Output-off states ...................................................................................................................... 2-65

USB storage overview ........................................................................................................ 2-69

Connecting the USB flash drive .............................................................................................. 2-70

File system navigation ............................................................................................................. 2-70

Displayed error and status messages ................................................................................ 2-71

Range ................................................................................................................................. 2-71

Available ranges ...................................................................................................................... 2-72

Maximum source values and readings ................................ ................................ .................... 2-72

Measure autodelay .................................................................................................................. 2-73

Ranging limitations .................................................................................................................. 2-73

Manual ranging ....................................................................................................................... 2-73

Autoranging ............................................................................................................................. 2-74

Low range limits ...................................................................................................................... 2-74

Range considerations ............................................................................................................. 2-75

Range programming ............................................................................................................... 2-76

Digits .................................................................................................................................. 2-77

Setting display resolution from the front panel ........................................................................ 2-77

Setting display resolution from a remote interface .................................................................. 2-77

Speed ................................................................................................................................. 2-78

Setting the speed from the front panel .................................................................................... 2-78

Setting the speed using the remote interface .......................................................................... 2-79

Remote communications interfaces ................................................................................... 2-80

Supported remote interfaces ................................................................................................... 2-80

Output queue .......................................................................................................................... 2-81

LAN communications .............................................................................................................. 2-81

GPIB operation ........................................................................................................................ 2-83

General bus commands .......................................................................................................... 2-86

Front-panel GPIB operation .................................................................................................... 2-88

RS-232 interface operation ..................................................................................................... 2-90

Functions and features ............................................................................................ 3-1

Relative offset ...................................................................................................................... 3-1

Enabling and disabling relative offset from the front panel ........................................................ 3-1

Defining a relative offset value from the front panel .................................................................. 3-2

Relative offset commands ......................................................................................................... 3-2

Filters.................................................................................................................................... 3-3

Filter types................................................................................................................................. 3-3

Response time .......................................................................................................................... 3-4

Enabling the filter from the front panel ...................................................................................... 3-4

Configuring the filter from the front panel .................................................................................. 3-5

Setting the filter using a remote interface .................................................................................. 3-5

Reading buffers .................................................................................................................... 3-6

Front-panel reading buffer control ............................................................................................. 3-6

Remote reading buffer programming ...................................................................................... 3-11

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

Sweep operation ................................................................................................................ 3-21

Sweep characteristics ............................................................................................................. 3-23

Configuring and running sweeps ............................................................................................. 3-31

Sweeping using factory scripts ................................................................................................ 3-33

Sweep programming examples ............................................................................................... 3-34

Triggering ........................................................................................................................... 3-36

Remote triggering overview..................................................................................................... 3-36

Using the remote trigger model ............................................................................................... 3-38

SMU event detectors ............................................................................................................... 3-42

Using trigger events to start actions on trigger objects ............................................................ 3-44

Digital I/O port and TSP-Link synchronization lines ................................................................ 3-45

Timers ..................................................................................................................................... 3-48

Event blenders ........................................................................................................................ 3-57

LAN triggering overview .......................................................................................................... 3-58

Command interface triggering ................................................................................................. 3-60

Manual triggering .................................................................................................................... 3-60

Interactive triggering ................................................................................................................ 3-61

Hardware trigger modes .......................................................................................................... 3-65

Understanding synchronous triggering modes ........................................................................ 3-69

High-capacitance mode ..................................................................................................... 3-73

Understanding high-capacitance mode ................................ ................................ ................... 3-73

Enabling high-capacitance mode ............................................................................................ 3-76

Display operations .............................................................................................................. 3-79

Display functions and attributes .............................................................................................. 3-79

Display features ...................................................................................................................... 3-79

Display messages ................................................................................................................... 3-81

Input prompting ....................................................................................................................... 3-85

Indicators................................................................................................................................. 3-87

Local lockout ................................ ................................ ........................................................... 3-88

Load test menu ....................................................................................................................... 3-88

Running a test from the front panel ......................................................................................... 3-90

Key-press codes ..................................................................................................................... 3-90

Digital I/O ........................................................................................................................... 3-92

Port configuration .................................................................................................................... 3-92

Digital I/O configuration ........................................................................................................... 3-94

Controlling digital I/O lines....................................................................................................... 3-94

Using output enable ................................................................................................................ 3-96

Interlock................................................................................................................................... 3-98

TSP-Link trigger lines ................................................................ .............................................. 3-98

Theory of operation ................................................................................................. 4-1

Analog-to-digital converter ................................................................................................... 4-1

Source-measure concepts ................................................................................................... 4-2

Limit principles .......................................................................................................................... 4-2

Overheating protection .............................................................................................................. 4-3

Operating boundaries ................................................................................................................ 4-5

Basic circuit configurations ...................................................................................................... 4-20

Guard ...................................................................................................................................... 4-24

Cable considerations ............................................................................................................... 4-26

Measurement settling time considerations ......................................................................... 4-27

Programming example for controlling settling time delay ........................................................ 4-28

Effects of load on current source settling time ................................................................... 4-28

Creating pulses with the Model 2651A SMU ..................................................................... 4-29

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

Pulse rise and fall times .......................................................................................................... 4-29

Pulse width .............................................................................................................................. 4-30

Remote commands .................................................................................................. 5-1

Introduction to TSP operation .............................................................................................. 5-1

Controlling the instrument by sending individual command messages ..................................... 5-1

Queries ..................................................................................................................................... 5-3

Information on scripting and programming ................................................................................ 5-3

About TSP commands ......................................................................................................... 5-4

Beeper control ........................................................................................................................... 5-4

Bit manipulation and logic operations ........................................................................................ 5-4

Data queue................................................................................................................................ 5-5

Digital I/O .................................................................................................................................. 5-5

Display ...................................................................................................................................... 5-6

Error queue ............................................................................................................................... 5-7

Event log ................................................................................................................................... 5-7

File I/O ...................................................................................................................................... 5-7

GPIB ......................................................................................................................................... 5-8

Instrument identification ............................................................................................................ 5-9

LAN and LXI .............................................................................................................................. 5-9

Miscellaneous ......................................................................................................................... 5-10

Parallel script execution .......................................................................................................... 5-11

Queries and response messages ............................................................................................ 5-11

Reading buffer ......................................................................................................................... 5-12

Reset ....................................................................................................................................... 5-12

RS-232 ................................................................ .................................................................... 5-13

Saved setups .......................................................................................................................... 5-13

Scripting .................................................................................................................................. 5-13

SMU ........................................................................................................................................ 5-14

SMU calibration ....................................................................................................................... 5-15

Status model ................................ ................................ ........................................................... 5-16

Time ........................................................................................................................................ 5-17

Triggering ................................................................................................................................ 5-17

TSP-Link ................................................................................................................................. 5-19

TSP-Net .................................................................................................................................. 5-20

Userstrings .............................................................................................................................. 5-20

Factory scripts .................................................................................................................... 5-21

Running a factory script .......................................................................................................... 5-21

Retrieving and modifying a factory script listing ...................................................................... 5-22

KISweep factory script ............................................................................................................ 5-22

KIPulse factory script .............................................................................................................. 5-23

KIHighC factory script ............................................................................................................. 5-24

KIParlib factory script .............................................................................................................. 5-25

KISavebuffer factory script ...................................................................................................... 5-25

Instrument programming ......................................................................................... 6-1

Fundamentals of scripting for TSP ....................................................................................... 6-1

What is a script? ........................................................................................................................ 6-2

Runtime and nonvolatile memory storage of scripts .................................................................. 6-2

What can be included in scripts? ............................................................................................... 6-3

Commands that cannot be used in scripts ................................................................................ 6-3

Manage scripts .......................................................................................................................... 6-3

Working with scripts in nonvolatile memory............................................................................. 6-11

Programming example: Interactive script ................................................................................ 6-13

Fundamentals of programming for TSP ............................................................................. 6-15

What is Lua? ................................ ................................ ........................................................... 6-15

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

Lua basics ............................................................................................................................... 6-15

Standard libraries .................................................................................................................... 6-30

Script with a for loop ................................................................................................................ 6-34

Test Script Builder .............................................................................................................. 6-34

Installing the TSB software...................................................................................................... 6-35

Using Test Script Builder (TSB) .............................................................................................. 6-35

Project navigator ..................................................................................................................... 6-36

Script editor ............................................................................................................................. 6-37

Outline view............................................................................................................................. 6-37

Programming interaction ......................................................................................................... 6-38

Working with TSB Embedded ............................................................................................ 6-39

Send individual instrument commands with TSB Embedded .................................................. 6-40

Password management ..................................................................................................... 6-41

Setting the password from a command or web interface ........................................................ 6-42

Unlocking the remote interface ................................................................................................ 6-43

Resetting the password ........................................................................................................... 6-43

Advanced scripting for TSP ............................................................................................... 6-44

Global variables and the script.user.scripts table .................................................................... 6-44

Create a script using the script.new() command ..................................................................... 6-45

Rename a script ...................................................................................................................... 6-48

Retrieve a user script .............................................................................................................. 6-50

Delete user scripts from the instrument ................................................................................... 6-52

Restore a script to the runtime environment ........................................................................... 6-53

Memory considerations for the runtime environment .............................................................. 6-53

TSP-Link system expansion interface ................................................................................ 6-55

Master and subordinates ......................................................................................................... 6-55

TSP-Link system ..................................................................................................................... 6-56

TSP-Link nodes ....................................................................................................................... 6-56

Connections ................................................................ ............................................................ 6-57

Initialization ............................................................................................................................. 6-57

Resetting the TSP-Link network .............................................................................................. 6-58

Accessing nodes ..................................................................................................................... 6-59

Using the reset() command ..................................................................................................... 6-60

Using the abort command ....................................................................................................... 6-60

Triggering with TSP-Link ......................................................................................................... 6-60

TSP advanced features ........................................................................................................... 6-61

Using groups to manage nodes on TSP-Link network ............................................................ 6-64

Running simultaneous test scripts ........................................................................................... 6-65

Using the data queue for real-time communication ................................................................. 6-67

Copying test scripts across the TSP-Link network .................................................................. 6-67

Removing stale values from the reading buffer cache ............................................................ 6-67

TSP-Net ............................................................................................................................. 6-68

TSP-Net capabilities ................................................................................................................ 6-68

Using TSP-Net with any ethernet-enabled instrument ............................................................ 6-69

TSP-Net compared to TSP-Link to communicate with TSP-enabled devices ......................... 6-71

TSP-Net instrument commands: General device control ........................................................ 6-71

TSP-Net instrument commands: TSP-enabled device control ................................................ 6-71

Example: Using tspnet commands .......................................................................................... 6-72

TSP command reference ......................................................................................... 7-1

TSP command programming notes ..................................................................................... 7-1

Placeholder text ........................................................................................................................ 7-1

Syntax rules .............................................................................................................................. 7-2

Time and date values ................................................................................................................ 7-2

Remote versus local state ......................................................................................................... 7-3

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

Using the TSP command reference ..................................................................................... 7-3

Command name and summary table ........................................................................................ 7-4

Command usage ....................................................................................................................... 7-5

Command details ...................................................................................................................... 7-6

Example section ........................................................................................................................ 7-6

Related commands and information .......................................................................................... 7-7

TSP commands .................................................................................................................... 7-7

beeper.beep() ............................................................................................................................ 7-7

beeper.enable ........................................................................................................................... 7-8

bit.bitand() ................................................................................................................................. 7-8

bit.bitor() .................................................................................................................................... 7-9

bit.bitxor() ................................................................................................................................ 7-10

bit.clear() ................................................................................................................................. 7-11

bit.get() .................................................................................................................................... 7-12

bit.getfield() ............................................................................................................................. 7-13

bit.set() .................................................................................................................................... 7-14

bit.setfield().............................................................................................................................. 7-15

bit.test() ................................................................................................................................... 7-16

bit.toggle() ............................................................................................................................... 7-17

bufferVar.appendmode ........................................................................................................... 7-18

bufferVar.basetimestamp ........................................................................................................ 7-19

bufferVar.cachemode .............................................................................................................. 7-20

bufferVar.capacity ................................................................................................................... 7-21

bufferVar.clear() ...................................................................................................................... 7-22

bufferVar.clearcache() ............................................................................................................. 7-22

bufferVar.collectsourcevalues ................................................................................................. 7-23

bufferVar.collecttimestamps .................................................................................................... 7-24

bufferVar.fillcount .................................................................................................................... 7-25

bufferVar.fillmode .................................................................................................................... 7-26

bufferVar.measurefunctions .................................................................................................... 7-27

bufferVar.measureranges ....................................................................................................... 7-28

bufferVar.n .............................................................................................................................. 7-29

bufferVar.readings ................................................................................................................... 7-30

bufferVar.sourcefunctions ....................................................................................................... 7-31

bufferVar.sourceoutputstates ................................................................................................ .. 7-32

bufferVar.sourceranges ........................................................................................................... 7-33

bufferVar.sourcevalues ........................................................................................................... 7-34

bufferVar.statuses ................................................................................................................... 7-35

bufferVar.timestampresolution ................................................................................................ 7-36

bufferVar.timestamps .............................................................................................................. 7-37

ConfigPulseIMeasureV() ......................................................................................................... 7-38

ConfigPulseIMeasureVSweepLin() ......................................................................................... 7-40

ConfigPulseIMeasureVSweepLog() ........................................................................................ 7-42

ConfigPulseVMeasureI() ......................................................................................................... 7-44

ConfigPulseVMeasureISweepLin() ......................................................................................... 7-47

ConfigPulseVMeasureISweepLog() ........................................................................................ 7-49

dataqueue.add() ...................................................................................................................... 7-51

dataqueue.CAPACITY ............................................................................................................ 7-52

dataqueue.clear() .................................................................................................................... 7-53

dataqueue.count ..................................................................................................................... 7-54

dataqueue.next() ..................................................................................................................... 7-55

delay() ..................................................................................................................................... 7-57

digio.readbit() .......................................................................................................................... 7-58

digio.readport() ........................................................................................................................ 7-59

digio.trigger[N].assert() ............................................................................................................ 7-60

digio.trigger[N].clear() .............................................................................................................. 7-60

digio.trigger[N].EVENT_ID ...................................................................................................... 7-61

digio.trigger[N].mode ................................................................................................ ............... 7-62

digio.trigger[N].overrun ............................................................................................................ 7-63

digio.trigger[N].pulsewidth ....................................................................................................... 7-64

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

digio.trigger[N].release() .......................................................................................................... 7-65

digio.trigger[N].reset() ............................................................................................................. 7-65

digio.trigger[N].stimulus ........................................................................................................... 7-66

digio.trigger[N].wait() ............................................................................................................... 7-68

digio.writebit() .......................................................................................................................... 7-69

digio.writeport() ....................................................................................................................... 7-70

digio.writeprotect ..................................................................................................................... 7-71

display.clear() .......................................................................................................................... 7-71

display.getannunciators() ........................................................................................................ 7-72

display.getcursor() ................................................................................................................... 7-74

display.getlastkey() ................................................................................................................. 7-75

display.gettext() ....................................................................................................................... 7-76

display.inputvalue() ................................................................................................................. 7-78

display.loadmenu.add() ........................................................................................................... 7-79

display.loadmenu.catalog() ..................................................................................................... 7-81

display.loadmenu.delete() ....................................................................................................... 7-82

display.locallockout ................................................................................................................. 7-83

display.menu() ......................................................................................................................... 7-84

display.numpad ....................................................................................................................... 7-85

display.prompt() ...................................................................................................................... 7-85

display.screen ......................................................................................................................... 7-87

display.sendkey() .................................................................................................................... 7-87

display.setcursor() ................................................................................................................... 7-89

display.settext() ....................................................................................................................... 7-90

display.smuX.digits ................................................................................................................. 7-91

display.smuX.limit.func ............................................................................................................ 7-92

display.smuX.measure.func .................................................................................................... 7-93

display.trigger.clear() ............................................................................................................... 7-94

display.trigger.EVENT_ID ....................................................................................................... 7-94

display.trigger.overrun ............................................................................................................. 7-95

display.trigger.wait() ................................................................................................................ 7-95

display.waitkey() ...................................................................................................................... 7-96

errorqueue.clear() ................................................................................................................... 7-98

errorqueue.count ..................................................................................................................... 7-98

errorqueue.next() .................................................................................................................... 7-99

eventlog.all() .......................................................................................................................... 7-100

eventlog.clear() ..................................................................................................................... 7-101

eventlog.count ....................................................................................................................... 7-101

eventlog.enable ..................................................................................................................... 7-102

eventlog.next() ...................................................................................................................... 7-102

eventlog.overwritemethod ..................................................................................................... 7-103

exit() ...................................................................................................................................... 7-104

fileVar:close() ........................................................................................................................ 7-104

fileVar:flush() ......................................................................................................................... 7-105

fileVar:read() ......................................................................................................................... 7-107

fileVar:seek() ......................................................................................................................... 7-108

fileVar:write() ......................................................................................................................... 7-110

format.asciiprecision ............................................................................................................. 7-111

format.byteorder .................................................................................................................... 7-112

format.data ............................................................................................................................ 7-113

fs.chdir() ................................................................................................................................ 7-114

fs.cwd() ................................................................................................................................. 7-115

fs.is_dir() ............................................................................................................................... 7-116

fs.is_file() ............................................................................................................................... 7-117

fs.mkdir() ............................................................................................................................... 7-118

fs.readdir() ............................................................................................................................. 7-119

fs.rmdir() ................................................................................................................................ 7-120

gettimezone() ........................................................................................................................ 7-121

gm_isweep() .......................................................................................................................... 7-122

gm_vsweep() ......................................................................................................................... 7-123

gpib.address .......................................................................................................................... 7-124

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

i_leakage_measure() ............................................................................................................ 7-125

i_leakage_threshold() ............................................................................................................ 7-126

