Keithley 2750 User Manual

Model 2750 Multimeter/Switch System

A GREATER MEASURE OF CONFIDENCE

User’s Manual

WARRANTY

Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a
period of 3 years from date of shipment.

Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables,
rechargeable batteries, diskettes, and documentation.

During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.

To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in
Cleveland, Ohio. You will be given prompt assistance and return instructions. Send the product, transportation
prepaid, to the indicated service facility. Repairs will be made and the product returned, transportation prepaid.
Repaired or replaced products are warranted for the balance of the original warranty period, or at least 90 days.

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written
consent, or misuse of any product or part. This warranty also does not apply to fuses, software, non-rechargeable
batteries, damage from battery leakage, or problems arising from normal wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING
ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE
REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR
ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT
OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS
BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED
DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL AND
INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE
TO PROPERTY.

Keithley Instruments, Inc.

Sales Offices: BELGIUM:

CHINA:

Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-82251886 • Fax: [phone]

FINLAND:
FRANCE:
GERMANY:
GREAT BRITAIN:
INDIA:

1/5, Eagles Street • Langford Town • Bangalore 560 025 • 080 212 80-27 • Fax: [phone]

ITALY:

Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: [phone]

JAPAN:

New Pier Takeshiba North Tower 13F • 11-1, Kaigan 1-chome • Minato-ku, Tokyo 105-0022 • 81-3-5733-7555 • Fax: [phone]

KOREA:

2FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-888 • 82-2-574-7778 • Fax: [phone]

NETHERLANDS:
SWEDEN:
TAIWAN:

28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]

1-888-KEITHLEY (534-8453) • www.keithley.com

Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: [phone]

Halsuantie 2 • 00420 Helsinki, Finland • 09-53 06 65 60 • Fax: [phone]

3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: [phone]

Landsberger Strasse 65 • 82110 Germering • 089-84 93 07-40 • Fax: [phone]

Unit 2 Commerce Park, Brunel Road • Theale, Berkshire RG7 4AB • 0118 -929 75 00 • Fax: [phone]

Postbus 559 • 4200 AN Gorinchem • 0183-63 53 33 • Fax: [phone]

c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 16970 Solna • 08-50 90 46 00 • Fax: [phone]

13F-3, NO. 6, Lane 99, Pu-Ding Road, Hsinchu, Taiwan, ROC. • 886-3-572-9077• Fax: [phone]

5/03

Model 2750 Multimeter/Switch System

User’s Manual

©2001, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Fourth Printing, August 2003

Document Number: 2750-900-01 Rev. D

Manual Print History

The print history shown below lists the printing dates of all Revisions and Addenda created
for this manual. The Revision Level letter increases alphabetically as the manual undergoes
subsequent updates. Addenda, which are released between Revisions, contain important change
information that the user should incorporate immediately into the manual. Addenda are
numbered sequentially. When a new Revision is created, all Addenda associated with the
previous Revision of the manual are incorporated into the new Revision of the manual. Each new
Revision includes a revised copy of this print history page.

Revision A (Document Number 2750-900-01).............................................................. March 2001

Revision B (Document Number 2750-900-01) ........................................................November 2001

Revision C (Document Number 2750-900-01) ........................................................November 2002

Revision D (Document Number 2750-900-01).............................................................August 2003

All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Other brand names are trademarks or registered trademarks of their respective holders.

S

afety 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 non-hazardous voltages, there are situations where hazardous
conditions may be present.

This product is intended for use by qualified 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 manual for complete product specifications.

If the product is used in a manner not specified, the protection provided by the product may be impaired.

The types of product users are:

Responsible body

ment is operated within its specifications and operating limits, and for ensuring that operators are adequately trained.

Operators

instrument. They must be protected from electric shock and contact with hazardous live circuits.

Maintenance personnel

voltage or replacing consumable materials. Maintenance procedures are described in the manual. The procedures explicitly state
if the operator may perform them. Otherwise, they should be performed only by service personnel.

Service personnel

trained service personnel may perform installation and service procedures.