InitiatePulseTest() ................................................................................................................. 7-128

io.close()................................................................................................................................ 7-129

io.flush() ................................................................................................................................ 7-130

io.input() ................................................................................................................................ 7-131

io.open() ................................................................................................................................ 7-132

io.output() .............................................................................................................................. 7-133

io.read() ................................................................................................................................. 7-134

io.type() ................................................................................................................................. 7-135

io.write() ................................................................................................................................ 7-136

lan.applysettings() ................................................................................................................. 7-138

lan.autoconnect ..................................................................................................................... 7-139

lan.config.dns.address[N] ...................................................................................................... 7-140

lan.config.dns.domain ........................................................................................................... 7-141

lan.config.dns.dynamic .......................................................................................................... 7-142

lan.config.dns.hostname ....................................................................................................... 7-143

lan.config.dns.verify .............................................................................................................. 7-144

lan.config.duplex ................................................................................................................... 7-144

lan.config.gateway ................................................................................................................ 7-145

lan.config.ipaddress .............................................................................................................. 7-146

lan.config.method .................................................................................................................. 7-147

lan.config.speed .................................................................................................................... 7-148

lan.config.subnetmask .......................................................................................................... 7-149

lan.linktimeout ....................................................................................................................... 7-149

lan.lxidomain ................................ ................................ ......................................................... 7-150

lan.nagle................................................................................................................................ 7-151

lan.reset() .............................................................................................................................. 7-151

lan.restoredefaults() .............................................................................................................. 7-152

lan.status.dns.address[N] ...................................................................................................... 7-153

lan.status.dns.name .............................................................................................................. 7-154

lan.status.duplex ................................................................................................................... 7-155

lan.status.gateway ................................................................................................................ 7-155

lan.status.ipaddress .............................................................................................................. 7-156

lan.status.macaddress .......................................................................................................... 7-156

lan.status.port.dst .................................................................................................................. 7-157

lan.status.port.rawsocket ...................................................................................................... 7-157

lan.status.port.telnet .............................................................................................................. 7-158

lan.status.port.vxi11 .............................................................................................................. 7-158

lan.status.speed .................................................................................................................... 7-159

lan.status.subnetmask .......................................................................................................... 7-159

lan.timedwait ................................ ................................ ......................................................... 7-160

lan.trigger[N].assert() ............................................................................................................ 7-161

lan.trigger[N].clear() .............................................................................................................. 7-161

lan.trigger[N].connect() .......................................................................................................... 7-162

lan.trigger[N].connected ........................................................................................................ 7-163

lan.trigger[N].disconnect() ..................................................................................................... 7-164

lan.trigger[N].EVENT_ID ....................................................................................................... 7-164

lan.trigger[N].ipaddress ......................................................................................................... 7-165

lan.trigger[N].mode ................................................................................................................ 7-166

lan.trigger[N].overrun ............................................................................................................ 7-167

lan.trigger[N].protocol ................................................................ ................................ ............ 7-168

lan.trigger[N].pseudostate ..................................................................................................... 7-169

lan.trigger[N].stimulus ........................................................................................................... 7-170

lan.trigger[N].wait() ................................................................................................................ 7-171

localnode.autolinefreq ........................................................................................................... 7-172

localnode.description ............................................................................................................ 7-173

localnode.license ................................................................................................................... 7-174

localnode.linefreq .................................................................................................................. 7-174

localnode.model .................................................................................................................... 7-175

localnode.password .............................................................................................................. 7-175

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

localnode.passwordmode ..................................................................................................... 7-176

localnode.prompts ................................................................................................................. 7-177

localnode.prompts4882 ......................................................................................................... 7-178

localnode.reset() ................................................................................................................... 7-179

localnode.revision ................................................................................................................. 7-180

localnode.serialno ................................................................................................................. 7-180

localnode.showerrors ............................................................................................................ 7-181

makegetter() .......................................................................................................................... 7-182

makesetter() .......................................................................................................................... 7-183

meminfo() .............................................................................................................................. 7-184

node[N].execute() .................................................................................................................. 7-185

node[N].getglobal() ................................................................................................................ 7-186

node[N].setglobal() ................................................................................................................ 7-187

opc() ................................................................................................ ...................................... 7-188

os.remove() ........................................................................................................................... 7-188

os.rename() ........................................................................................................................... 7-189

os.time() ................................................................................................................................ 7-189

print() ..................................................................................................................................... 7-190

printbuffer()............................................................................................................................ 7-191

printnumber() ......................................................................................................................... 7-192

PulseIMeasureV() ................................................................................................................. 7-193

PulseVMeasureI() ................................................................................................................. 7-194

QueryPulseConfig() ............................................................................................................... 7-195

reset() .................................................................................................................................... 7-197

savebuffer() ........................................................................................................................... 7-198

script.anonymous .................................................................................................................. 7-199

script.delete() ........................................................................................................................ 7-200

script.factory.catalog() ........................................................................................................... 7-200

script.load() ........................................................................................................................... 7-201

script.new()............................................................................................................................ 7-202

script.newautorun() ............................................................................................................... 7-203

script.restore() ....................................................................................................................... 7-204

script.run() ............................................................................................................................. 7-204

script.user.catalog() ............................................................................................................... 7-205

scriptVar.autorun ................................................................................................................... 7-206

scriptVar.list() ........................................................................................................................ 7-207

scriptVar.name ...................................................................................................................... 7-208

scriptVar.run() ....................................................................................................................... 7-209

scriptVar.save() ..................................................................................................................... 7-210

scriptVar.source .................................................................................................................... 7-211

serial.baud............................................................................................................................. 7-212

serial.databits ........................................................................................................................ 7-213

serial.flowcontrol ................................................................................................................... 7-214

serial.parity ............................................................................................................................ 7-215

serial.read() ........................................................................................................................... 7-216

serial.write() ........................................................................................................................... 7-217

settime() ................................................................................................................................ 7-218

settimezone() ........................................................................................................................ 7-219

setup.poweron ....................................................................................................................... 7-220

setup.recall() ......................................................................................................................... 7-221

setup.save() .......................................................................................................................... 7-222

smuX.abort() ......................................................................................................................... 7-223

smua.buffer.getstats() ........................................................................................................... 7-223

smuX.buffer.recalculatestats() ............................................................................................... 7-225

smuX.cal.adjustdate .............................................................................................................. 7-226

smuX.cal.date ....................................................................................................................... 7-227

smuX.cal.due ........................................................................................................................ 7-228

smuX.cal.fastadc() ................................................................................................................ 7-229

smuX.cal.lock() ...................................................................................................................... 7-230

smuX.cal.password ............................................................................................................... 7-231

smuX.cal.polarity ................................................................................................................... 7-232

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

smuX.cal.restore() ................................................................................................................. 7-233

smuX.cal.save() .................................................................................................................... 7-234

smuX.cal.state ....................................................................................................................... 7-235

smuX.cal.unlock() .................................................................................................................. 7-236

smuX.contact.calibratehi() ..................................................................................................... 7-236

smuX.contact.calibratelo() ..................................................................................................... 7-238

smuX.contact.check() ............................................................................................................ 7-239

smuX.contact.r() .................................................................................................................... 7-240

smuX.contact.speed .............................................................................................................. 7-241

smuX.contact.threshold ......................................................................................................... 7-242

smuX.makebuffer() ................................................................................................................ 7-243

smuX.measure.adc ............................................................................................................... 7-243

smuX.measure.autorangeY................................................................................................... 7-244

smuX.measure.autozero ....................................................................................................... 7-245

smuX.measure.calibrateY() ................................................................................................... 7-246

smuX.measure.count ............................................................................................................ 7-247

smuX.measure.delay ............................................................................................................ 7-248

smuX.measure.delayfactor.................................................................................................... 7-249

smuX.measure.filter.count..................................................................................................... 7-250

smuX.measure.filter.enable................................................................................................... 7-251

smuX.measure.filter.type ...................................................................................................... 7-252

smua.measure.highcrangedelayfactor .................................................................................. 7-253

smuX.measure.interval ......................................................................................................... 7-254

smuX.measure.lowrangeY .................................................................................................... 7-255

smuX.measure.nplc .............................................................................................................. 7-256

smua.measure.overlappedY() ............................................................................................... 7-257

smuX.measure.rangeY ......................................................................................................... 7-258

smua.measure.rel.enableY ................................................................................................... 7-259

smua.measure.rel.levelY ....................................................................................................... 7-260

smuX.measure.Y() ................................................................................................................ 7-261

smuX.measureYandstep()..................................................................................................... 7-262

smuX.nvbufferY ..................................................................................................................... 7-263

smuX.reset() .......................................................................................................................... 7-264

smuX.savebuffer() ................................................................................................................. 7-265

smuX.sense .......................................................................................................................... 7-266

smuX.source.autorangeY ...................................................................................................... 7-267

smuX.source.calibrateY() ...................................................................................................... 7-268

smuX.source.compliance ...................................................................................................... 7-269

smuX.source.delay ................................................................................................................ 7-270

smuX.source.func ................................................................................................................. 7-271

smuX.source.highc ................................................................................................................ 7-271

smuX.source.levelY .............................................................................................................. 7-272

smuX.source.limitY ............................................................................................................... 7-273

smuX.source.lowrangeY ....................................................................................................... 7-274

smuX.source.offfunc ............................................................................................................. 7-275

smuX.source.offlimitY ........................................................................................................... 7-276

smuX.source.offmode ........................................................................................................... 7-277

smuX.source.output .............................................................................................................. 7-278

smuX.source.outputenableaction .......................................................................................... 7-279

smuX.source.rangeY ............................................................................................................. 7-280

smuX.source.settling ................................................................................................ ............. 7-281

smuX.source.sink .................................................................................................................. 7-282

smuX.trigger.arm.count ......................................................................................................... 7-283

smuX.trigger.arm.set() .......................................................................................................... 7-284

smuX.trigger.arm.stimulus..................................................................................................... 7-285

smuX.trigger.ARMED_EVENT_ID ........................................................................................ 7-286

smuX.trigger.autoclear .......................................................................................................... 7-287

smuX.trigger.count ................................................................................................................ 7-287

smuX.trigger.endpulse.action ................................................................................................ 7-289

smuX.trigger.endpulse.set() .................................................................................................. 7-289

smuX.trigger.endpulse.stimulus ............................................................................................ 7-291

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

smuX.trigger.endsweep.action .............................................................................................. 7-292

smuX.trigger.IDLE_EVENT_ID ............................................................................................. 7-293

smuX.trigger.initiate() ............................................................................................................ 7-294

smuX.trigger.measure.action ................................................................................................ 7-295

smuX.trigger.measure.set() ................................................................................................... 7-296

smua.trigger.measure.stimulus ............................................................................................. 7-297

smuX.trigger.measure.Y() ..................................................................................................... 7-298

smuX.trigger.MEASURE_COMPLETE_EVENT_ID .............................................................. 7-299

smuX.trigger.PULSE_COMPLETE_EVENT_ID .................................................................... 7-299

smuX.trigger.source.action.................................................................................................... 7-300

smuX.trigger.source.limitY .................................................................................................... 7-301

smuX.trigger.source.linearY() ................................................................................................ 7-302

smuX.trigger.source.listY() .................................................................................................... 7-303

smuX.trigger.source.logY().................................................................................................... 7-304

smuX.trigger.source.set() ...................................................................................................... 7-306

smuX.trigger.source.stimulus ................................................................................................ 7-307

smuX.trigger.SOURCE_COMPLETE_EVENT_ID ................................................................ 7-308

smuX.trigger.SWEEP_COMPLETE_EVENT_ID ................................................................... 7-309

smua.trigger.SWEEPING_EVENT_ID .................................................................................. 7-309

status.condition ..................................................................................................................... 7-311

status.measurement.* ........................................................................................................... 7-313

status.measurement.buffer_available.* ................................................................................. 7-315

status.measurement.current_limit.* ....................................................................................... 7-317

status.measurement.instrument.* .......................................................................................... 7-318

status.measurement.instrument.smuX.* ............................................................................... 7-319

status.measurement.reading_overflow.* ............................................................................... 7-321

status.measurement.sink_limit.* ............................................................................................ 7-323

status.measurement.voltage_limit.* ...................................................................................... 7-324

status.node_enable ............................................................................................................... 7-325

status.node_event ................................................................................................................. 7-327

status.operation.* .................................................................................................................. 7-329

status.operation.calibrating.* ................................................................................................. 7-332

status.operation.instrument.*................................................................................................. 7-333

status.operation.instrument.digio.* ........................................................................................ 7-335

status.operation.instrument.digio.trigger_overrun.* ............................................................... 7-337

status.operation.instrument.lan.* ........................................................................................... 7-339

status.operation.instrument.lan.trigger_overrun.* .................................................................. 7-341

status.operation.instrument.smuX.* ...................................................................................... 7-343

status.operation.instrument.smuX.trigger_overrrun.* ............................................................ 7-345

status.operation.instrument.trigger_blender.*........................................................................ 7-347

status.operation.instrument.trigger_blender.trigger_overrun.* .............................................. 7-349

status.operation.instrument.trigger_timer.* ........................................................................... 7-351

status.operation.instrument.trigger_timer.trigger_overrun.* .................................................. 7-352

status.operation.instrument.tsplink.* ..................................................................................... 7-354

status.operation.instrument.tsplink.trigger_overrun.* ............................................................ 7-356

status.operation.measuring.*................................................................................................. 7-358

status.operation.remote.* ...................................................................................................... 7-359

status.operation.sweeping.* .................................................................................................. 7-361

status.operation.trigger_overrun.* ......................................................................................... 7-362

status.operation.user.* .......................................................................................................... 7-365

status.questionable.* ............................................................................................................. 7-367

status.questionable.calibration.* ............................................................................................ 7-369

status.questionable.instrument.* ........................................................................................... 7-370

status.questionable.instrument.smuX.* ................................................................................. 7-371

status.questionable.over_temperature.* ................................................................................ 7-373

status.questionable.unstable_output.* .................................................................................. 7-375

status.request_enable ................................................................ ................................ ........... 7-376

status.request_event ............................................................................................................. 7-378

status.reset() ................................ ................................ ......................................................... 7-380

status.standard.* ................................................................................................................... 7-381

status.system.* ...................................................................................................................... 7-383

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

status.system2.* .................................................................................................................... 7-385

status.system3.* .................................................................................................................... 7-388

status.system4.* .................................................................................................................... 7-390

status.system5.* .................................................................................................................... 7-392

SweepILinMeasureV() ........................................................................................................... 7-394

SweepIListMeasureV() .......................................................................................................... 7-395

SweepILogMeasureV() ......................................................................................................... 7-396

SweepVLinMeasureI() ........................................................................................................... 7-398

SweepVListMeasureI() .......................................................................................................... 7-399

SweepVLogMeasureI() ......................................................................................................... 7-400

timer.measure.t() ................................................................................................................... 7-402

timer.reset() ........................................................................................................................... 7-403

trigger.blender[N].clear() ....................................................................................................... 7-403

trigger.blender[N].EVENT_ID ................................................................................................ 7-404

trigger.blender[N].orenable.................................................................................................... 7-405

trigger.blender[N].overrun ..................................................................................................... 7-406

trigger.blender[N].reset() ....................................................................................................... 7-407

trigger.blender[N].stimulus[M] ............................................................................................... 7-407

trigger.blender[N].wait() ......................................................................................................... 7-409

trigger.clear() ......................................................................................................................... 7-410

trigger.EVENT_ID ................................................................................................................. 7-410

trigger.timer[N].clear() ........................................................................................................... 7-411

trigger.timer[N].count ............................................................................................................. 7-412

trigger.timer[N].delay ............................................................................................................. 7-412

trigger.timer[N].delaylist ........................................................................................................ 7-413

trigger.timer[N].EVENT_ID .................................................................................................... 7-414

trigger.timer[N].overrun ......................................................................................................... 7-415

trigger.timer[N].passthrough .................................................................................................. 7-416

trigger.timer[N].reset() ........................................................................................................... 7-417

trigger.timer[N].stimulus ........................................................................................................ 7-418

trigger.timer[N].wait() ............................................................................................................. 7-419

trigger.wait() ................................ ................................ .......................................................... 7-420

tsplink.group .......................................................................................................................... 7-421

tsplink.master ........................................................................................................................ 7-422

tsplink.node ........................................................................................................................... 7-423

tsplink.readbit() ...................................................................................................................... 7-424

tsplink.readport() ................................................................................................................... 7-425

tsplink.reset() ......................................................................................................................... 7-426

tsplink.state ........................................................................................................................... 7-427

tsplink.trigger[N].assert() ....................................................................................................... 7-428

tsplink.trigger[N].clear() ......................................................................................................... 7-429

tsplink.trigger[N].EVENT_ID .................................................................................................. 7-430

tsplink.trigger[N].mode .......................................................................................................... 7-431

tsplink.trigger[N].overrun ....................................................................................................... 7-433

tsplink.trigger[N].pulsewidth .................................................................................................. 7-434

tsplink.trigger[N].release() ..................................................................................................... 7-435

tsplink.trigger[N].reset() ......................................................................................................... 7-436

tsplink.trigger[N].stimulus ...................................................................................................... 7-437

tsplink.trigger[N].wait() .......................................................................................................... 7-438

tsplink.writebit() ..................................................................................................................... 7-439

tsplink.writeport() ................................................................................................................... 7-440

tsplink.writeprotect ................................................................................................................ 7-441

tspnet.clear() ................................ ................................ ......................................................... 7-442

tspnet.connect() .................................................................................................................... 7-443

tspnet.disconnect() ................................................................................................................ 7-444

tspnet.execute() .................................................................................................................... 7-445

tspnet.idn() ............................................................................................................................ 7-446

tspnet.read() .......................................................................................................................... 7-447

tspnet.readavailable() ............................................................................................................ 7-448

tspnet.reset() ......................................................................................................................... 7-449

tspnet.termination() ............................................................................................................... 7-449

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

tspnet.timeout ........................................................................................................................ 7-450

tspnet.tsp.abort() ................................................................................................................... 7-451

tspnet.tsp.abortonconnect ..................................................................................................... 7-452

tspnet.tsp.rbtablecopy() ......................................................................................................... 7-453

tspnet.tsp.runscript() ............................................................................................................. 7-454

tspnet.write() ......................................................................................................................... 7-455

userstring.add() ..................................................................................................................... 7-456

userstring.catalog() ............................................................................................................... 7-457

userstring.delete() ................................................................................................................. 7-458

userstring.get() ...................................................................................................................... 7-458

waitcomplete() ....................................................................................................................... 7-459

Troubleshooting guide ............................................................................................ 8-1

Introduction .......................................................................................................................... 8-1

Error levels ........................................................................................................................... 8-1

Effects of errors on scripts ................................................................................................... 8-2

Retrieving errors ................................................................................................................... 8-2

Error summary list ................................................................................................................ 8-3

LAN troubleshooting suggestions ........................................................................................ 8-8

Frequently asked questions .................................................................................... 9-1

How do I display the instrument's serial number? ............................................................... 9-1

How do I optimize performance? ......................................................................................... 9-2

Disabling autozero to increase speed ....................................................................................... 9-2

How do I upgrade the firmware? .......................................................................................... 9-2

How do I use the digital I/O port? ......................................................................................... 9-3

How do I trigger other instruments? ..................................................................................... 9-3

Triggering a scanner ................................................................................................................. 9-3

Interactive trigger programming ................................................................................................ 9-4

More information about triggering ............................................................................................. 9-4

How do I generate a GPIB service request?........................................................................ 9-4

Setting up a service request ...................................................................................................... 9-4

Service request programming example ..................................................................................... 9-5

Polling for SRQs ........................................................................................................................ 9-5

How do I store measurements in nonvolatile memory? ....................................................... 9-5

When should I change the output-off state? ........................................................................ 9-6

How do I make contact check measurements? ................................................................... 9-6

How do I make low-current measurements? ....................................................................... 9-7

Low-current connections ........................................................................................................... 9-7

Low-current measurement programming example .................................................................... 9-9

How can I change the line frequency or voltage? ................................................................ 9-9

Where can I get the LabVIEW driver? ................................................................................. 9-9

What should I do if I get an 802 interlock error? ................................................................ 9-10

Why is the reading value 9.91e37? .................................................................................... 9-10

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

Next steps ............................................................................................................... 10-1

Additional Model 2651A information .................................................................................. 10-1

Maintenance ........................................................................................................... 11-1

Introduction ........................................................................................................................ 11-1

Line fuse replacement ........................................................................................................ 11-1

Front-panel tests ................................................................................................................ 11-2

Keys test ................................................................................................................................. 11-2

Display patterns test ................................................................................................................ 11-3

Upgrading the firmware ...................................................................................................... 11-4

Using TSB to upgrade the firmware ........................................................................................ 11-5

Calibration .............................................................................................................. 12-1

Verification ......................................................................................................................... 12-1

Calibration test requirements .................................................................................................. 12-2

Restoring factory defaults........................................................................................................ 12-4

Performing the calibration test procedures .............................................................................. 12-5

Current source accuracy ......................................................................................................... 12-7

Current measurement accuracy .............................................................................................. 12-9

-45 A high speed ADC pulse verification script ..................................................................... 12-11

Voltage source accuracy ....................................................................................................... 12-13

Voltage measurement accuracy ............................................................................................ 12-14

Adjustment ....................................................................................................................... 12-16

Environmental conditions ...................................................................................................... 12-16

Adjustment considerations .................................................................................................... 12-17

Calibration adjustment overview ........................................................................................... 12-19

Calibration commands quick reference ................................................................................. 12-21

Adjustment procedure ........................................................................................................... 12-22

LAN concepts and settings ................................................................................... 13-1

Overview ............................................................................................................................ 13-1

Establishing a point-to-point connection ............................................................................ 13-1

Step 1: Identify and record the existing IP configuration ......................................................... 13-2

Step 2: Disable DHCP to use the existing computer IP address ............................................. 13-3

Step 3: Configure the LAN settings of the instrument ............................................................. 13-4

Step 4: Install the crossover cable .......................................................................................... 13-5

Step 5: Access the web interface of the instrument ................................................................ 13-6

Connecting to the LAN ....................................................................................................... 13-6

Setting the LAN configuration method ..................................................................................... 13-7

Setting the IP address ................................................................ ................................ ............. 13-7

Setting the gateway ................................................................................................................. 13-8

Setting the subnet mask .......................................................................................................... 13-8

Configuring the domain name system (DNS) .......................................................................... 13-8

LAN speeds ........................................................................................................................ 13-9

Duplex mode .................................................................................................................... 13-10

Viewing LAN status messages ........................................................................................ 13-10

Viewing the network settings ........................................................................................... 13-11

Model 2651A High Power System SourceMeter® Instrument Reference Manual Table of contents

Confirming the active speed and duplex negotiation ............................................................. 13-12

Confirming port numbers ....................................................................................................... 13-12

Selecting a LAN interface protocol ................................................................................... 13-13

VXI-11 connection ................................................................................................................. 13-13

Raw socket connection ......................................................................................................... 13-13

Dead socket connection ........................................................................................................ 13-14

Telnet connection .................................................................................................................. 13-14

Logging LAN trigger events in the event log .................................................................... 13-17

Accessing the event log from the command interface ........................................................... 13-19

Common commands .............................................................................................. 14-1

Common command summary ............................................................................................ 14-1

Script command equivalents .............................................................................................. 14-3

Command reference .......................................................................................................... 14-3

Identification query: *IDN?....................................................................................................... 14-3

Operation complete and query: *OPC and *OPC? .................................................................. 14-4

Reset: *RST ................................................................ ............................................................ 14-4

Self-test query: *TST? ............................................................................................................. 14-4

Trigger: *TRG .......................................................................................................................... 14-4

Wait-to-continue: *WAI ................................................................ ............................................ 14-5

General bus commands ..................................................................................................... 14-5

REN ........................................................................................................................................ 14-5

IFC .......................................................................................................................................... 14-6

LLO ......................................................................................................................................... 14-6

GTL ......................................................................................................................................... 14-6

DCL ......................................................................................................................................... 14-6

SDC ........................................................................................................................................ 14-7

GET ......................................................................................................................................... 14-7

SPE, SPD................................................................................................................................ 14-7

Status model .......................................................................................................... 15-1

Overview ............................................................................................................................ 15-1

Status register set contents ..................................................................................................... 15-1

Queues ................................................................................................................................... 15-2

Status function summary ......................................................................................................... 15-4

Status model diagrams ........................................................................................................... 15-5

Clearing registers ............................................................................................................. 15-13

Programming and reading registers ................................................................................. 15-13

Programming enable and transition registers ........................................................................ 15-14

Reading registers .................................................................................................................. 15-14

Status byte and service request (SRQ) ........................................................................... 15-15

Status Byte Register ............................................................................................................. 15-15

Service Request Enable Register ......................................................................................... 15-17

Serial polling and SRQ .......................................................................................................... 15-18

SPE, SPD (serial polling) ...................................................................................................... 15-18

Status byte and service request commands.......................................................................... 15-19

Enable and transition registers .............................................................................................. 15-19

Controlling node and SRQ enable registers .......................................................................... 15-19

Status register sets .......................................................................................................... 15-20

System Summary Registers .................................................................................................. 15-20

Standard Event Register ....................................................................................................... 15-21

Operation Status Registers ................................................................................................... 15-23

Table of contents Model 2651A High Power System SourceMeter® Instrument Reference Manual

Questionable Status Registers .............................................................................................. 15-24

Measurement Event Registers .............................................................................................. 15-24

Register programming example ............................................................................................ 15-26

TSP-Link system status ................................................................................................... 15-26

Status model configuration example ..................................................................................... 15-26

Display character codes ........................................................................................ 16-1

Model 2651A display character codes ............................................................................... 16-1

In this section:

Welcome .................................................................................. 1-1

Extended warranty ................................................................... 1-1

Contact information .................................................................. 1-1

Customer documentation ......................................................... 1-2

Capabilities and features .......................................................... 1-3

Model-specific capabilities........................................................ 1-4

General information .................................................................. 1-4

Welcome

Thank you for choosing a Keithley Instruments product. The Model 2651A High Power System
SourceMeter® Instrument provides manufacturers of electronic components and semiconductor
devices with an instrument that combines source and measurement capabilities in a single instrument
called a source-measure unit (also called a SMU). This combination simplifies test processes by
eliminating synchronization and connection issues associated with multiple instrument solutions.
A Model 2651A provides a scalable, high throughput, highly cost-effective solution for precision dc,
pulse, and low frequency ac source-measure testing that also maintains code compatibility with the
Series 2600B instruments.

Extended warranty

Additional years of warranty coverage are available on many products. These valuable contracts
protect you from unbudgeted service expenses and provide additional years of protection at a fraction
of the price of a repair. Extended warranties are available on new and existing products. Contact your
local Keithley Instruments office, sales partner, or distributor for details.

Contact information

If you have any questions after you review the information in this documentation, please contact your
local Keithley Instruments office, sales partner, or distributor. You can also call the Tektronix
corporate headquarters (toll-free inside the U.S. and Canada only) at 1-800-833-9200. For worldwide
contact numbers, visit tek.com/contact-us.

Section 1

Introduction

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1-2 2651A-901-01 Rev. C October 2021

Customer documentation

The documentation for the Model 2651A includes a Quick Start Guide, User's Manual, and Reference
Manual. The Model 2651A Quick Start Guide is provided as a hard copy with the instrument. You can
also access it from tek.com/keithley as an Adobe Acrobat PDF file.

Quick Start Guide: Provides unpacking instructions, describes basic connections, and reviews basic
operation information. If you are new to Keithley Instruments equipment, refer to the Quick Start
Guide to take the steps needed to unpack, set up, and verify operation.

User's Manual: Provides detailed applications to help you achieve success with your Model 2651A. It
provides information about the front panel to familiarize you with the instrument. It also presents an
overview of each application, followed by instructions to complete the application using the front panel
and TSP code.

Reference Manual: Includes advanced operation topics and maintenance information. Programmers
looking for a command reference and users looking for an in-depth description of the way the
instrument works (including troubleshooting and optimization) should refer to the Reference Manual.

Organization of manual sections

The information in this manual is organized into the following major categories:

• General operation: Describes the components of the instrument and basic operation.

• Functions and features: Describes features and functions, such as relative offset, filters,

reading buffers, triggering, the digital I/O port, and TSP-Link trigger lines.

• Theory of operation: Describes the internal circuitry and software of the Model 2651A in detail.

• Remote commands: Describes the basics of using remote commands to control the instrument,

including descriptions of the factory scripts.

• Instrument programming: Describes how to control the instrument using TSP, TSB and TSB

Embedded, TSP-Link system expansion, and TSP-Net.

• Command reference: Programming notes and an alphabetical listing of all commands available

for the Model 2651A.

• Troubleshooting guide: Description of the error queue and basic LAN troubleshooting.

• Frequently asked questions (FAQs): Information that addresses commonly asked questions.

• Next steps: Contains sources of additional information.

• Maintenance: Information on instrument maintenance, including line fuse replacement and

firmware upgrades.

• Calibration: How to verify and adjust the Model 2651A.

• LAN concepts and settings: How to set up the Model 2651A for use on a local area network.

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2651A-901-01 Rev. C October 2021 1-3

• Common commands: Descriptions of IEEE Std. 488.2 common commands.

• Status model: Description of the Model 2651A status model.

• Display character codes: Listing of the decimal values for the display character codes and their

corresponding displays.

Capabilities and features

Model 2651A High Power System SourceMeter® Instruments have the following features:

• Resistance and power measurement functions

• Four-quadrant sink or source operation

• Contact check function

• High-capacitance mode for load impedance up to 50 µF (microfarads)

• Linear, logarithmic, and custom sweeping and pulsing

• Filtering to reduce reading noise

• High-speed sampling fast analog-to-digital converter (ADC); the fast ADC uses a hardware buffer

that can store up to 5,000 readings in a single measure action

• A trigger model that supports extensive triggering and synchronization schemes at hardware

speeds

• Internal memory that stores five user setup options

• Dedicated reading buffers that can each store and recall over 140,000 measurements; additional

dynamic reading buffers can be created

• USB flash drive access for saving data buffers, test scripts, and user setups

• Digital I/O port that allows the Model 2651A to control other devices

• Compatible with Keithley IVy, a wireless I-V characterization tool

• LXI

®

• Embedded TSP scripting engine that is accessible from any host interface; responds to

high-speed test scripts comprised of instrument control commands

• TSP-Link

®

expansion bus that allows TSP-enabled instruments to trigger and communicate with
each other; advanced Test Script Processor (TSP®) scripting engine features enable parallel
script execution across the TSP-Link network

• Supports IEEE-488 (GPIB), RS-232, and ethernet local area network (LAN) connections

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Model-specific capabilities

Additional source and measure features:

• Source ± dc voltage from 1 mV to 40.4 V

• Source ± dc current from 10 pA to 20.2 A

• Source ± pulse current up to 50 A

• Measure ± pulse current up to 50 A

• Measure ± dc voltage from 1 mV to 40.4 V

• Measure ± dc current from 10 pA to 20.2 A

General information

Displaying the serial number

The instrument serial number is on a label on the rear panel of the instrument. You can also access
the serial number from the front panel using the front-panel keys and menus.

To display the serial number on the front panel:

1. If the Model 2651A is in remote operation, press the EXIT (LOCAL) key once to place the
instrument in local operation.

2. Press the MENU key.

3. Use the navigation wheel to scroll to the SYSTEM-INFO menu item.

4. Press the ENTER key. The SYSTEM INFORMATION menu is displayed.

5. Scroll to the SERIAL# menu item.

6. Press the ENTER key. The Model 2651A serial number is displayed.

In this section:

General ratings ......................................................................... 2-1

Controls, indicators, and connectors ........................................ 2-2

Cooling vents ........................................................................... 2-8

Starting up your instrument ...................................................... 2-9

System information ................................................................ 2-11

Menu overview ....................................................................... 2-11

Beeper ................................................................................... 2-18

Display mode ......................................................................... 2-19

Basic operation ...................................................................... 2-19

DUT test connections ................................ ............................. 2-45

DUT connection settings ........................................................ 2-64

USB storage overview ............................................................ 2-69

Displayed error and status messages .................................... 2-71

Range .................................................................................... 2-71

Digits ...................................................................................... 2-77

Speed ..................................................................................... 2-78

Remote communications interfaces ....................................... 2-80

General ratings

The Model 2651A instrument's general ratings and connections are listed in the following table.

Category

Specification

Supply voltage range

100 Vac to 240 Vac, 50 Hz or 60 Hz, 550 VA maximum

Input and output connections

See Rear panel (on page 2-6)

Environmental conditions

For indoor use only:

Altitude: Maximum 2000 meters (6562 feet) above sea level
Operating: 0 °C to 50 °C, 70% relative humidity up to 35 °C. Derate 3%

relative humidity/°C, 35 °C to 50 °C
Storage: −25 °C to 65 °C

Section 2

General operation

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Controls, indicators, and connectors

Model 2651A controls, indicators, and the USB port are on the front panel (on page 2-2). Make
connections to the Model 2651A through connectors on the rear panel (on page 2-6).

Front panel

The front panel of the Model 2651A is shown below. The descriptions of the front-panel controls, USB
port, and indicators follow the figure.

Figure 1: Front panel Model 2651A

1. Power switch, display and configuration keys

Power switch. The in position turns the Model 2651A on (I); the out position turns it off
(O).
Toggles between the source-measure display and the user message display.

Configures a function or operation.

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2. SMU setup, performance control, special operation, and numbers

SMU (source-measure unit) setup
SRC

Selects the source function (voltage or current) and places the cursor in the source field
for editing.

MEAS

Cycles through measure functions (voltage, current, resistance, or power).

LIMIT

Places the cursor in the compliance limit field for editing. Also selects the limit value to
edit (voltage, current, or power).

MODE

Selects a meter mode (I-METER, V-METER, OHM-METER, or WATT-METER).

Performance control
DIGITS

Sets the display resolution (4½, 5½, or 6½ digits).

SPEED

Sets the measurement speed (FAST, MEDium, NORMAL, HI-ACCURACY, or OTHER).
Setting the speed selects either the fast or integrating A/D converter. When FAST is
selected, the fast A/D converter is used; any other selection (MEDium, NORMAL,
HI-ACCURACY, or OTHER) selects the integrating A/D converter. When the integrating
A/D converter is selected, the measurement speed and accuracy are set by controlling
the measurement aperture. Also see Speed (on page 2-78).

REL

Controls relative measurements, which allows a baseline value to be subtracted from a
reading.

FILTER

Enables or disables the digital filter. You can use this filter to reduce reading noise.

Special operation

LOAD

Loads a test for execution (FACTORY, USER, or SCRIPTS).

RUN

Runs the last selected factory or user-defined test.

STORE

Accesses reading buffers and makes readings:

▪ TAKE_READINGS: Use to make readings and store them in a reading buffer.
▪ SAVE: Use to save a reading buffer to nonvolatile memory or to a user-installed

flash drive (USB1) in CSV or XML format.

Readings can include measurements, source values, and timestamp values.

RECALL

Recalls information (DATA or STATISTICS) stored in a reading buffer:

▪ DATA: Includes stored readings, and if configured, source values and timestamp

values.

▪ STATISTICS: Includes MEAN, STD DEV, SAMPLE SIZE, MINIMUM,

MAXIMUM, PK-PK.

TRIG

Triggers readings.

MENU

Accesses the main menu (on page 2-13). You can use the main menu to configure
many functions and features.

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EXIT

Cancels the selection and returns to the previous menu or display. Also used as a
LOCAL key to take the instrument out of remote operation.

ENTER

Accepts the selection and moves to the next choice or exits the menu.

Numbers

Number keys

When enabled and in EDIT mode, the number keys (0 to 9, +/-, 0000) allow direct
numeric entry. Press the navigation wheel to enter EDIT mode. For more information,
see Setting a value (on page 2-16).

3. Range keys

Selects the next higher source or measure range.

Enables or disables source or measure autorange.

Selects the next lower source or measure range.

In addition to selecting range functions, the up and down range keys change the format
for numbers that are not ranges, such as the limit value.