Keithley products are designed for use with electrical signals that are rated Measurement Category I and Measurement Category
II, as described in the International Electrotechnical Commission (IEC) Standard IEC 60664. Most measurement, control, and
data I/O signals are Measurement Category I and must not be directly connected to mains voltage or to voltage sources with
high transient over-voltages. Measurement Category II connections require protection for high transient over-voltages often
associated with local AC mains connections. Assume all measurement, control, and data I/O connections are for connection to
Category I sources unless otherwise marked or described in the Manual.

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 30V RMS,

42.4V peak, or 60VDC are present.

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 volts,

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, make sure 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.

is the individual or group responsible for the use and maintenance of equipment, for ensuring that the equip-

use the product for its intended function. They must be trained in electrical safety procedures and proper use of the

perform routine procedures on the product to keep it operating properly, for example, setting the line

are trained to work on live circuits, and perform safe installations and repairs of products. Only properly

A good safety practice is to expect that hazardous voltage is present in any unknown

no conductive part of the circuit may be exposed.

5/03

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.

The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the
equipment may be impaired.

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

When fuses are used in a product, replace with same type and rating for continued protection against fire hazard.

Chassis connections must only be used as shield connections for measuring circuits, NOT as safety earth 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 safety earth ground using the wire recommended in the user documentation.

!

The symbol on an instrument indicates that the user should refer to the operating instructions located in the manual.

The symbol on an instrument shows that it can source or measure 1000 volts or more, including the combined effect of
normal and common mode voltages. Use standard safety precautions to avoid personal contact with these voltages.

The symbol indicates a connection terminal to the equipment frame.

The

WARNING

information very carefully before performing the indicated procedure.

The

CAUTION

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 Instruments. Standard fuses, with applicable national safety
approvals, may be used if the rating and type are the same. 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 Instruments to maintain accuracy and functionality of the product.) If you are unsure about the applicability
of a replacement component, call a Keithley Instruments office for information.

To clean an instrument, use a damp cloth 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., 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.

heading in a manual explains dangers that might result in personal injury or death. Always read the associated

heading in a manual explains hazards that could damage the instrument. Such damage may invalidate the

Table of Contents

1 Getting Started

General information ................................................................... 1-2

Warranty information .......................................................... 1-2

Contact information ............................................................ 1-2

Safety symbols and terms ................................................... 1-2

Inspection ............................................................................ 1-3

Options and accessories ...................................................... 1-3

Model 2750 features ................................................................... 1-6

Plug-in switching modules ......................................................... 1-7

Pseudocards ......................................................................... 1-9

Identifying installed switching modules ........................... 1-10

Front and rear panel familiarization ......................................... 1-10

Front panel summary ........................................................ 1-10

Rear panel summary ......................................................... 1-14

Rack mounting ......................................................................... 1-15

Power-up .................................................................................. 1-16

Line power connection ...................................................... 1-16

Line frequency .................................................................. 1-16

Setting line voltage and replacing fuse ............................. 1-17

Power-up sequence ........................................................... 1-18

Keyclick ............................................................................ 1-19

Display ..................................................................................... 1-19

Status and error messages ................................................. 1-19

Remote programming — display ...................................... 1-20

Defaults and user setups ........................................................... 1-21

Saving and restoring setups .............................................. 1-22

Remote programming — default and user setups ............. 1-26

Remote programming information ........................................... 1-27

Quick start exercises ................................................................. 1-28

Basic DMM measurements — front panel inputs ............. 1-28

Closing and opening channels — system channel

Simple scanning ................................................................ 1-34

Trigger and return readings — remote programming ....... 1-37

operation ......................................................................... 1-31

2 Closing and Opening Switching Module Channels

Close/open overview .................................................................. 2-2

Switching module installation and connections ......................... 2-3

Module installation ............................................................. 2-3

Connections ......................................................................... 2-4

Pseudocards ......................................................................... 2-5

Channel assignments .................................................................. 2-5

System channel operation ........................................................... 2-6

2-wire functions ................................................................... 2-7

4-wire functions (paired channels) ...................................... 2-8

Controlling the system channel ........................................... 2-9

Non-amp and non-measure switching modules ................ 2-14

Multiple channel operation ....................................................... 2-16

Controlling multiple channels ........................................... 2-17

Multiple channel operation anomalies .............................. 2-22

Dual independent multiplexers .......................................... 2-24

Identifying installed modules and viewing closed channels .... 2-29

CARD menu ...................................................................... 2-29

Switching module queries (remote operation) .................. 2-31

Relay closure count .................................................................. 2-32

Reading relay closure count .............................................. 2-33

Setting count update interval ............................................. 2-34

Model 7700 switching module ................................................. 2-34

Switching module capabilities .......................................... 2-34

Schematic diagram ............................................................ 2-36

3 Basic DMM Operation

DMM measurement capabilities ................................................. 3-2

High energy circuit safety precautions ....................................... 3-3

Performance considerations ........................................................ 3-4

Warm-up .............................................................................. 3-4

Autozero .............................................................................. 3-4

LSYNC (line cycle synchronization) .................................. 3-5

Remote programming — autozero and LSYNC ................. 3-6

Channel list parameter (<clist>) ................................................. 3-6

Voltage measurements (DCV and ACV) .................................... 3-7

DCV input divider ............................................................... 3-7

Connections ......................................................................... 3-8

Volts measurement procedure ........................................... 3-11

AC voltage measurements and crest factor ....................... 3-12

Low level considerations ................................................... 3-15

Current measurements (DCI and ACI) ..................................... 3-16

Connections ....................................................................... 3-16

Amps measurement procedure .......................................... 3-18

AMPS fuse replacement (front panel AMPS input) .......... 3-19

Resistance measurements (Ω2 and Ω4) ................................... 3-19

Connections ....................................................................... 3-20

Standard resistance measurements .................................... 3-23

Offset-compensated ohms ................................................. 3-24

Dry circuit ohms (DRYCKT) ............................................ 3-26

Measurement methods ...................................................... 3-28

4-wire common-side (CSID) ohms measurements

(7701 module) ................................................................ 3-34

Temperature measurements ...................................................... 3-35

Thermocouples .................................................................. 3-35

Thermistors ....................................................................... 3-38

4-wire RTDs ...................................................................... 3-38

Connections ....................................................................... 3-39

Temperature measurement configuration .......................... 3-44

Temperature measurement procedure ............................... 3-46

Frequency and period measurements ....................................... 3-47

Trigger level ...................................................................... 3-47

Gate time ........................................................................... 3-47

Connections ....................................................................... 3-48

Frequency and period measurement procedure ................ 3-49

Continuity testing ..................................................................... 3-50

Connections ....................................................................... 3-50

Continuity testing procedure ............................................. 3-51

Remote programming for basic measurements ........................ 3-52

Basic measurement commands ......................................... 3-52

Basic measurement programming examples .................... 3-58

Measurement queries ............................................................... 3-60

:FETCh? ............................................................................ 3-60

:READ? ............................................................................. 3-60

:MEASure[:<function>]? .................................................. 3-61

[:SENSe[1]]:DATA:FRESh? ............................................. 3-62

[:SENSe[1]]:DATA[:LATest]? .......................................... 3-62

Examples ........................................................................... 3-63

4 Range, Digits, Rate, Bandwidth, and Filter

Range ......................................................................................... 4-2

Measurement ranges and maximum readings ..................... 4-2

Manual ranging ................................................................... 4-3

Auto ranging ....................................................................... 4-3

Scanning .............................................................................. 4-3

Remote programming — range .......................................... 4-4

Digits .......................................................................................... 4-5

Scanning .............................................................................. 4-6

Remote programming — digits .......................................... 4-6

Rate and bandwidth .................................................................... 4-8

Rate ...................................................................................... 4-8

Bandwidth ......................................................................... 4-10

Scanning ............................................................................ 4-10

Remote programming — rate and bandwidth ................... 4-10

Filter ......................................................................................... 4-13

Filter characteristics ......................................................... 4-13

Remote programming — filter .......................................... 4-20

5 Relative, Math, Ratio, Channel Average, and dB

Relative ....................................................................................... 5-2

Basic operation .................................................................... 5-2

Remote programming — rel ............................................... 5-4

Math ............................................................................................ 5-7

mX+b ................................................................................... 5-8

Percent ................................................................................. 5-9

Reciprocal (1/X) ................................................................ 5-10

Basic operation .................................................................. 5-11

Remote programming — math .......................................... 5-12

Ratio and channel average ........................................................ 5-14