4. Cursor keys

Use the CURSOR keys to move the cursor left or right. When the cursor is on the
source or compliance value digit, press the navigation wheel to enter edit mode, and
turn the navigation wheel to edit the value. Press the navigation wheel again when you
finish editing.
Use the CURSOR keys or the navigation wheel to move through menu items. To view a
menu value, use the CURSOR keys for cursor control, and then press the navigation
wheel to view the value or submenu item.

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5. Navigation wheel

Turn the navigation wheel to:

▪ Move the cursor to the left and the right (the cursor indicates the selected value

or item)

▪ While in edit mode, increase or decrease a selected source or compliance value

Push the navigation wheel to:

▪ Enable or disable edit mode for the selected source or compliance value
▪ Open menus and submenu items
▪ Select a menu option or a value

6. Output control

Turns the source output on or off. The source output is on when this switch is
illuminated (blue).

7. USB port

Use the USB port to connect a USB flash drive to the instrument. You can use the USB flash drive
to store reading buffer data, scripts, and user setups. You can also use it to upgrade the firmware.

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8. Display indicators (not shown)

The items listed below represent the possible display indicators and their meanings.

Indicator

Meaning

4W

Remote (4-wire) sense is selected

AUTO

Source or measure autorange is selected

EDIT

Instrument is in editing mode

ERR

Questionable reading or invalid calibration step

FILT

Digital filter is enabled

LSTN

Instrument is addressed to listen

REL

Relative mode is enabled

REM

Instrument is in remote mode

SRQ

Service request is asserted

TALK

Instrument is addressed to talk

* (asterisk)

Readings are being stored in the buffer

Rear panel

The rear panel of Model 2651A is shown below. The descriptions of the rear-panel components follow
the figure.

Figure 2: Rear panel Model 2651A

1. RS-232

Female DB-9 connector. For RS-232 operation, use a straight-through (not null
modem) DB-9 shielded cable for connection to a computer.

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2. DIGITAL I/O

Female DB-25 connector. Includes fourteen digital input or output pins, seven
GND pins, three +5 V pins, and one pin for output enable. For more information,
see Digital I/O (on page 3-92).
Use a cable equipped with a male DB-25 connector (Keithley Instruments
Model 7709-308).

3. Power module

Contains the ac line receptacle and power line fuse. The instrument can operate
on line voltages of 100 V to 240 Vac at line frequencies of 50 Hz or 60 Hz.

4. IEEE-488

Connector for IEEE-488 (GPIB) operation. Use a
shielded cable such as the Keithley Instruments
Model 7007-1.

5. LAN

RJ-45 connector for a local area network (LAN). The
LAN interface supports Auto-MDIX, so you can use
either a CAT-5e crossover cable or a normal CAT-5e
straight-through cable.

6. TSP-link

Expansion interface that allows a Model 2651A and other TSP-enabled
instruments to trigger and communicate with each other. Use a category 5e or
higher LAN crossover cable.

7. Chassis ground

Ground screw for connections to chassis ground.

8. Cooling exhaust vent

Exhaust vent for the internal cooling fan. Keep the vent free of obstructions to
prevent overheating. Also see Cooling vents (on page 2-8).

9. Terminal connector

This connector provides input/output connections for sense (S HI/S LO) and
guard (G). Connections are as follows:
S LO = Sense LO
G = Guard
S HI = Sense HI

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10. OUTPUT connector (40 V, 50 A maximum)

This connector provides HI/LO connection points for currents. Connections are
as follows:
LO = Input/Output LO
HI = Input/Output HI

Cooling vents

The Model 2651A has top and side intake vents and a rear exhaust vent. The rear exhaust vent and
either the top or both side intake vents must be unobstructed to properly dissipate heat.

Excessive heat could damage the Model 2651A and degrade its performance. Only operate the
Model 2651A in an environment where the ambient temperature does not exceed 50 °C.

Do not place a container of liquid (water or coffee, for instance) on the top cover. If it spills, the liquid
may enter the case through the vents and cause severe damage.

To prevent damaging heat build-up and ensure specified performance, use the
following guidelines.

The rear exhaust vent and either the top or both side intake vents must be unobstructed to
properly dissipate heat. Even partial blockage could impair proper cooling.

Do not position any devices adjacent to the Model 2651A that force air (heated or unheated)
toward its cooling vents or surfaces. This additional airflow could compromise accuracy.

When rack mounting the Model 2651A, make sure there is adequate airflow around both sides
to ensure proper cooling. Adequate airflow enables air temperatures within approximately
one inch of the Model 2651A surfaces to remain within specified limits under all operating
conditions.

If high power dissipation equipment is rack mounted next to the Model 2651A, it could cause
excessive heating. To produce specified Model 2651A accuracies, maintain the specified
ambient temperature around the surfaces of the Model 2651A. In rack configurations with
convection cooling only, proper cooling practice places the hottest non-precision equipment
(for example, the power supply) at the top of the rack away from and above precision
equipment (such as the Model 2651A).

Mount precision equipment as low as possible in the rack, where temperatures are coolest.
You can add space panels above and below the Model 2651A to help provide adequate
airflow.

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Starting up your instrument

The following topics describe how to power your instrument on and off, place the instrument in
standby, configure the line frequency, and replace the line fuse.

Procedure

The Model 2651A operates from a line voltage of 100 V to 240 V at a frequency of 50 Hz or 60 Hz. At
the factory, each Model 2651A is configured to match the power line frequency appropriate for your
country (either 50 Hz or 60 Hz). Make sure the operating voltage in your area is compatible.

Follow the procedure below to connect the Model 2651A to line power and turn on the instrument.

Operating the instrument on an incorrect line voltage may cause damage to the instrument,
possibly voiding the warranty.

To turn a Model 2651A on and off:

1. Before plugging in the power cord, make sure that the front panel POWER switch is in the off (O)
position.

2. Connect the Model 2651A redundant protective earth (safety ground) on the Rear panel (on page
2-6).

3. Connect the female end of the supplied power cord to the ac receptacle on the rear panel.

The power cord supplied with the Model 2651A contains a separate protective earth (safety
ground) wire for use with grounded outlets. When proper connections are made, the
instrument chassis is connected to power-line ground through the ground wire in the power
cord. In addition, a redundant protective earth connection is provided through a screw on the
rear panel. This terminal should be connected to a known protective earth. In the event of a
failure, not using a properly grounded protective earth and grounded outlet may result in
personal injury or death due to electric shock.

Do not replace detachable mains supply cords with inadequately rated cords. Failure to use
properly rated cords may result in personal injury or death due to electric shock.

4. Connect the other end of the power cord to a grounded ac outlet.

5. To turn your instrument on, press the front panel POWER switch to place it in the on (I) position.

6. To turn your instrument off, press the front panel POWER switch to place it in the off (O) position.

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Placing the Model 2651A in standby

Placing the Model 2651A in standby does not place the instrument in a safe state (an interlock
(on page 3-98) is provided for this function).

When the instrument is on, the output may be placed in an active output state (output on) or a
standby mode (output off). From the front panel, pressing the OUTPUT ON/OFF control (see Output

control (on page 2-5)) toggles the output using the present instrument configuration. You can also

place the output in standby over the remote interface by sending the following command:

smua.source.output = 0

Even though the instrument is placed in standby, the output may not be actually off.

Warmup period

The Model 2651A must be turned on and allowed to warm up for at least two hours to achieve
rated accuracies.

Line frequency configuration

The instrument automatically detects the power line frequency (either 50 Hz or 60 Hz) at each
power-up. This detected line frequency is used for aperture (NPLC) calculations.

In noisy environments, you can manually configure the instrument to match the actual line frequency.

To configure the line frequency from the front panel:

1. Press the MENU key, then turn the navigation wheel to select LINE-FREQ, and then press the
ENTER key.

2. Turn the navigation wheel to select the appropriate frequency and then press the ENTER key. To
configure the instrument to automatically detect line frequency at each power-up, select AUTO.

3. Press the EXIT (LOCAL) key to back out of the menu structure.

To configure the line frequency from a remote interface:

Set the localnode.linefreq or the localnode.autolinefreq attribute. The following
programming example illustrates how to set the line frequency to 60 Hz:

localnode.linefreq = 60

The following programming example illustrates how to remotely configure the instrument to
automatically detect line frequency at each power-up:

localnode.autolinefreq = true

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Fuse replacement

The power receptacle contains a fuse drawer (refer to Rear panel (on page 2-6)). This fuse protects
the power-line input of the instrument. If the line fuse needs to be replaced, refer to Line fuse

replacement (on page 11-1).

System information

You can retrieve serial number, firmware revision, calibration dates, and memory usage
from the instrument.

To view the system information from the front panel:

1. Press the MENU key.

2. Select SYSTEM-INFO.

3. Select one of the following:

▪ FIRMWARE
▪ SERIAL#
▪ CAL
▪ MEMORY-USAGE

To retrieve system information from a remote interface:

To retrieve the firmware revision and serial number, send the *IDN? query (see Identification query:

*IDN? (on page 14-3) for more information).

To determine memory usage, see the meminfo() (on page 7-184) function.
To determine when calibration was last run, see smuX.cal.date (on page 7-227).
To determine when calibration is due, see smuX.cal.due (on page 7-228).

Menu overview

The following topics describe how to work with the front-panel menus.

Menu navigation

To navigate through the menus and submenus, the Model 2651A must not be in edit mode (the EDIT
indicator is not illuminated).

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Selecting menu items

To navigate the Main and Configuration menus, use the front-panel keys as follows:

• Press either CURSOR arrow key to highlight an option.

• Rotate the navigation wheel (clockwise or counterclockwise) to highlight an option.

• Press the ENTER key (or the navigation wheel) to select an option.

• Use the EXIT (LOCAL) key to cancel changes or to return to the previous menu or display.

For quick menu navigation, turn the navigation wheel to highlight an option and then press the
navigation wheel to select the highlighted option.

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Menu trees

You can configure instrument operation through the menus that are accessed from the front panel.

Main menu

The main menu structure is summarized in the following figure and table. For other menu items, see

Configuration menu (on page 2-15).

Figure 3: Main menu tree

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The following table contains descriptions of the main menu options and cross-references to related
information. To access a menu option, press the MENU key, turn the navigation wheel to move the
cursor to select an item, and press the navigation wheel.

Menu selection

Description

For more information, see:

SCRIPT

Saves and recalls users scripts

Manage scripts (on page 6-3)

- LOAD

Loads scripts into nonvolatile memory

- SAVE

Saves scripts

SETUP

Saves and recalls user and factory setup options

Saved setups (on page 2-42)

- SAVE

Saves user setup options

- RECALL

Recalls user setup options

- POWERON

Sets the configuration used during startup

GPIB

Configures the GPIB interface options

Remote communications interfaces (on

page 2-80), GPIB setup (on page 2-83)

- ADDRESS

Configures the address for the GPIB interface

- ENABLE

Enables and disables the GPIB interface

LAN

Configures the local area network (LAN)

Remote communications interfaces (on

page 2-80), LAN communications (on
page 2-81), LAN concepts and settings
(on page 2-81, on page 13-1)

- STATUS

Displays LAN connection status

- CONFIG

Configures the LAN IP address and gateway

- APPLY_SETTINGS

Applies changes made using the CONFIG menu

- RESET

Restores the default settings

- ENABLE

Enables and disables the LAN interface

RS232

Controls the options for the RS-232 interface

Remote communications interfaces (on

page 2-80), RS-232 interface operation
(on page 2-90)

- BAUD

Sets the baud rate

- BITS

Configures the number of bits

- PARITY

Sets the parity

- FLOW-CTRL

Configures the flow control

- ENABLE

Enables and disables the RS-232 interface

TSPLINK

Configures the instrument in a TSP-Link® network

TSP-Link system expansion interface

- NODE

Selects the instrument node identifier

- RESET

Resets the TSP-Link network

UPGRADE

Upgrades the firmware from a USB flash drive

Upgrading the firmware (on page 11-4)

DISPLAY

Accesses display functions

Front panel tests (on page 11-2)

- TEST

Runs the display test

See Numeric entry method in Setting a

value (on page 2-16)

- NUMPAD

Enables and disables the numeric keypad

DIGOUT

Controls digital outputs

Digital I/O (on page 3-92)

- DIG-IO-OUTPUT

Selects the digital I/O values

- WRITE-PROTECT

Write-protects specific digital I/O lines

BEEPER

Controls the key beeps

Beeper (on page 2-18)

- ENABLE

Enables the key beeps

- DISABLE

Disables the key beeps

LINE-FREQ

Configures the line frequency

Line frequency configuration (on page

2-10)

- 50Hz

Sets the line frequency to 50 Hz

- 60Hz

Sets the line frequency to 60 Hz

AUTO

Enables automatic line frequency detection during
start up

SYSTEM-INFO

Displays system information

System information (on page 2-11)

- FIRMWARE

Displays the version of firmware installed

- SERIAL#

Displays the serial number of the instrument

- CAL

Displays the last calibration date

- MEMORY-USAGE

Displays the memory usage in kilobytes

RESET-PASSWORD

Resets the system password

Password management (on page 6-41)

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Configuration menu

The configuration menu structure is summarized in the following figure and table. For directions on
navigating the menu, see Menu navigation (on page 2-11). For other menu items, see Main menu (on
page 2-13).

Figure 4: CONFIG menu tree

Press the EXIT (LOCAL) key to return to a previous menu.

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The following table contains descriptions of the configuration menus, as well as cross-references to
related information. To select a menu, press the CONFIG key and then the front-panel key associated
with the menu (see the description column in the following table).

To access, press the CONFIG
key and then:

Options

For more information, see:

SRC

V-source sense, low range;
I-source low range; sink; and
highC mode

Range (on page 2-71)

MEAS

V and I-measure sense, low
range; auto-zero

Range (on page 2-71)

LIMIT

V-source and I-source
compliance limits

Compliance limit (on page 2-20)

SPEED

Measurement speed (NPLC)

Speed (on page 2-78)

REL

Set relative values

Relative offset (on page 3-1)

FILTER

Control digital filter

Filters (on page 3-3)

OUTPUT ON/OFF

Set off-state, control digital
I/O

Output-off states (on page 2-65)

TRIG

Set trigger in, count, interval,
and delay

Triggering (on page 3-36)

STORE

Set buffer count and
destination

Source-measure concepts (on page 4-2)

Setting values

Through the front panel, you can adjust a value using either the Navigation wheel method or
Numeric entry method (using the keypad).

Setting a value

Navigation wheel method:

1. Use the CURSOR arrow keys (or turn the navigation wheel) to move the cursor to the digit that
needs to be changed.

2. Press the navigation wheel or the ENTER key to enter edit mode. The EDIT indicator is
illuminated.

3. Rotate the navigation wheel to set the appropriate value.

4. Press the ENTER key to select the value or press the EXIT (LOCAL) key to cancel the change.

5. To return to the main menu, press the EXIT (LOCAL) key.

Numeric entry method:

1. If the keypad is disabled, press the MENU key, then select DISPLAY > NUMPAD > ENABLE.

2. Use the CURSOR arrow keys (or turn the navigation wheel) to move the cursor to the value that
needs to be changed.

3. Press the navigation wheel or the ENTER key to enter edit mode. The EDIT indicator is
illuminated.

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4. Press any of the number keys (0-9, +/-, 0000) (see 2. SMU setup, performance control, special

operation, and numbers (on page 2-3)). The cursor moves to the next digit on the right.

5. Repeat the above steps as required to set the values.

6. Press the ENTER key to select the value or press the EXIT (LOCAL) key to cancel the change.

7. To return to the main menu, press the EXIT (LOCAL) key.

To set a value to zero, press the 0000 numeric entry key. To toggle the polarity of a value, press the

+/– numeric entry key.

Setting source and compliance values

When the Model 2651A is in the edit mode (EDIT indicator is on), the editing controls are used to set
source and compliance values. Note that when you edit the source value, source autoranging is
turned off and remains off until you turn it on again.

To cancel source editing, press the EXIT (LOCAL) key.

To edit the source value:

1. Press the SRC key. The cursor flashes in the source value field.

2. Use the CURSOR keys (or turn the navigation wheel) to move the cursor to the digit that needs to
be changed.

3. Press the navigation wheel or the ENTER key to edit the source value. The EDIT indicator is
illuminated.

4. Change the source value (see Setting a value (on page 2-16)).

The +/- key toggles the polarity. The 0000 key sets the value to 0.

5. When finished, press the ENTER key (the EDIT indicator is not illuminated).

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To edit compliance limit values:

1. Press the LIMIT key.

2. Select the type of compliance (CURRENT, VOLTAGE, or POWER).

3. Press the navigation wheel or the ENTER key to enter edit mode. The EDIT indicator is
illuminated.

4. Change the compliance value (see Setting a value (on page 2-16)).

5. When finished, press the ENTER key (the EDIT indicator is not illuminated).

The up and down range keys change the format of the limit value.

Beeper

The Model 2651A includes a beeper. When it is enabled, a beep indicates one of the following
actions have occurred:

• A front-panel key was pressed: A short beep, similar to a key click, is issued.

• The navigation wheel was turned or pressed: A short beep is issued.

• The output source was changed: A longer beep is issued when you select the OUTPUT

ON/OFF control (turn the output on or off).

To turn the beeper on or off from the front panel:

1. Press the MENU key, and then select BEEPER.

2. Select one of the following:

▪ ENABLE
▪ DISABLE

To turn the beeper on or off from the TSP command interface:

Set the beeper.enable attribute. For example, to enable the beeper, send:

beeper.enable = 1

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Display mode

Use the DISPLAY key to scroll through the various display modes shown in the figure below. Refer to

Display operations (on page 3-78) for more information about the display.

Figure 5: Display modes

Basic operation

Hazardous voltages may be present on all output and guard terminals. To prevent electrical
shock that could cause injury or death, never make or break connections to the Model 2651A
while the instrument is powered on. Turn off the equipment from the front panel or
disconnect the main power cord from the rear of the Model 2651A before handling cables.
Putting the equipment into standby does not guarantee that the outputs are powered off if a
hardware or software fault occurs.

Operation overview

From the front panel, you can configure the instrument to perform the following source-measure
operations:

• Source voltage: Measure and display current, voltage, resistance, or power

• Source current: Measure and display voltage, current, resistance, or power

• Measure resistance: Display resistance calculated from voltage and current components of

measurement (can optionally specify source voltage or source current value)

• Measure power: Display power calculated from voltage and current components of

measurement (can optionally specify source voltage or source current value)

• Measure only (V or I): Display voltage or current measurement

You can also configure source-measure operations using remote commands.

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Before you begin any of the following front-panel procedures, make sure that you exit out of the
menu structure. Press the EXIT (LOCAL) key as many times as needed to return to the
main display.

Voltage and current

The following table lists the source and measure limits for the voltage and current functions. The full
range of operation is explained in Operating boundaries (on page 4-5).

Model 2651A source-measure capabilities

Range

Source

Measure

100 mV

± 101 mV

± 102 mV

1 V

± 1.01 V

± 1.02 V

10 V

± 10.1 V

± 10.2 V

20 V

± 20.2 V

± 20.4 V

40 V

± 40.4 V

± 40.8 V

1 µA

± 1.01 µA

± 1.02 µA

10 µA

± 10.1 µA

± 10.2 µA

100 µA

± 101 µA

± 102 µA

1 mA

± 1.01 mA

± 1.02 mA

10 mA

± 10.1 mA

± 10.2 mA

100 mA

± 101 mA

± 102 mA

1 A

± 1.01 A

± 1.02 A

5 A

± 5.05 A

± 5.1 A

10 A

± 10.1 A

± 10.2 A

20 A

± 20.2 A

± 20.4 A

50 A

± 50.5 A

± 51 A

Maximum power = 202 W

Limits

When sourcing voltage, you can set the instrument to limit current or power. Conversely, when
sourcing current, you can set the instrument to limit voltage or power. In steady-state conditions, the
instrument output does not exceed the limit. The maximum limit is the same as the maximum values
listed in the following table.

The limit circuit limits in either polarity regardless of the polarity of the source or limit value. The
accuracy of the limit opposite in polarity from the source is diminished unless the instrument is in sink

mode (on page 2-23). The maximum limits are based on source range. For more information, see
Limit principles (on page 4-2).

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The limit operation of the instrument changes dependent on the source mode (current or voltage),
load, and the configured limits (current, voltage, and power). It is important to distinguish both the
current and voltage limits from the power limit. As the names imply, the current limit restricts the
current for sourced voltage, and the voltage limit restricts the voltage for a sourced current. The
power limit, however, restricts power by lowering the present limit in effect (voltage or current) as
needed to restrict the SMU from exceeding the specified power limit. For additional details on using
limits, including load considerations when specifying both a current (or a voltage) limit and a power
limit, see Operating boundaries (on page 4-5).

The only exception to the limit not being exceeded is the voltage limit when operating as a current
source. To avoid excessive and potentially destructive currents from flowing, the voltage limit
sources or sinks up to 160 mA for current source ranges on or below 100 mA. For the ranges 1 A
and 5 A, the maximum current is 5.4 A. For ranges 10 A and above, the maximum current allowed is
the current source setting.

Maximum limits for Model 2651A

Source range

Maximum limit

100 mV

20 A (50 A pulse)

1 V

20 A (50 A pulse)

10 V

20 A (50 A pulse)

20 V

10 A (50 A pulse)

40 V

5 A (50 A pulse)

100 nA

40 V

1 µA

40 V

10 µA

40 V

100 µA

40 V

1 mA

40 V

10 mA

40 V

100 mA

40 V

1 A

40 V

5 A

40 V

10 A

20 V

20 A

10 V

50 A (pulse)

40 V

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Setting the limit

Front-panel limit

Set the limit from the front panel as follows:

1. Press the LIMIT key to directly edit the limit value. Pressing the LIMIT key while in limit edit mode
will toggle the display between the complementary function limit and the power limit display.

2. Press the navigation wheel and set the limit to the new value.

3. Press the ENTER key or the navigation wheel to complete editing.

4. Press the EXIT (LOCAL) key to return to the normal display.

Setting the limit from a remote interface

The table below summarizes basic commands to program a limit. For a more complete description of
these commands, refer to the TSP command reference (on page 7-1).

Limit commands

Command

Description

smua.source.limiti = limit

Set current limit.

smua.source.limitv = limit

Set voltage limit.

smua.source.limitp = limit

Set power limit.

compliance = smua.source.compliance

Test if in limit (true = in limit; false = not in limit).

To set the limit, send the command with the limit value as the parameter. The following programming
example illustrates how to set the current, voltage, and power limit to 50 mA, 4 V, and 1 W,
respectively:

smua.source.limiti = 50e-3
smua.source.limitv = 4
smua.source.limitp = 1

The following programming example illustrates how to print the limit state:

print(smua.source.compliance)

A returned value of true indicates one of these things:

• If the instrument is configured as a current source, the voltage limit has been reached

• If the instrument is configured as a voltage source, the current limit has been reached

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Sink operation

Carefully consider and configure the appropriate output-off state, source function, and
compliance limits before connecting the Model 2651A to a device that can deliver energy (for
example, other voltage sources, batteries, capacitors, solar cells, or other Model 2651A
instruments). Configure recommended instrument settings before making connections to the
device. Failure to consider the output-off state, source, and compliance limits may result in
damage to the instrument or to the device under test (DUT).

When operating as a sink (V and I have opposite polarity), the SourceMeter instrument is dissipating
power rather than sourcing it. An external source (for example, a battery) or an energy storage device
(for example, a capacitor) can force operation into the sink region.

The accuracy of the limit opposite in polarity from the source is diminished unless the instrument is in
sink mode.

For example, if a 12 V battery is connected to the V-Source (HI to battery +) that is programmed for
+10 V, sink operation will occur in the second quadrant (source +V and measure -I).

When using the I-Source as a sink, always set the voltage compliance limit to levels that are
higher than the external voltage level. Failure to do so could result in excessive current flow
into the Model 2651A (<102 mA) and incorrect measurements.

The sink operating limits are shown in Continuous power operating boundaries (on page 4-6).

Sink mode

When operating as a sink, limit inaccuracies are introduced. Enabling sink mode reduces the source
limit inaccuracy seen when operating in quadrants II and IV. Quadrants I and III show this source limit
inaccuracy.

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Setting the sink mode using the front panel

To enable or disable the sink mode from the front panel:

1. Press the CONFIG key and then the SRC key.

2. Select V-SOURCE.

3. Select SINK-MODE.

4. Select ENABLE or DISABLE.

5. Press the ENTER key. Sink mode is enabled or disabled, as applicable.

6. Press the EXIT (LOCAL) key twice to return to the main display.

Setting the sink mode from a remote interface

To enable sink mode from the remote interface, send:

smua.source.sink = smua.ENABLE

To disable sink mode, send:

smua.source.sink = smua.DISABLE

Fundamental circuit configurations

The fundamental source-measure configurations for the Model 2651A are shown in the following
figures. When sourcing voltage, you can measure current or voltage, as shown in the following figure.

Figure 6: Fundamental source-measure configurations: Source V

A

Current meter

+ − Voltage source
V

Voltage meter

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When sourcing current, you can measure voltage or current, as shown in the following figure.

Figure 7: Fundamental source-measure configuration: Source I

A

Current meter

↑

Current source

V

Voltage meter

See Basic circuit configurations (on page 4-20) for detailed information.

Operation considerations for the ADC

The following paragraphs discuss autozero and NPLC caching with the analog-to-digital converter

(ADC) (on page 4-1). Autozero and NPLC caching only apply to the integrating ADC. They are not

used with the fast (high-speed) ADC.

Autozero

The ADC of the Model 2651A uses a ratiometric analog to digital (A/D) conversion technique. To
ensure reading accuracy, the instrument must periodically obtain fresh measurements of its internal
ground and voltage reference. Separate reference and zero measurements are used for each
aperture.

As summarized in the table below, there are different settings for autozero. By default, the instrument
is set to AUTO, which automatically checks these reference measurements whenever a signal
measurement is made. If the reference measurements are out of date when a signal measurement is
made, the instrument automatically makes two more A/D conversions, one for the reference and one
for the zero, before returning the result. Thus, occasionally, a measurement takes longer than normal.

This extra time can cause problems in sweeps and other test sequences in which measurement
timing is critical. To avoid the extra time for the reference measurements in these situations, you can
select OFF. This setting disables the automatic reference measurements. Note that with automatic
reference measurements disabled, the instrument may gradually drift out of specification.

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To minimize the drift, make a reference and zero measurement immediately before a critical test
sequence. You can use the ONCE setting to force a refresh of the reference and zero measurements
used for the current aperture setting.

Autozero settings

Autozero setting

Description

OFF

Turns automatic reference measurements off.

ONCE

After immediately making one reference and one zero measurement, turns automatic
reference measurements off.

AUTO

Automatically makes new acquisitions when the Model 2651A determines reference and
zero values are out-of-date.

Setting autozero from the front panel

To change autozero from the front panel:

1. Press the CONFIG key.

2. Press the MEAS key.

3. Turn the navigation wheel to select AUTO-ZERO, and then press the ENTER key or the
navigation wheel.

4. Turn the navigation wheel to select the mode (OFF, ONCE, or AUTO), and then press the
ENTER key or the navigation wheel.

5. Press the EXIT (LOCAL) key to return to the previous display.

Setting autozero from a remote interface

To set autozero from a remote interface:

Use the autozero command with the appropriate option shown in the following table to set autozero
through a remote interface (see smuX.measure.autozero (on page 7-245)). For example, send the
following command to activate automatic reference measurements:

smua.measure.autozero = smua.AUTOZERO_AUTO

Autozero command and options

Command

Description

smua.measure.autozero = smua.AUTOZERO_OFF

Disable autozero (old NPLC cache values are
used when autozero is disabled (see NPLC

caching (on page 2-27)).

smua.measure.autozero = smua.AUTOZERO_ONCE

After immediately taking one reference and one
zero measurement, turns automatic reference
measurements off.

smua.measure.autozero = smua.AUTOZERO_AUTO

Automatically takes new acquisitions when the
Model 2651A determines reference and zero
values are out-of-date.

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NPLC caching

NPLC caching speeds up operation by caching A/D reference and zero values for up to the ten most
recent measurement aperture settings. Whenever the integration rate is changed using the SPEED
key, or a user setup is recalled, the NPLC cache is checked. If the integration rate is already stored in
the cache, the stored reference and zero values are recalled and used. If the integration rate is not
already stored in the cache, a reference and zero value is acquired and stored in the cache when the
next measurement is made. If there are already ten NPLC values stored, the oldest one is overwritten
by the newest one. When autozero is off, NPLC values stored in the cache are used,
regardless of age.

Basic source-measure procedure

Front-panel source-measure procedure

Use the following procedure to perform the basic source-measure operations of the Model 2651A
SMU using the front panel. The following procedure assumes that the Model 2651A is already
connected to the device under test (DUT), as explained in DUT test connections (on page 2-45).

Hazardous voltages may be present on all output and guard terminals. To prevent electrical
shock that could cause injury or death, never make or break connections to the Model 2651A
while the instrument is powered on. Turn off the equipment from the front panel or
disconnect the main power cord from the rear of the Model 2651A before handling cables.
Putting the equipment into standby does not guarantee that the outputs are powered off if a
hardware or software fault occurs.

Step 1: Select and set the source level

To select the source and edit the source value:

1. Press the SRC key as needed to select the voltage source or current source, as indicated by the
units in the source field on the display. The flashing digit (cursor) indicates which value is
presently selected for editing.

2. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode.

3. Use the RANGE keys to select a range that accommodates the value you want to set. For best
accuracy, use the lowest possible source range.

4. Enter the source value.

5. Press the ENTER key or the navigation wheel to complete editing.

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Step 2: Set the compliance limit

Perform the following steps to edit the compliance limit value:

1. Press the LIMIT key.

2. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode,
as indicated by the EDIT indicator.

3. Enter the limit value, then press the ENTER key or the navigation wheel to complete editing.

Step 3: Select the measurement function and range

Select measurement function and range as follows:

1. Select the measurement function by pressing the MEAS key.

2. Set the measurement range with the RANGE keys, or enable AUTO range. When setting the
range, consider the following points:

▪ When measuring the source (such as when sourcing V and measuring V), you cannot select

the measurement range using the RANGE keys. The selected source range determines the
measurement range.

▪ When not measuring the source (such as when sourcing V but measuring I), you can select

the measurement range selection manually or the instrument can set it automatically. When
using manual ranging, use the lowest possible range for best accuracy. When autorange is
enabled, the Model 2651A automatically goes to the most sensitive range to make
the measurement.

Step 4: Turn the output on

Turn on the output by pressing the OUTPUT ON/OFF switch. The OUTPUT indicator light turns on.

Step 5: Observe readings on the display.

Press the TRIG key if necessary to trigger the instrument to begin making readings. The readings are
on the top line, and source and limit values are on the bottom line.

Step 6: Turn the output off

When finished, turn the output off by pressing the OUTPUT ON/OFF switch. The OUTPUT indicator
light turns off.

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Remote source-measure commands

Basic source-measurement procedures can also be performed through a remote interface. To do this,
send the appropriate commands. The following table summarizes basic source-measure commands.
See Introduction to TSP operation (on page 5-1) for more information on using these commands.

Basic source-measure commands

Command

Description

smua.measure.autorangei = smua.AUTORANGE_ON

Enable current measure autorange.

smua.measure.autorangev = smua.AUTORANGE_ON

Enable voltage measure autorange.

smua.measure.autorangei = smua.AUTORANGE_OFF

Disable current measure autorange.

smua.measure.autorangev = smua.AUTORANGE_OFF

Disable voltage measure autorange.

smua.measure.rangei = rangeval

Set current measure range.

smua.measure.rangev = rangeval

Set voltage measure range.

reading = smua.measure.i()

Request a current reading.

reading = smua.measure.v()

Request a voltage reading.

iReading, vReading = smua.measure.iv()

Request a current and voltage reading.

reading = smua.measure.r()

Request a resistance reading.

reading = smua.measure.p()

Request a power reading.

smua.source.autorangei = smua.AUTORANGE_ON

Enable current source autorange.

smua.source.autorangev = smua.AUTORANGE_ON

Enable voltage source autorange.

smua.source.autorangei = smua.AUTORANGE_OFF

Disable current source autorange.

smua.source.autorangev = smua.AUTORANGE_OFF

Disable voltage source autorange.

smua.source.func = smua.OUTPUT_DCVOLTS

Select voltage source function.

smua.source.func = smua.OUTPUT_DCAMPS

Select current source function.

smua.source.leveli = sourceval

Set current source value.

smua.source.levelv = sourceval

Set voltage source value.

smua.source.limiti = level

Set current limit.

smua.source.limitv = level

Set voltage limit.

smua.source.limitp = level

Set power limit.

smua.source.output = smua.OUTPUT_ON

Turn on source output.

smua.source.output = smua.OUTPUT_OFF

Turn off source output.

smua.source.rangei = rangeval

Set current source range.

smua.source.rangev = rangeval

Set voltage source range.

smua.sense = smua.SENSE_LOCAL

Select local sense (2-wire).

smua.sense = smua.SENSE_REMOTE

Select remote sense (4-wire).

Requesting readings

You can request readings by including the appropriate measurement command as the argument for
the print() command. The following programming example illustrates how to request a current

reading:

print(smua.measure.i())

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Source-measure programming example

The following SMU programming example illustrates the setup and command sequence of a basic
source-measure procedure with the following parameters:

• Source function and range: Voltage, autorange

• Source output level: 5 V

• Current compliance limit: 10 mA

• Measure function and range: Current, 10 mA

-- Restore Model 2651A defaults.

smua.reset()

-- Select voltage source function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Set source range to autorange.

smua.source.autorangev = smua.AUTORANGE_ON

-- Set voltage source to 5 V.

smua.source.levelv = 5

-- Set current limit to 10 mA.

smua.source.limiti = 10e-3

-- Set current range to 10 mA.

smua.measure.rangei = 10e-3

-- Turn on output.

smua.source.output = smua.OUTPUT_ON

-- Print and place the current reading in the reading buffer.

print(smua.measure.i(smua.nvbuffer1))

-- Turn off output.

smua.source.output = smua.OUTPUT_OFF

Triggering in local mode

You do not need to change any trigger settings to use the basic source and measurement procedures
described in the following topics.

Press the MENU key, and then select SETUP > RECALL > INTERNAL > FACTORY to reset the
factory default conditions.

The following figure shows the general sequence for SMU measurement triggering. The basic
sequence is as follows:

• When the output is turned on, the programmed source value is immediately applied to the device

under test (DUT).

• Through front panel only: If the immediate trigger source is selected, a measurement is triggered

immediately. However, if the manual trigger source is selected, the front-panel TRIG key must be
pressed.

• The instrument waits for the programmed delay period (if any).

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• The instrument makes one measurement.

• If the number of measurements is less than the programmed trigger count, it cycles to make

another measurement (the measurement cycle is repeated indefinitely if the infinite trigger count
is selected).

• For multiple measurements, the instrument waits for the programmed trigger interval (if any)

before making the next measurement.

Figure 8: Local triggering

Configuring trigger attributes in local mode

From the front panel, press the CONFIG key, and then select TRIG. The following menu items are
available:

• TRIGGER-IN: Use these options to select the trigger-in source:

▪ IMMEDIATE: Triggering occurs immediately and the instrument starts to make

measurements when it is ready (for example, after the source output is turned on).

▪ MANUAL: The front-panel TRIG key must be pressed to trigger the instrument to

make readings.

• COUNT: Sets the trigger count (number of measurements) as follows:

▪ FINITE: The instrument goes through measurement cycles for the programmed trigger count

(1 to 99999).

▪ INFINITE: The instrument goes through measurement cycles indefinitely until halted.

• INTERVAL: Sets the time interval between measurements (0 s to 999.999 s) when the count is

greater than 1.

• DELAY: Sets the delay period between the trigger and the start of measurement

(0 s to 999.999 s).