Basic operation .................................................................. 5-15

Remote programming — ratio and channel average ......... 5-17

dB ............................................................................................. 5-19

Remote programming — dB ............................................. 5-20

6 Buffer

Buffer overview .......................................................................... 6-2

Front panel buffer ....................................................................... 6-2

Auto clear ............................................................................ 6-2

Timestamps ......................................................................... 6-4

Storing readings ................................................................... 6-6

Recalling readings ............................................................... 6-6

Buffer statistics .................................................................... 6-8

Remote programming — buffer ................................................. 6-9

Buffer commands ................................................................ 6-9

Programming example ...................................................... 6-15

7 Scanning

Scanning fundamentals ............................................................... 7-2

Channel assignments ........................................................... 7-3

Sequential and non-sequential scans ................................... 7-3

Scan process ........................................................................ 7-3

Trigger models .................................................................... 7-4

Scan configuration .................................................................... 7-11

Scan reset .......................................................................... 7-13

Simple scan ....................................................................... 7-13

Advanced scan .................................................................. 7-14

Setting delay ...................................................................... 7-18

Monitor channel ................................................................ 7-18

Auto channel configuration ............................................... 7-20

Saving setup ...................................................................... 7-21

Auto scan .......................................................................... 7-21

Scan operation .......................................................................... 7-22

Basic scan .......................................................................... 7-22

Manual/external trigger scan ............................................. 7-23

Monitor scan (analog trigger) ........................................... 7-24

Remote programming — scanning .......................................... 7-26

Trigger model .................................................................... 7-26

Channel setup .................................................................... 7-27

Buffer ................................................................................ 7-27

Scanning commands ......................................................... 7-27

Scanning programming example ...................................... 7-32

Scanning examples ................................................................... 7-33

External trigger scan ......................................................... 7-33

Monitor scan ..................................................................... 7-36

8 Triggering

Trigger model ............................................................................. 8-2

Idle ...................................................................................... 8-2

Control source and event detection ..................................... 8-3

Delay (auto or manual) ....................................................... 8-3

Device action ....................................................................... 8-5

Output trigger ...................................................................... 8-5

External triggering ..................................................................... 8-6

Digital I/O ........................................................................... 8-6

External trigger ................................................................... 8-7

Voltmeter complete ............................................................. 8-7

External triggering example ................................................ 8-8

External triggering with BNC connections ....................... 8-11

Remote programming — triggering ......................................... 8-12

Trigger model (remote operation) ..................................... 8-12

Trigger model operation .................................................... 8-14

Triggering commands ....................................................... 8-15

Programming example ...................................................... 8-16

9 Limits and Digital I/O

Limits .......................................................................................... 9-2

Scanning .............................................................................. 9-4

Basic limits operation .......................................................... 9-4

Digital I/O ................................................................................... 9-5

Digital input (trigger link input) .......................................... 9-5

Digital outputs ..................................................................... 9-6

Setting digital output ......................................................... 9-10

Scanning ............................................................................ 9-12

Remote programing — limits and digital output ...................... 9-12

Limits and digital output commands ................................. 9-12

Limits and digital outputs programming example ............ 9-14

Application — sorting resistors ................................................ 9-15

Limits ................................................................................ 9-15

Digital outputs ................................................................... 9-17

10 Remote Operations

Operation enhancements .......................................................... 10-2

Pseudocards ....................................................................... 10-2

Autozero ............................................................................ 10-2

dB calculation .................................................................... 10-2

Separate function setups .................................................... 10-2

DCV input divider ............................................................. 10-3

Multiple channel operation ................................................ 10-3

GPIB setup ................................................................................ 10-3

GPIB standards .................................................................. 10-3

Selecting GPIB and setting primary address ..................... 10-4

GPIB connections .............................................................. 10-4

General bus commands ............................................................. 10-7

REN (remote enable) ......................................................... 10-7

IFC (interface clear) .......................................................... 10-7

LLO (local lockout) ........................................................... 10-8

GTL (go to local) ............................................................... 10-8

DCL (device clear) ............................................................ 10-8

SDC (selective device clear) .............................................. 10-8

GET (group execute trigger) ............................................. 10-8

SPE, SPD (serial polling) .................................................. 10-9