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Front-panel triggering example

This example configures the trigger parameters to meet the following requirements:

• Manual triggering (TRIG key)

• Infinite trigger count (cycle indefinitely through measurement cycles)

• Interval (time between measurements): 1 s

• Delay (time from trigger to measurement): 2 s

To configure the trigger parameters:

1. Press the CONFIG key, and then the TRIG key.

2. Select TRIGGER-IN, and then press the ENTER key or the navigation wheel.

3. Select MANUAL, and then press the ENTER key or the navigation wheel.

4. Select COUNT, then select INFINITE, and then press the ENTER key or the navigation wheel.

5. Select INTERVAL, set the interval to 1 s, and then press the ENTER key or the navigation wheel.

6. Choose DELAY, set the delay to 2 s, and then press the ENTER key.

7. Press EXIT (LOCAL) to return to the main display.

8. Press the OUTPUT ON/OFF control to turn the output on.

9. Press TRIG. A 2 s delay occurs before the first measurement. The instrument cycles through
measurements indefinitely with a 1 s interval between measurements.

10. Press the OUTPUT ON/OFF control again to stop taking readings.

Configuring for measure-only tests using the MODE key

In addition to using the Model 2651A for conventional source-measure operations, you can also use it
like a meter to measure current, voltage, resistance, or power.

To configure the Model 2651A as a voltage meter, current meter, ohmmeter, or wattmeter:

1. Press the MODE key.

2. Turn the navigation wheel to select the type of meter from the menu (I-METER, V-METER,
OHM-METER, or WATT-METER).

3. Press the ENTER key to complete the configuration of the Model 2651A as the selected meter.

To manually configure the settings, refer to the following topics:

• Voltmeter and ammeter measurements (on page 2-33)

• Ohms measurements (on page 2-34)

• Power measurements (on page 2-37)

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Voltmeter and ammeter measurements

You can make voltmeter and ammeter measurements without using the MODE key, such as when
configuring measure-only tests over the remote interface.

To use the Model 2651A to measure voltage or current:

1. Select the source-measure functions:
▪ Voltmeter: Press the SRC key to select the current source and press the MEAS key to select

the voltage measurement function.

▪ Ammeter: Press the SRC key to select the voltage source and press the MEAS key to select

the current measurement function.

2. Set source and compliance levels. To edit the source level, use the procedure provided in Step 1:

Select and set the source level (on page 2-27); to edit the compliance level, use the procedure

provided in Step 2: Set the compliance limit (on page 2-28):

▪ Select the lowest source range and set the source level to zero.
▪ Set the compliance level to a value that is higher than the expected measurement.

When using the Model 2651A as a voltmeter, the voltage compliance limit must be set higher
than the voltage that is being measured. Failure to do this could result in excessive current
flow into the Model 2651A (<100 A), incorrect measurements, and possible damage to the
instrument.

3. Use the RANGE keys to select a fixed measurement range that accommodates the expected
reading. Use the lowest possible range for best accuracy. You can also select autorange, which
automatically sets the Model 2651A to the most sensitive range.

4. Connect the voltage or current to be measured. Make sure to use 2-wire connections from the
Model 2651A to the device under test (DUT) (see DUT test connections (on page 2-45)).

5. Press the OUTPUT ON/OFF control to turn the output on.

6. View the displayed reading (press the TRIG key if necessary).

7. When finished, press the OUTPUT ON/OFF control to turn the output off.

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2-34 2651A-901-01 Rev. C October 2021

Ohms measurements

Resistance readings are calculated from the measured current and measured voltage as follows:
R = V/I
Where:

• R is the calculated resistance

• V is the measured voltage

• I is the measured current

Ohms ranging

The front-panel ohms function does not use ranging. The instrument formats a calculated resistance
reading (V/I) to best fit the display. There may be leading zeros if the ohms reading is less than 1 mΩ.

Basic ohms measurement procedure

When you use the MODE key to select ohms measurement, the Model 2651A is automatically
configured as a current source with a level of 1 mA. If you wish to change the source function, source
value, or compliance value (in other words, if you wish to customize the MODE key's standard
ohm-meter's configuration), then perform the following steps to perform ohms measurements. The
following procedure assumes that the Model 2651A is already connected to the device under test
(see DUT test connections (on page 2-45)).

To take an ohms measurement:

1. Press the SRC key to select the source function.

2. Set the output source (current or voltage, dependent on which function is selected) to a value
based on the expected resistance. See Step 1: Select and set the source level (on page 2-27)
earlier in this section.

3. Press the LIMIT key to edit the voltage or current limit. When programming a voltage limit, set the
voltage limit above the maximum expected voltage across the resistor under test. When
programming a current limit, set the current limit at or above the maximum expected current
through the resistor under test. See Step 2: Set the compliance limit earlier in this section.

4. Press the MEAS key to display voltage or current.

5. Make sure that AUTO measurement range is on (press the AUTO key if needed).

6. Press the MEAS key as many times as needed to display ohms.

7. Press the OUTPUT ON/OFF control to turn the output on.

8. View the displayed reading (press the TRIG key if necessary). When finished, press the OUTPUT
ON/OFF control again to turn the output off.

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2651A-901-01 Rev. C October 2021 2-35

Remote ohms command

Use the smua.measure.r() function to get a resistance reading.
The programming example below illustrates how to get a resistance reading:

reading = smua.measure.r()

See Remote source-measure commands (on page 2-29) for more commands to set up source and
measure functions, and Introduction to TSP operation (on page 5-1) for more details.

Ohms programming example

The following programming example illustrates the setup and command sequence of a typical ohms
measurement procedure with the following parameters:

• Source function: current, 10 mA range, 10 mA output

• Voltage measure range: auto

• Voltage compliance: 10 V

• Sense mode: 4-wire

-- Restore Model 2651A defaults.

smua.reset()

-- Select current source function.

smua.source.func = smua.OUTPUT_DCAMPS

-- Set source range to 10 mA.

smua.source.rangei = 10e-3

-- Set current source to 10 mA.

smua.source.leveli = 10e-3

-- Set voltage limit to 10 V.

smua.source.limitv = 10

-- Enable 4-wire ohms.

smua.sense = smua.SENSE_REMOTE

-- Set voltage range to auto.

smua.measure.autorangev = smua.AUTORANGE_ON

-- Turn on output.

smua.source.output = smua.OUTPUT_ON

-- Get resistance reading.

print(smua.measure.r())

-- Turn off output.

smua.source.output = smua.OUTPUT_OFF

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Ohms sensing

Ohms measurements can be made using either 2-wire or 4-wire sensing. See DUT test connections
(on page 2-45) for information on connections and sensing methods.

The 2-wire sensing method has the advantage of requiring only two test leads. However, as shown in
the following figure (2-wire resistance sensing), test lead resistance can seriously affect the accuracy
of 2-wire resistance measurements, particularly with lower resistance values.

Figure 9: Two-wire resistance sensing

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The 4-wire sensing method, as shown in the following figure (4-wire resistance sensing), minimizes or
eliminates the effects of lead resistance by measuring the voltage across the resistor under test with a
second set of test leads. Because of the high input impedance of the voltmeter, the current through
the sense leads is negligible, and the measured voltage is essentially the same as the voltage across
the resistor under test.

Figure 10: Four-wire resistance sensing

Power measurements

Power readings are calculated from the measured current and voltage as follows:

Where:
P is the calculated power
V is the measured voltage
I is the measured current

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Basic power measurement procedure

If you need to customize the standard wattmeter configuration of the MODE key, perform the
following steps to make power measurements. The following procedure assumes that the Model
2651A is already connected to the device under test (DUT) as explained in DUT test connections (on
page 2-45).

Hazardous voltages may be present on all output and guard terminals. To prevent electrical
shock that could cause injury or death, never make or break connections to the Model 2651A
while the output is on. Turn off the equipment from the front panel or disconnect the main
power cord from the rear of the Model 2651A before handling cables. Putting the equipment
into an output-off state does not guarantee that the outputs are powered off if a hardware or
software fault occurs.

To perform power measurements from the front panel:

1. Set source function and value. Press the SRC key to select the voltage or current source function,
as required.

2. Set the output voltage or current to an appropriate value.

3. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode.

4. Use the RANGE keys to select a range that accommodates the value you want to set. For best
accuracy, use the lowest possible source range.

5. Enter the source value.

6. Press the ENTER key or the navigation wheel to complete editing.

7. Press the LIMIT key and set the voltage or current limit high enough for the expected voltage or
current across the DUT to be measured.

8. Press the LIMIT key.

9. Move the cursor to the digit to change, then press the navigation wheel to enter the EDIT mode,
as indicated by the EDIT indicator.

10. Enter the limit value, then press the ENTER key or the navigation wheel to complete editing.

11. Press the MEAS key as many times as needed to display power.

12. Press the OUTPUT ON/OFF control to turn the output on.

13. View the displayed reading (press the TRIG key if necessary).

14. When finished, press the OUTPUT ON/OFF control again to turn the output off.

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2651A-901-01 Rev. C October 2021 2-39

Power measurements using the remote interface

The following paragraphs summarize basic power measurement commands using the remote
interface and also give a programming example for a typical power measurement situation.

Remote power reading command

The programming example below illustrates how to get a power reading:

reading = smua.measure.p()

See Remote source-measure commands (on page 2-29) for more commands necessary to set up
source and measure functions and also Introduction to TSP operation (on page 5-1).

Power measurement programming example

The following programming example illustrates the setup and command sequence for a typical power
measurement procedure with the following parameters:

• Source function: Voltage, source autorange, 5 V output

• Current measure function and range: Current, autorange

• Current compliance: 50 mA

-- Restore Model 2651A defaults.

smua.reset()

-- Select voltage source function.

smua.source.func = smua.OUTPUT_DCVOLTS

-- Enable source autoranging.

smua.source.autorangev = smua.AUTORANGE_ON

-- Set voltage source to 5 V.

smua.source.levelv = 5

-- Set current limit to 50 mA.

smua.source.limiti = 50e-3

-- Set current range to autorange.

smua.measure.autorangei = smua.AUTORANGE_ON

-- Turn on the output.

smua.source.output = smua.OUTPUT_ON

-- Retrieve a power reading.

print(smua.measure.p())

-- Turn off the output.

smua.source.output = smua.OUTPUT_OFF

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Contact check measurements

The contact check function prevents measurements that may be in error due to excessive resistance
in the force or sense leads when making remotely sensed (Kelvin) measurements (see 4-wire remote

sensing connections (on page 2-47) for more detail). Potential sources for this resistance include poor

contact at the device under test (DUT), failing relay contacts on a switching card, and wires that are
too long or thin. To use contact check, the current limit must be at least 1 mA (this allows enough
current to flow when performing the test), and the source-measure unit (SMU) must not be in High-Z
output-off mode.

The contact check function will also detect an open circuit that may occur when a four-point probe is
misplaced or misaligned. This relationship is shown schematically in the figure titled "Contact check
measurements," where RC is the resistance of the mechanical contact at the DUT, and RS is the
series resistance of relays and cables,.

Figure 11: Contact check

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Contact check commands

The following table summarizes the basic contact check commands. For complete descriptions of
these commands, refer to the TSP command reference (on page 7-1). For connection information,
refer to Contact check connections (on page 2-49).

Basic contact check commands

Command*

Description

flag = smua.contact.check()

Determine if the contact resistance is lower than
the threshold.

rhi, rlo = smua.contact.r()

Measure the aggregate contact resistance.

smua.contact.speed = speed_opt

Set speed_opt to one of the following:

▪ 0 or smua.CONTACT_FAST
▪ 1 or smua.CONTACT_MEDIUM
▪ 2 or smua.CONTACT_SLOW

smua.contact.threshold = rvalue

Set the resistance threshold for the contact check
function.

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Contact check programming example

The following programming example illustrates the setup and command sequence for a typical
contact check measurement. These commands set the contact check speed to fast and the threshold
to 100 Ω. Then, a contact check measurement against the threshold is made. If it fails, a more
accurate contact check measurement is made, and the test is aborted. Otherwise, the output is
turned on, and the test continues.

-- Restore defaults.

smua.reset()

-- Set contact check speed to fast.

smua.contact.speed = smua.CONTACT_FAST

-- Set the contact check threshold to 100 ohms.

smua.contact.threshold = 100

-- Check contacts against threshold.

if not smua.contact.check() then

-- Set speed to slow.

smua.contact.speed = smua.CONTACT_SLOW

-- Get aggregate resistance readings.

rhi, rlo = smua.contact.r()

-- Return contact resistances to the host.

print(rhi, rlo)

-- Terminate execution.

exit()
end

-- Turn output on and continue.

smua.source.output = smua.OUTPUT_ON

Saved setups

You can restore the Model 2651A to one of six nonvolatile-memory setup configurations (five user
setups and one factory default), or to a setup stored on an external USB flash drive. As shipped from
the factory, the Model 2651A powers up with the factory default settings, which cannot be overwritten.
The default settings are also in the five user setup locations, but may be overwritten. The factory
default settings are listed in the command descriptions in the TSP command reference (on page 7-1).

You can also change the setup configuration that is used when the instrument powers up.

Saving user setups

You can save the present Model 2651A setup to internal nonvolatile memory or a USB flash drive.

To save a user setup to nonvolatile memory from the front panel:

1. Configure the Model 2651A to the settings that you want to save.

2. Press the MENU key.

3. Select SETUP and then press the ENTER key.

4. Select the SAVE menu item and then press the ENTER key.

5. Select INTERNAL and then press the ENTER key.

6. Select the user number (1 through 5) and press the ENTER key.

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To save a user setup to an external USB flash drive from the front panel:

1. Configure the Model 2651A to the settings that you want to save.

2. Insert the USB flash drive into the USB port on the front panel of the Model 2651A.

3. Press the MENU key.

4. Select SETUP and then press the ENTER key.

5. Select SAVE and then press the ENTER key.

6. Select USB1. The file name setup000.set is displayed.

7. Turn the navigation wheel to change the last three digits of the file name and then press the
ENTER key.

To save and recall user setups using remote commands:

Use the setup.save() and setup.recall() functions to save and recall user setups. The
following example saves the present setup as setup 1, and then recalls setup 1.

-- Save the present setup to nonvolatile memory.

setup.save(1)

-- Recall the saved user setup from nonvolatile memory.

setup.recall(1)

Recalling a saved setup using the front panel

You can recall setups from internal nonvolatile memory or a USB flash drive.

To recall a saved setup from the front panel:

1. Press the MENU key to access the main menu.

2. Select SETUP, and then press the ENTER key.

3. Select the RECALL menu item, and then press the ENTER key.

4. Select one of the following:

▪ INTERNAL
▪ USB1

5. INTERNAL only: Do one of the following:

▪ Select the user number (1 through 5), then press the ENTER key.
▪ Select FACTORY to restore factory defaults, then press the ENTER key.

6. USB1 only: Select the appropriate file and then press the ENTER key.

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Start-up configuration

You can specify the Model 2651A start-up (power-on) configuration from the front panel. Set the
start-up configuration to a previously stored setup (recalled from internal nonvolatile memory) or reset
to the factory default setup.

To select the power-on setup:

1. Press the MENU key to access the main menu.

2. Select SETUP, and then press the ENTER key.

3. Select POWERON, and then press the ENTER key.

4. Select the configuration to use.

5. Press the ENTER key.

6. To return to the previous menu or display, press the EXIT (LOCAL) key.

To select the power-on setup using remote commands:

Use the setup.poweron attribute to select which setup to use when the instrument power up. To set
the setup.poweron configuration attribute:

setup.poweron = n

Where n is:

• 0 (*RST or reset() factory defaults)

• 1 to 5 (user setup 1 to 5)

Restoring the factory default setups using remote commands

Use one of the reset functions to return the Model 2651A to the original factory defaults. An example
of each type of reset is shown in the following program examples.

Restore all factory defaults of all nodes on the TSP-Link® network:

reset()

Restore all factory defaults (note that you cannot use *rst in a script):

*rst

Restore all factory defaults:

setup.recall(0)

Restore channel A defaults:

smua.reset()

Reset only the local TSP-Link node:

localnode.reset()

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DUT test connections

On some sensitive or easily damaged devices under test (DUTs), the instrument power-up and
power-down sequence can apply transient signals to the DUT that may affect or damage it. When
testing this type of DUT, do not make final connections to it until the instrument has completed its
power-up sequence and is in a known operating state. When testing this type of DUT, disconnect it
from the instrument before turning the instrument off.

To prevent any human contact with a live conductor, connections to the DUT must be fully insulated
and the final connections to the DUT must only use safety-rated safety-jack-socket connectors that
do not allow bodily contact.

Input/output connectors

The Keithley Instruments Model 2651A High Power System SourceMeter® Instrument uses screw
terminal connectors for input and output connections to devices under test (DUTs).

A screw terminal connector can be removed from the rear panel by loosening the two captive
retaining screws and pulling it off the rear panel. Each screw in the terminal connector cable
assembly (used with the terminal connector) can accommodate from 24 AWG (0.2 mm2) to 12 AWG
(2.5 mm2) conductors. The screws in the output connector cable assembly (used with the output
connector) requires use of 6 AWG (16 mm2) conductors.

Basic connection sequence:

1. With the output off and the connector uninstalled from the Model 2651A rear panel, make the wire
connections from a connector to the DUT.

2. Reinstall the connector onto the rear panel.

3. If using a screw terminal connector, tighten the two captive screws.

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Hazardous voltages may be present on the output and guard terminals. To prevent electrical
shock that could cause injury or death, never make or break connections to the Model 2651A
while the output is on. Power off the equipment from the front panel or disconnect the main
power cord from the rear of a Model 2651A before handling cables connected to the outputs.
Putting the equipment into standby does not guarantee the outputs are not powered if a
hardware or software fault occurs.

Maximum floating (common mode) voltage for a SMU is 250 V. Exceeding this level could
damage the instrument and create a shock hazard. See Floating a SMU (on page 2-63) later in
this section for details on floating the SMUs.