Front panel GPIB operation ...................................................... 10-9

Error and status messages ................................................. 10-9

GPIB status indicators ....................................................... 10-9

LOCAL key ..................................................................... 10-10

Programming syntax .............................................................. 10-10

Command words ............................................................. 10-10

Query commands ............................................................ 10-12

Case sensitivity ............................................................... 10-12

Long-form and short-form versions ................................ 10-13

Short-form rules .............................................................. 10-13

Program messages ........................................................... 10-14

Response messages ......................................................... 10-16

Message exchange protocol ............................................ 10-16

RS-232 interface operation .................................................... 10-17

Sending and receiving data ............................................. 10-17

Baud rate ......................................................................... 10-17

Signal handshaking (flow control) .................................. 10-18

Terminator ....................................................................... 10-18

Selecting and configuring RS-232 interface ................... 10-19

RS-232 connections ........................................................ 10-19

Error messages ................................................................ 10-20

11 Status Structure

Overview .................................................................................. 11-2

Status byte and SRQ ......................................................... 11-2

Status register sets ............................................................. 11-2

Queues ............................................................................... 11-2

Clearing registers and queues ................................................... 11-4

Programming and reading registers ......................................... 11-5

Programming enable registers ........................................... 11-5

Reading registers ............................................................... 11-6

Status byte and service request (SRQ) ..................................... 11-6

Status byte register ............................................................ 11-7

Service request enable register .......................................... 11-7

Serial polling and SRQ ..................................................... 11-8

Status byte and service request commands ....................... 11-8

Serial poll programming example ..................................... 11-9

Status register sets .................................................................. 11-11

Register bit descriptions .................................................. 11-11

Condition registers .......................................................... 11-18

Event registers ................................................................. 11-18

Event enable registers ..................................................... 11-19

Queues .................................................................................... 11-22

Output queue ................................................................... 11-22

Error queue ...................................................................... 11-22

12 Common Commands

13 SCPI Signal Oriented Measurement Commands

CONFigure:<function> [<rang>], [<res>], [<clist>] .............. 13-4

FETCh? ..................................................................................... 13-6

READ? ..................................................................................... 13-7

MEASure:<function>? [<rang>], [<res>], [<clist>] ............... 13-8

14 FORMat and Miscellaneous SYSTem Commands

FORMat commands .................................................................. 14-2

FORMat[:DATA] <type>[,<length>] ............................... 14-2

FORMat:ELEMents <item list> ....................................... 14-6

FORMat:BORDer <name> .............................................. 14-7

Miscellaneous SYSTem commands ......................................... 14-8

SYSTem:PRESet ............................................................... 14-8

SYSTem:VERSion ............................................................ 14-8

SYSTem:KEY <NRf> ...................................................... 14-8

SYSTem:BEEPer[:STATe] <b> ....................................... 14-9

15 SCPI Reference Tables

Reference tables ........................................................................ 15-2

A Specifications

Accuracy calculations ................................................................ A-7

Calculating DC characteristics accuracy ............................ A-7

Calculating AC characteristics accuracy ............................ A-7

Calculating dBm characteristics accuracy .......................... A-8

Calculating dB characteristics accuracy ............................. A-8

Additional derating factors ................................................. A-9

Optimizing measurement accuracy ........................................... A-9

DC voltage, DC current, and resistance: ............................ A-9

AC voltage and AC current: ............................................... A-9

Temperature: ....................................................................... A-9

Optimizing measurement speed .............................................. A-10

DC voltage, DC current, and resistance: .......................... A-10

AC voltage and AC current: ............................................. A-10

Temperature: ..................................................................... A-10

B Model 7700 Connection Guide

Card configuration — schematic ............................................... B-2

Connections and wiring ............................................................ B-4

Screw terminals .................................................................. B-4

Wiring procedure ............................................................... B-6

Typical connections ........................................................... B-8

Connection log ................................................................. B-10

C Status and Error Messages

D Signal Processing Sequence and Data Flow

Signal processing sequence ....................................................... D-2

Basic signal processing ...................................................... D-2

Signal processing using instrument features ...................... D-3

Signal processing using Ratio or Ch Avg .......................... D-6

Data flow (remote operation) .................................................... D-7

SENSe and sample buffer .................................................. D-8

[SENS[1]]:DATA[LATest]? ............................................... D-9

[SENS[1]]:DATA:FRESh? ................................................. D-9

FETCh? ............................................................................ D-10

READ? ............................................................................. D-10

MEASure? ........................................................................ D-10

CALC[1]:DATA[LATest]? ............................................... D-10

CALC[1]:DATA:FRESh? ................................................ D-10

CALC3:LIM1:FAIL? ....................................................... D-11

CALC3:LIM2:FAIL? ....................................................... D-11

TRACe:DATA? ................................................................ D-11

CALC2:IMM? .................................................................. D-12

CALC2:IMM ................................................................... D-12

CALC2:DATA? ................................................................ D-12

Continuous measurement mode ....................................... D-12

Scanning ........................................................................... D-13

E Measurement Considerations

Measurement considerations ..................................................... E-2

Thermoelectric potentials ................................................... E-2

Thermoelectric generation .................................................. E-3

Minimizing thermal EMFs ................................................. E-4

Source resistance noise ....................................................... E-5

Magnetic fields ................................................................... E-6

Radio frequency interference ............................................. E-6

Ground loops ...................................................................... E-6

Shielding ............................................................................. E-8

Meter loading ..................................................................... E-9

F Temperature Equations

Thermocouple equation ............................................................. F-2

Thermistor equation ................................................................... F-6

RTD equations ........................................................................... F-8

G IEEE-488 Bus Overview

Introduction ............................................................................... G-2

Bus description .......................................................................... G-2

Bus lines .................................................................................... G-4

Data lines ............................................................................ G-4

Bus management lines ........................................................ G-4

Handshake lines .................................................................. G-5

Bus commands ........................................................................... G-6

Uniline commands .............................................................. G-8

Universal multiline commands ........................................... G-8

Addressed multiline commands ......................................... G-9

Address commands ............................................................ G-9

Unaddress commands ......................................................... G-9

Common commands ......................................................... G-10

SCPI commands ............................................................... G-10

Command codes ............................................................... G-10

Typical command sequences ............................................ G-12

IEEE command groups ..................................................... G-13

Interface function codes .......................................................... G-14

H KE2700 Instrument Driver Examples

Introduction ............................................................................... H-2

Visual Basic and CVI (C) examples .......................................... H-2

LabVIEW examples ................................................................ H-12

List of Illustrations

1 Getting Started

Figure 1-1 Model 2750 front panel ........................................................ 1-10

Figure 1-2 Model 2750 rear panel ......................................................... 1-14

Figure 1-3 Rack preparation .................................................................. 1-15

Figure 1-4 Power module ...................................................................... 1-17

Figure 1-5 Connection to DMM for 2-wire function

(system channel 101 closed) ............................................ 1-31

Figure 1-6 Connection to DMM for 4-wire function

(system channel 106 closed) ............................................ 1-32

Figure 1-7 Front panel keys to close and open system channels ........... 1-33

Figure 1-8 Simple scan operation .......................................................... 1-35

Figure 1-9 Exercise 4 — Trigger and return a single reading ............... 1-38

Figure 1-10 Exercise 5 — Trigger and return multiple readings ............. 1-39

Figure 1-11 Exercise 6 — Return a single reading

(continuous triggering) .................................................... 1-40

2 Closing and Opening Switching Module Channels

Figure 2-1 2-wire system channel connections to Model 2750 DMM .... 2-7

Figure 2-2 4-wire system channel connections to Model 2750 DMM .... 2-8

Figure 2-3 System channel operation — closing next or previous

measurement channel ........................................................ 2-9

Figure 2-4 System channel operation — specifying measurement

channel to close ............................................................... 2-10

Figure 2-5 System channel operation — opening all channels

in mainframe .................................................................... 2-11

Figure 2-6 Multiple channel operation — specifying a channel

to close ............................................................................. 2-18

Figure 2-7 Multiple channel operation — opening one or all

channels ........................................................................... 2-19

Figure 2-8 Dual multiplexer configuration (Model 7700) ..................... 2-24

Figure 2-9 Dual multiplexer application connections ........................... 2-26

Figure 2-10 Testing DUT 1 ..................................................................... 2-27