The input/output connectors of the High Power System SourceMeter® Instrument are rated for
connection to circuits rated Installation Category I only, with transients rated less than 1500 V
peak. Do not connect the Model 2651A terminals to CAT II, CAT III, or CAT IV circuits.
Connections of the input/output connectors to circuits higher than CAT I can cause damage
to the equipment or expose the operator to hazardous voltages.

To prevent electric shock and/or damage to the High Power System SourceMeter® Instrument,
when connecting to a source with a greater current capability than the Model 2651A, a
user-supplied fuse, rated at no more than 20 A SLO-BLO, should be installed in-line with the
Model 2651A input/output connectors.

Figure 12: Model 2651A input/output connectors

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2651A-901-01 Rev. C October 2021 2-47

Input/output LO and chassis ground

Connections to LO on the Model 2651A are not necessarily at 0 V. Hazardous voltages could
exist between LO and chassis ground. Make sure that high-voltage precautions are taken
throughout the test system. Alternatively, limit hazardous levels by adding external
protection to limit the voltage between LO and chassis. Failure to make sure high-voltage
precautions are used throughout the test system or a failure to limit hazardous levels could
result in severe personal injury or death from electric shock. SMU input/output LO is available
at the rear panel terminal block (labeled OUTPUT). Input/output LO is electrically isolated
from chassis ground. See Rear panel (on page 2-6) for location of chassis ground connection.

Using the chassis as a ground point for signal connections to the Model 2651A chassis may result in
higher or lower noise. The tie point to the chassis can help quiet measurements if the Model 2651A
common-mode current is channeled to the chassis instead of the device. However, if other
equipment is also connected to the chassis, higher noise (due to the other connected equipment)
may result when using the chassis as a ground point. If you choose to use the chassis as a ground
point for signal connections, use the Model 2651A chassis screw as a connection point.

2-wire local sensing connections

You can use 2-wire local sensing measurements, shown in the following figure, for the following
source-measure conditions:

• Sourcing and measuring current.

• Sourcing and measuring voltage in high impedance (more than 1 kΩ) test circuits.

When using 2-wire local sensing connections, make sure to properly configure the Model 2651A

Sense mode selection (on page 2-64).

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

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Figure 13: Two-wire resistance connections

4-wire remote sensing connections

By default, the Model 2651A instruments are configured to use 2-wire (local) voltage sensing. If you
choose to enable 4-wire (remote) voltage sensing, it is critical that you establish and maintain the
proper Kelvin connections between the corresponding force and sense leads to ensure the proper
operation of the instrument and to make accurate voltage measurements. Sense HI must be
connected to Force HI, and Sense LO must be connected to Force LO.

When sourcing voltage with remote sense, the instrument relies on the voltage detected with the
sense lines to provide the proper closed-loop control of its output voltage and to properly limit the
voltage across the device-under-test. If a sense line becomes disconnected from its corresponding
force line, an erroneous voltage is sensed. The output voltage may be adjusted to a level that is
radically different than the programmed voltage level (possibly to hazardous levels). In addition, the
voltage across the device may exceed the programmed source limit voltage, possibly causing
damage to the device or test fixture.

In both cases, the voltage is not measured correctly if a sense lead becomes disconnected from its
corresponding force lead.

You can use contact check to verify that the sense leads are connected. Refer to Contact check

measurements (on page 2-40) for more information.

You can use 4-wire remote sensing at any time, however, it is strongly recommended for the following
source-measure conditions:

• Sourcing or measuring voltage in low impedance (less than 1 kΩ) test circuits.

• Enforcing voltage compliance limit directly at the DUT.

When using 4-wire local sensing connections, make sure to properly configure the Model 2651A

Sense mode selection (on page 2-64).

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When sourcing or measuring voltage in a low-impedance test circuit (see the figure below), there can
be errors associated with lead resistance. Voltage source and measure accuracy are optimized by
using 4-wire remote sense connections. When sourcing voltage, 4-wire remote sensing ensures that
the programmed voltage is delivered to the device under test (DUT). When measuring voltage, only
the voltage drop across the DUT is measured.

Figure 14: Model 2651A four-wire connections (remote sensing)

You may need additional connections for redundant protective earth (safety ground) that are not
shown in the preceding graphic.

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

Contact check connections

The contact check function prevents measurement errors due to excessive resistance in the source or
sense leads. See Contact check measurements (on page 2-40) for operation.

Contact check requires both source and sense connections. Refer to 4-wire remote sensing

connections (on page 2-47) for the connection scheme.

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Multiple SMU connections

Connections to LO on the Model 2651A are not necessarily at 0 V. Hazardous voltages could
exist between LO and chassis ground. Make sure that high-voltage precautions are taken
throughout the test system. Alternatively, limit hazardous levels by adding external
protection to limit the voltage between LO and chassis. Failure to make sure high-voltage
precautions are used throughout the test system or a failure to limit hazardous levels could
result in severe personal injury or death from electric shock.

Carefully consider and configure the appropriate output-off state, source function, and
compliance limits before connecting the Model 2651A to a device that can deliver energy (for
example, other voltage sources, batteries, capacitors, solar cells, or other Model 2651A
instruments). Configure recommended instrument settings before making connections to the
device. Failure to consider the output-off state, source, and compliance limits may result in
damage to the instrument or to the device under test (DUT).

The following figure shows how to use the SMUs of two Model 2651A instruments to test a 3-terminal
device, such as an N-channel JFET (see TSP advanced features (on page 6-61) for information on
using multiple Model 2651A instruments). A typical application is for the Model 263xB to source a
range of gate voltages, while the Model 2651A sources voltage to the drain of the device and
measures current at each gate voltage.

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

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Figure 15: Two SMUs connected to a 3-terminal device (local sensing)

The outputs of multiple SMUs can also be combined to obtain higher current and voltage levels (pulse
only operation). For information including instrument configuration considerations and cautions, refer
to Combining SMU outputs (on page 2-51).

Combining SMU outputs

The following information provides cautions and important considerations that need to be observed
when combining SMU output channels.

Use care when combining SMU channels. Whenever SMU channels are combined, it is best to use
instruments with identical current and voltage envelopes and ranges.

Carefully consider and configure the appropriate output-off state, source function, and
compliance limits before connecting the Model 2651A to a device that can deliver energy (for
example, other voltage sources, batteries, capacitors, solar cells, or other Model 2651A
instruments). Configure recommended instrument settings before making connections to the
device. Failure to consider the output-off state, source, and compliance limits may result in
damage to the instrument or to the device under test (DUT).

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Pulse characteristics of the Model 2651A

When combining the outputs of two Model 2651A High Power System SourceMeter® Instruments,
restrict operation to pulse only for all operating areas (both the standard and the extended operating
areas). The following figure and table illustrate the pulse regions for each SMU when used in
combination with another SMU. Refer to the Model 2651A specifications on tek.com/keithley for the
latest pulse width and duty cycle information. Measurements are given priority over source and
display operations, so make sure that the measurement time does not exceed the allowable pulse
width and duty cycle in a particular pulse region.

Figure 16: SMU pulse regions when combining SMUs

Pulse region specification

Region (quadrant diagram)

Region maximum

Maximum pulse width

Maximum duty cycle

2

30 A at 10 V

1 ms

50%

3

20 A at 20 V

1.5 ms

40%

4

10 A at 40 V

1.5 ms

40%

5

50 A at 10 V

1 ms

35%

6

50 A at 20 V

330 µs

10%

7

50 A at 40 V

300 µs

1%

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Configuration guidelines

Configuration guidelines are presented in the following table. Additional information, including
examples on combining SMU channels, can be found in application notes on tek.com/keithley.
Application notes include "Testing to 100A by Combining Keithley Model 2651A High Power
SourceMeter Instruments."

SourceMeter instrument configuration

Guidelines

Source current using parallel SMUs

Maximum Pulsed Signal Levels for Model 2651A:

100 A with 36 V compliance

SMU 1 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Current limit for normal output-off mode (this is the maximum current
that will flow between the two SMUs when the output is off):
smuX.source.offlimiti = 1e-3 (default)
Voltage compliance must be 10% lower than the voltage compliance
of SMU 2. Therefore, this SMU will control the maximum voltage
across the DUT. Voltage compliance limit (maximum):
smuX.trigger.source.limitv = 36

SMU 2 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCAMPS
Normal output-off voltage limit:
smuX.source.offlimitv = 40 (default)
Voltage compliance must be 10% higher than the voltage compliance
of SMU 1. Voltage compliance limit (maximum):
smuX.trigger.source.limitv = 40

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SourceMeter instrument configuration

Guidelines

Source voltage using series SMUs

Maximum Pulsed Signal Levels for Model 2651A:

80 V with 45 A compliance

SMU 1 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Normal output-off current limit:
smuX.source.offlimiti = 1e-3 (default)
Current compliance must be 10% higher than the current compliance
of SMU 2. Current compliance limit (maximum):
smuX.trigger.source.limiti = 50
The polarity of SMU 1 is generally the opposite of the desired voltage

polarity across the device. To achieve a positive voltage across the
device, program SMU 1 to a negative voltage level. For example, to
output 80 V across the device, program SMU 1 to -40 V and SMU 2 to
+40 V. To achieve a negative voltage across the device, program
SMU 1 to a positive voltage level and SMU 2 to a negative voltage
level.
Source polarity changes incur a 100 µs penalty. The number 0 is
considered a positive value. For negative-going pulses with a 0 V bias
level, avoid the time penalty by programming a negative number very
near zero, for example, -1e-12 V.

SMU 2 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Normal output-off current limit (0.9 mA which is 10% less than the
SMU 1 smuX.source.offlimiti):
smuX.source.offlimiti = 0.9e-3
Current compliance must be 10% lower than the current compliance of

SMU 1. Therefore, this SMU will control the maximum current through
the DUT. Current compliance limit (maximum):
smuX.trigger.source.limiti = 45

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SourceMeter instrument configuration

Guidelines

Source voltage with extended current using
parallel SMUs

Maximum Pulsed Signal Levels for Model 2651A:

36 V with 95 A compliance

SMU 1 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Normal output-off current limit:
smuX.source.offlimiti = 1e-3 (default)
The current compliance of SMU 1 (V-source) must be 10% greater
than that maximum programmed current of SMU 2 (I-source)
Current compliance limit (maximum):
smuX.trigger.source.limiti = 50

SMU 2 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCAMPS
Normal output-off voltage limit (40 V maximum):
smuX.source.offlimitv = 40
The voltage compliance of SMU 2 (I-source) must be 10% greater
than the maximum programmed voltage of SMU 1 (V-source).
Voltage compliance limit (maximum):
smuX.trigger.source.limitv = 40

For all configurations

▪ When combining Model 2651A SMUs, restrict operation to

pulse only

▪ For comparable rise times, the source range and level of

SMU 1 must match the source range and level of SMU 2

▪ The programmed current and voltage levels for both SMUs

must fall within the same pulse region. See the figure titled
"SMU pulse regions when combining SMUs" for a definition of
pulse regions (earlier in this topic)

▪ Placing two voltage sources in parallel is not recommended
▪ Placing two current sources in series is not recommended
▪ Think carefully about the appropriate output-off mode

(smuX.source.offmode) and output-off function
(smuX.source.offfunc) whenever changes are made to the
source function. The alternative is to always use the high
impedance output-off mode (smuX.source.offmode =
smuX.OUTPUT_HIGH_Z).

Combining channels in series to output higher voltage

Channels in series cause hazardous voltage (>30 V

RMS

, 42 V

PEAK

) to be present and accessible
at the Model 2651A output connector. A safety shield must be used whenever hazardous
voltages will be present in the test circuit. To prevent electrical shock that could cause injury
or death, never use the Model 2651A in a test circuit that may contain hazardous voltages
without a properly installed and configured safety shield.

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Higher pulse voltage can be output by connecting two (and only two) Model 2651A instrument's
channels in series. When combining two SMU channels, make sure both SMUs have the same model
number.

The following figure illustrates two Model 2651As configured with the two channels connected in
series to output up to 80 V (40 V per channel).

Whenever hazardous voltage (>30 V

RMS

, 42 V

PEAK

) will be output, a safety shield must completely
surround the DUT test circuit. When using a metal safety shield, it must be connected to a known
safety earth ground and chassis ground.

Figure 17: Connecting channels in series for higher voltage

(1) First Model 2651A: SMU maximum pulse voltage: −40 V
(2) Second Model 2651A: SMU maximum pulse voltage: +40 V
(3) Series SMU maximum pulse voltage (as shown): 80 V

For further information, visit tek.com\keithley (tek.com/keithley) for application notes on combining
SMU channels.

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Combining channels in parallel to output higher current

You can output higher pulse current by connecting the channels of two Model 2651A instruments in
parallel. When combining two SMU channels, make sure both SMUs have the same model number.

The figure below illustrates the connection scheme of two Model 2651A instruments connected in
parallel. Two Model 2651A can output up to 100 A at 36 V (see Combining SMU outputs (on page
2-51)). The current delivered to the DUT is the sum of currents output by SMU channels (IT).
Combining the two Model 2651A instruments expands the power envelope. For further information,
visit tek.com/keithley for application notes on combining the channels of two Model 2651A
instruments.

Figure 18: Connecting channels in parallel for higher current

I1 Single SMU maximum pulse current: 50 A
I2 Single SMU maximum pulse current: 50 A
IT Paralleled SMU channels maximum pulse current (as shown): 100 A

Guarding and shielding

You can optimize source-measure performance and safety with the effective use of guarding and
shielding (noise and safety shields).

Safety shield

A safety shield must be used whenever hazardous voltages (>30 V

RMS

, 42 V

PEAK

) will be
present in the test circuit. To prevent electrical shock that could cause injury or death, never
use the Model 2651A in a test circuit that may contain hazardous voltages without a properly
installed and configured safety shield.

The safety shield can be metallic or nonconductive and must completely surround the device under
test (DUT) test circuit. A metal safety shield must be connected to a known protective earth (safety
ground). See Test fixtures (on page 2-61) for important safety information on the use of a metal or a
nonconductive enclosure.

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Safety shielding and hazardous voltages

The maximum output voltage for a Model 2651A channel is 40 V, which is considered a
nonhazardous level. However, using two Model 2651A voltage sources in a series configuration or

floating a SMU (on page 2-63) can cause test circuit voltage to exceed 42 V. In the following figure,

the source-measure units (SMUs) of two Model 2651A instruments can be connected in series to
apply 80 V to a device under test (DUT) (see TSP advanced features (on page 6-61) for information
on using multiple Model 2651A).

Use #18 AWG wire or larger for connections to safety earth ground and chassis.

Figure 19: Safety shield for hazardous voltage using two Model 2651A instruments

Guarding

A driven guard is always enabled and provides a buffered voltage that is at the same level as the
input/output HI voltage. The purpose of guarding is to eliminate the effects of leakage current (and
capacitance) that can exist between HI and LO. Without guarding, leakage and capacitance in the
external high-impedance test circuit could be high enough to adversely affect the performance of the
Model 2651A.

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Guarding (shown below) is recommended when test circuit impedance is >1 GΩ.

See Guard (on page 4-23) for details on the principles of guarding.

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

Figure 20: High-impedance guarding

Noise shield

Use a noise shield (see following figure) to prevent unwanted signals from being introduced into the
test circuit. Low-level signals may benefit from effective shielding. The metal noise shield surrounds
the test circuit and should be connected to LO, as shown.

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

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Connections to LO on the Model 2651A are not necessarily at 0 V. Hazardous voltages could
exist between LO and chassis ground. Make sure that high-voltage precautions are taken
throughout the test system. Alternatively, limit hazardous levels by adding external
protection to limit the voltage between LO and chassis. Failure to make sure high-voltage
precautions are used throughout the test system or a failure to limit hazardous levels could
result in severe personal injury or death from electric shock.

Figure 21: Noise shield

Using shielding and guarding together

The following figures show connections for a test system that uses a noise shield, a safety shield, and
guarding. The guard shields are connected to the driven guard (GUARD) of the SMU. The noise
shield is connected to LO. The safety shield is connected to the chassis and to protective earth
(safety ground).

Guard voltage can be hazardous. With an unguarded device under test (DUT) connection,
terminate the guard before the end of the cable. Connect the enclosure of all metal test
fixtures to protective earth (safety ground). See your specific test fixture for information.
Nonconductive test fixtures must be rated to double the maximum capability of the test
equipment in the system.

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Figure 22: Connections for noise shield, safety shield, and guarding

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Test fixture

A test fixture can be used to house a device or test circuit. The test fixture can be a metal or
nonconductive enclosure, and is typically equipped with a lid. When the test fixture is correctly
connected, the output of the Model 2651A will turn off when the lid of the test fixture is opened.

You mount the test circuit inside the test fixture.

▪

To provide protection from shock hazards, an enclosure should be provided that
surrounds all live parts.

Nonconductive enclosures must be constructed of materials that are suitably rated for
flammability and the voltage and temperature requirements of the test circuit. Connect the
enclosure of all metal test fixtures to protective earth (safety ground). See your specific
test fixture for information. Nonconductive test fixtures must be rated to double the
maximum capability of the test equipment in the system.

For metallic enclosures, the test fixture chassis must be properly connected to protective
earth (safety ground). A grounding wire (16 AWG or larger) must be attached securely to
the test fixture at a screw terminal designed for safety grounding. The other end of the
ground wire must be attached to a known protective earth (safety ground).

▪ When hazardous voltages (>30 V

RMS

, 42 V

PEAK

) will be present, the test fixture must meet

the following safety requirements:

▪ Construction material: A metal test fixture must be connected to a known protective earth

(safety ground) as described in the above warning. A nonconductive test fixture must be
constructed of materials that are suitable for flammability, voltage, and temperature
conditions that may exist in the test circuit. The construction requirements for a
nonconductive enclosure are also described in the warning above.

▪ Test circuit isolation: With the lid closed, the test fixture must completely surround the

test circuit. A metal test fixture must be electrically isolated from the test circuit. Although
the outer layer on a high voltage triaxial cable must be connected to the test fixture's
metal chassis, the inner two layers of the cable (input/output connectors) must be
isolated from the test fixture. Internally, Teflon standoffs are typically used to insulate the
internal printed circuit board or guard plate for the test circuit from a metal test fixture.

▪ Interlock switch: The test fixture must have a normally-open interlock switch. The

interlock switch must be installed so that when the lid of the test fixture is opened, the
switch will open, and when the lid is closed, the switch will close. The Model 2651A digital
I/O port provides an output enable line. When properly used with a test fixture, the output
of the Model 2651A turns off when the lid of the test fixture is opened.

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The digital I/O port of the Model 2651A is not suitable for control of safety circuits and should
not be used to control a safety interlock.

See Digital I/O (on page 3-92) for information on the digital I/O port.

Floating a SMU

Using an external source in the test system may require that a Model 2651A source-measure unit
(SMU) float off chassis earth ground. An example of such a test system is shown below, which
includes an external voltage source. Notice that output LO of the external voltage source is connected
to chassis earth ground.

For the test circuit shown below, the Model 2651A must float off chassis earth ground. As shown, LO
of the Model 2651A is floating +10 V above chassis earth ground. If LO of the Model 2651A was
instead connected to chassis ground, the external voltage source would be shorted to the chassis
ground.

Figure 23: Floating the Model 2651A schematic

The Model 2651A connections for the floating configuration are shown below. In order to float the
SMU, input/output LO must be isolated from chassis ground. This is accomplished by not connecting
input/output LO to chassis ground.

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Figure 24: Floating the 2651A SMU connections

The external voltage source can be a SMU of a second Model 2651A instrument or other instrument.
Keep in mind that if the combined outputs of the sources exceeds 42 V, then a safety shield will be
required for the DUT (see the following WARNINGS).

The maximum floating (common mode) voltage for a SMU is ±250 V. Exceeding this level may
cause damage to the instrument and create a shock hazard.

Using an external source to float a SMU could create a shock hazard in the test circuit. A
shock hazard exists whenever >42 V peak is present in the test circuit. Appropriately rated
cables or insulators must be provided for all connections to prevent access to live parts.

When >42 V is present, the test circuit must be insulated for the voltage used or surrounded
by a metal safety shield that is connected to a known protective earth (safety ground) and
chassis ground (see Safety shield (on page 2-57)).

DUT connection settings

Make sure to properly configure the Model 2651A sense mode for the specific DUT test connection
scheme. Use care to configure both the output-off state protection settings to supplement safe
operation of your test setup.

Sense mode selection

You can set the sense mode to use 2-wire local sensing connections (on page 2-47) or 4-wire remote

sensing connections (on page 2-47). The default sense setting is 2-wire local.

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Front-panel sense mode selection

To check or change the voltage sense mode from the front panel:

1. Press the CONFIG key.

2. Press the SRC or MEAS key. You can access and set the Model 2651A sense mode from either

the V-SOURCE or the V-MEAS menu items.

3. If you pressed the SRC key: Select V-SOURCE > SENSE-MODE, and then press the ENTER

key or the navigation wheel.
If you pressed the MEAS key: Select V-MEAS > SENSE-MODE, and then press the ENTER key

or the navigation wheel.

4. Select 2-WIRE or 4-WIRE as needed, and then press the ENTER key or the navigation wheel.

Selecting the sense from a remote interface

To select the remote sense from a remote interface:

Set the smua.sense attribute to control the sense state by remote. The programming example below
illustrates how to configure the Model 2651A for 4-wire remote sensing:

smua.sense = smua.SENSE_REMOTE

See Remote source-measure commands (on page 2-29) and TSP command reference (on page 7-1)
for details.

Output-off states

Carefully consider and configure the appropriate output-off state, source function, and
compliance limits before connecting the Model 2651A to a device that can deliver energy (for
example, other voltage sources, batteries, capacitors, solar cells, or other Model 2651A
instruments). Configure recommended instrument settings before making connections to the
device. Failure to consider the output-off state, source, and compliance limits may result in
damage to the instrument or to the device under test (DUT).

Output-off modes

Turning off the Model 2651A output may not completely isolate the instrument from the external circuit.
You can use the output-off mode to place the Model 2651A in a noninteractive state during idle
periods. The available output-off modes are normal, high-impedance, and zero.

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Normal output-off mode

The normal output-off mode is the default output-off mode setting. When the source-measure unit
(SMU) is in the normal output-off mode, you can select either the current or the voltage output-off
function (see Output-off function (on page 2-67)). You can also specify current and voltage output-off
limits (Output-off limits (compliance) (on page 2-68)).

When the output is turned off, the output goes to either 0 V or 0 A, depending on the selected
output-off function. Voltage is the default output-off function.

High-impedance output-off mode

For the high-impedance output-off mode (HI-Z), the output relay opens when the output is turned off.
This disconnects external circuitry from the input/output of the source-measure unit (SMU). To
prevent excessive wear on the output relay, do not use this output-off mode for tests that turn the
output off and on frequently.

Zero output-off mode

When the zero output-off mode is selected, the programmed source remains on the display, but
internally, the voltage source is selected and is set to 0 V. Measurements are made and displayed.

When the selected source is voltage, the current compliance setting remains the same as the
output-on value and compliance detection remains active.

When the selected source is current, the current compliance setting is the programmed current
source value or 10 percent full-scale of the present current range, whichever is greater.

You can use the Model 2651A as a current meter when it is in zero output-off mode because it
outputs 0 V but measures current.

To configure the output-off mode from the front panel:

1. Press the CONFIG key.

2. Press the OUTPUT ON/OFF control. The CONFIGURE OUTPUT A menu is displayed.

3. In the CONFIGURE OUTPUT A menu, select OFF-STATE to display the OUTPUT OFF STATE

A menu.

4. With the OUTPUT OFF STATE A menu displayed, select MODE to open the OFF MODE A

menu.

5. Select the output-off mode: HI-Z (high-impedance), NORMAL, or ZERO.

To select the normal output-off mode over a remote interface:

smua.source.offmode = smua.OUTPUT_NORMAL

To select the high-impedance output-off mode over a remote interface:

smua.source.offmode = smua.OUTPUT_HIGH_Z

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To select the zero output-off mode over a remote interface:

smua.source.offmode = smua.OUTPUT_ZERO

Output-off function

This setting is used only when the output is turned off and the Model 2651A is set to the normal
output-off mode (smua.source.offmode = smua.OUTPUT_NORMAL).

You can set the output-off function to CURRENT or VOLTAGE through the CONFIG menu on the
front panel, or by using the smua.source.offfunc attribute from a remote interface. VOLTAGE is
the default output-off function.

When the output is turned off and the selected output-off function is VOLTAGE
(smua.source.offfunc = smua.OUTPUT_DCVOLTS):

• The source-measure unit (SMU) sources 0 V.

• The current limit is set by the smua.source.offlimiti attribute (default 1 mA).

When the output is turned off and the selected output-off function is CURRENT
(smua.source.offfunc = smua.OUTPUT_DCAMPS):

• The SMU sources 0 A.

• The voltage limit is set by the smua.source.offlimitv attribute (default 40 V).

When the output-off function is set to either voltage or current, the SMU may source or sink a very
small amount of power. In most cases, this source or sink power level is insignificant.

Selecting the output-off function

This setting is used only when the output is turned off and the source-measure unit (SMU) is in
NORMAL output-off mode.

To configure the output-off function from the front panel:

1. Press the CONFIG key.

2. Press the OUTPUT ON/OFF control. The CONFIGURE OUTPUT A menu is displayed.

3. In the CONFIGURE OUTPUT A menu, select OFF-STATE to display the OUTPUT OFF STATE

A menu.

4. With the OUTPUT OFF STATE A menu displayed, select FUNCTION to display the OFF

FUNCTION A menu.

5. In the OFF FUNCTION A menu, select CURRENT or VOLTAGE.

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To configure the output-off function remotely:

To set 0 V output with current limit set by the smua.source.offlimiti attribute:

smua.source.offfunc = smua.OUTPUT_DCVOLTS

To set 0 A output with voltage limit set by the smua.source.offlimitv attribute:

smua.source.offfunc = smua.OUTPUT_DCAMPS

Output-off limits (compliance)

You can set output-off limits (compliance) for the current and voltage output-off functions using the
CONFIG menu on the Model 2651A front panel, or by setting the smua.source.offlimitY
attribute from a remote interface. The output-off limits only apply when the output-off mode is normal.

Setting output-off limits

Setting the output-off limit for CURRENT (smua.source.offlimiti) specifies the current limit for
the voltage source; setting the output-off limit for VOLTAGE (smua.source.offlimitv) specifies
the voltage limit for the current source.

To configure output-off limits from the front panel:

1. Press the CONFIG key.

2. Press the OUTPUT ON/OFF control. The CONFIGURE OUTPUT A menu is displayed.

3. In the CONFIGURE OUTPUT A menu, select OFF-STATE to display the OUTPUT OFF STATE

A menu.

4. With the OUTPUT OFF STATE A menu displayed, select LIMIT to display the OFF LIMIT A

menu.

5. In the OFF LIMIT A menu, select CURRENT or VOLTAGE.

6. Use the left or right arrow keys or turn the navigation wheel to select the current or voltage limit,

and then press the ENTER key or the navigation wheel to save your settings.

7. Press the EXIT key as needed to return to the previous menu or display.

To set the current limit in NORMAL output-off mode remotely:

smua.source.offlimiti = iValue

To set the voltage limit in NORMAL output-off mode remotely:

smua.source.offlimitv = vValue

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Remote programming output-off states quick reference

The content of the following table is a quick reference of commands for programming output-off states
from a remote interface.

Output-off state programming quick reference

Command

Description

smua.source.offmode = smua.OUTPUT_NORMAL

Selects normal output-off mode.

smua.source.offmode = smua.OUTPUT_HIGH_Z

Selects high-impedance output-off mode.

smua.source.offmode = smua.OUTPUT_ZERO

Selects zero output-off mode.

smua.source.offfunc = smua.OUTPUT_DCVOLTS

Sets 0 V output with current limit specified by
the smua.source.offlimiti attribute.

smua.source.offfunc = smua.OUTPUT_DCAMPS

Sets 0 A output with voltage limit specified by
the smua.source.offlimitv attribute.

smua.source.offlimiti = iValue

Sets current limit in normal output-off mode.

smua.source.offlimitv = vValue

Sets voltage limit in normal output-off mode.

USB storage overview

The Model 2651A includes a USB port on the front panel. To store scripts and to transfer files from
the instrument to the host computer, you need a USB flash drive.

• For information about saving reading buffers to a USB flash drive, see Saving reading buffers (on

page 3-9).

• For information about storing and loading scripts to and from a USB flash drive, see Save a user

script (on page 6-11).

• For information about file I/O, see File I/O (on page 5-7).

• For information about saving user setups, see Saved setups (on page 2-42).

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Connecting the USB flash drive

The Model 2651A supports flash drives that comply with USB 2.0 standards (as well as USB 1.0 and

1.1 standards). You can save data to the USB flash drive from the front panel, or you can create a
script to save data to the USB flash drive.

To connect the USB flash drive, plug the USB flash drive into the USB port located on the
instrument's front panel (see the figure below).

Figure 25: USB port

File system navigation

The Model 2651A can use commands from the Lua fs library to navigate and list files that are
available on a flash drive. These Lua commands are in the fs command group in the instrument.

The fs commands make the file system of any given node available to the entire TSP-Link® system.
For example, you can use the command node[5].fs.readdir(".") to read the contents of the
current working directory on node 5.

The root folder of the USB flash drive has the absolute path:
"/usb1/"

You can use either the slash (/) or backslash (\) as a directory separator. However, the backslash is
also used as an escape character, so if you use it as a directory separator, you generally need to
use a double backslash (\\) when you are creating scripts or sending commands to the instrument.

The instrument supports the following Lua fs commands:

fs.chdir() (on page 7-114)
fs.cwd() (on page 7-115)
fs.is_dir() (on page 7-116)
fs.is_file() (on page 7-117)
fs.mkdir() (on page 7-118)
fs.readdir() (on page 7-119)
fs.rmdir() (on page 7-120)

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The following Lua fs commands are not supported:

fs.chmod()
fs.chown()
fs.stat()

Displayed error and status messages

During operation and programming, front-panel messages may be briefly displayed. Typical
messages are either status or error notifications (refer to the Error summary list (on page 8-3) for a
complete list of these messages and their meanings).

Status and error messages are held in a queue. For information about retrieving messages from
queues, refer to Queues (on page 15-2). For information about error messages, refer to the

Troubleshooting guide (on page 8-1).

Range

The selected measurement range affects the accuracy of the measurements and the maximum signal
that can be measured. If the range is changed, the front-panel display may contain dashes instead of
a reading (for example, --.---- mA). This indicates that no measurement was made using the range
that is presently selected. To update the displayed reading, trigger a measurement (if in local control,
press the TRIG key).

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Available ranges

The following table lists the available source and measurement ranges for the Keithley Instruments
Model 2651A High Power System SourceMeter® Instrument.

Model 2651A source and measurement ranges

Voltage ranges

Current ranges

100 mV

1 µA

1 V

10 µA

10 V

100 µA

20 V

1 mA

40 V

10 mA

100 mA

1 A 5 A* 10 A*

20 A*

50 A**

* Refer to Operating boundaries (on page 4-5) for power derating information.
** 50 A range accessible only in pulse mode.

Maximum source values and readings

The full-scale output for each voltage and current source range is 101 percent of the selected range,
but the full-scale measurement is 102 percent of the range. For example, ±1.01 A is the full-scale
source value for the 5 A range, and ±102 mA is the full-scale reading for the 100 mA measurement
range. Input levels that exceed the maximum levels cause the overflow message to be displayed.
Note, however, that the instrument will autorange at 100 percent of the range.

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Measure autodelay

The measure delay is a specific delay that is applied before each measurement is made. This delay is
disabled by default (measurements are made immediately). You can change the default delay by
setting the smuX.measure.delay (on page 7-248) attribute either to a specific value or to an autodelay
setting (set smua.measure.delay = smua.DELAY_AUTO). If the measure delay is set to the
autodelay setting, a range-dependent delay is applied each time the instrument performs a current
measurement. This delay also happens for the measurement that is made after changing current
ranges during an autoranged measurement. The following table contains the measure autodelays
associated with each current range.

Range

Measure autodelay

10 mA (and above)

0 µs (no delay)

1 mA

100 µs

100 µA

150 µs

10 µA

500 µs

1 µA

2.5 ms

100 nA

15 ms

You can increase or decrease the autodelay by changing the delay factor (for example, to reduce the
delay across all ranges by half, set smua.measure.delayfactor = 0.5). For additional information,
refer to smuX.measure.delayfactor (on page 7-249).

Ranging limitations

If the source and measure functions are different (such as source V and measure I, or source I and
measure V), you can set source and measure ranges separately. If both source and measure
functions are the same, the measure range is locked to the source range.

The maximum output power and source/sink limit for the Model 2651A is 202 W per channel
(maximum). With the 40 V (V-Source) range selected, the highest current measurement range is 5 A.
Refer to Operating boundaries (on page 4-5) for power derating information. When pulsing with the 50
A I-Source range selected, you can be at a larger voltage range than 4 V dependent on your duty
cycle. See Pulse duty cycle (on page 3-30) for details.

Manual ranging

Use the range keys, and , to select a fixed range:

• To set the source range, press the SRC key, and then use the RANGE keys to set the range.

• To set the measure range, press the MEAS key, and then use the RANGE keys to set the range.

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If the instrument displays the overflow message on a particular range, select a higher range until an
on-range reading is displayed. To ensure the best accuracy and resolution, use the lowest range
possible that does not cause an overflow.

Autoranging

To use automatic source ranging, press SRC then the AUTO range key.
To use automatic measure ranging, press the MEAS key followed by the AUTO range key. The

AUTO indicator turns on when source or measure autoranging is selected.
When autorange is selected, the instrument automatically sets the best range to source or measure

the applied signal. The instrument increases the range to 100 percent of the present range.

When you change a source value, source autoranging is automatically turned off and remains off
until you re-enable it.

Low range limits

The low range limit sets the lowest range that the Model 2651A uses when autoranging is enabled.
This feature is useful for minimizing autorange settling times when measurements require numerous
range changes.

To individually set low range limits for Source V, Source I, Measure V, and Measure I:

1. Press the CONFIG key, then press either the SRC key (for source) or the MEAS key (for

measure).

2. Select voltage or current source, or measure, as appropriate, and then press the ENTER key or

the navigation wheel.

3. Select LOWRANGE, and then press the ENTER key or the navigation wheel.

4. Set the low range to the appropriate setting, and then press the ENTER key or the navigation

wheel.

5. Press the EXIT (LOCAL) key twice to return to the main display.

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Range considerations

The source range and measure range settings can interact depending on the source function.
Additionally, the output state (on/off) can affect how the range is set. The following table describes
these interactions:

If...

Then...

Notes

The source function is
the same as the
measurement function
(for example, sourcing
voltage and
measuring voltage)

The measurement
range is locked to be
the same as the
source range.

The setting for the voltage measure range is retained and used when the
source function is changed to current.
Model 2651A example:

smua.source.func = smua.OUTPUT_DCVOLTS
smua.source.rangev = 1
smua.measure.rangev = 10

-- will print 1, the source range
print(smua.measure.rangev)
smua.source.func = smua.OUTPUT_DCAMPS

-- will print 10, the measure range
print(smua.measure.rangev)

A source or
measurement range
for a function is
explicitly set

Autoranging for that
function is disabled.

Autoranging is controlled separately for each source and measurement
function: source voltage, source current, measure voltage, and measure
current. Autoranging is enabled for all four by default.

Source autoranging is
enabled

The output level
controls the range.

Querying the range after the level is set returns the range the instrument
chose as appropriate.

You send a source
level that is out of
range while autorange
is off (an example of
this is sending 1 A on
the 100 mA range)

The instrument will
not return an error
until the output is
turned on.

When the output is turned on, the display will show a series of question
marks: ???.???
Measure autoranging
is enabled

The measure range is
changed only when a
measurement is
taken.

Querying the range after the measurement is taken will return the range
that the instrument chose.