Figure 2-11 CARD menu tree ................................................................. 2-31

Figure 2-12 Model 7700 simplified schematic ........................................ 2-37

3 Basic DMM Operation

Figure 3-1 Line cycle synchronization .................................................... 3-5

Figure 3-2 DCV and ACV connections using front panel inputs ............ 3-9

Figure 3-3 DCV and ACV connections using Model 7700 switching

module ............................................................................. 3-10

Figure 3-4 ACV measurements – sine waves ........................................ 3-13

Figure 3-5 ACV measurements – square, pulse, and sawtooth waves ... 3-14

Figure 3-6 DCI and ACI connections using front panel inputs .............. 3-17

Figure 3-7 DCI and ACI connections using Model 7700 switching

module ............................................................................. 3-17

Figure 3-8
Figure 3-9

Figure 3-10 Constant-current method to measure ohms

Figure 3-11 Ratiometric method to measure ohms

Figure 3-12 Open ohms test lead detection .............................................. 3-33

Figure 3-13 Open Sense Lo lead detection (10MΩ and

Figure 3-14 Thermocouple connections .................................................. 3-40

Figure 3-15 Thermistor connections ........................................................ 3-42

Figure 3-16 4-wire RTD connections ...................................................... 3-43

Figure 3-17 FREQ and PERIOD connections for front panel inputs ...... 3-48

Figure 3-18 FREQ and PERIOD connections using Model 7700

Figure 3-19 Continuity connections ......................................................... 3-51

Ω

2 and Ω4 connections for front panel inputs ..................... 3-21

Ω

2 and Ω4 connections for Model 7700 switching

module ............................................................................. 3-22

(1Ω to 1MΩ ranges) ......................................................... 3-29

(10MΩ and 100MΩ ranges) ............................................ 3-31

100MΩ ranges) ................................................................ 3-34

switching module ............................................................. 3-49

4 Range, Digits, Rate, Bandwidth, and Filter

Figure 4-1 Speed vs. noise characteristics ............................................... 4-8

Figure 4-2 Moving and repeating filters ................................................ 4-15

Figure 4-3 Filter window ....................................................................... 4-17

Figure 4-4 Filter configuration flow chart .............................................. 4-19

5 Relative, Math, Ratio, Channel Average, and dB

Figure 5-1 MATH menu tree .................................................................... 5-7

6 Buffer

Figure 6-1 Recalling buffer data — relative timestamp ........................... 6-7

Figure 6-2 Recalling buffer data — real-time clock timestamp .............. 6-7

7 Scanning

Figure 7-1 Trigger model with STEP function ........................................ 7-5

Figure 7-2 Trigger model with SCAN function ....................................... 7-6

Figure 7-3 Scan configuration flowchart ................................................ 7-11

Figure 7-4 External trigger scan example .............................................. 7-34

Figure 7-5 Monitor scan example .......................................................... 7-37

8 Triggering

Figure 8-1 Front panel trigger model (without scanning) ....................... 8-2

Figure 8-2 Device action ......................................................................... 8-5

Figure 8-3 TRIG LINK pinout ................................................................ 8-6

Figure 8-4 Trigger link input pulse specifications (EXT TRIG) ............. 8-7

Figure 8-5 Trigger link output pulse specifications (VMC) .................... 8-7

Figure 8-6 DUT test system .................................................................... 8-8

Figure 8-7 Trigger link connections ........................................................ 8-9

Figure 8-8 Operation model for triggering example ............................. 8-10

Figure 8-9 DIN to BNC trigger cable .................................................... 8-11

Figure 8-10 Trigger model (remote operation) ........................................ 8-13

9 Limits and Digital I/O

Figure 9-1 Default limits ......................................................................... 9-2

Figure 9-2 Digital I/O port ...................................................................... 9-5

Figure 9-3 Digital I/O port simplified schematic ..................................... 9-6

Figure 9-4 Controlling externally powered relays ................................... 9-9

Figure 9-5 NAND gate control .............................................................. 9-10

Figure 9-6 Setup to test 100Ω resistors ................................................. 9-15

Figure 9-7 Limits to sort 100Ω resistors (1%, 5%, and >5%) ............... 9-16

10 Remote Operations

Figure 10-1 IEEE-488 connector ............................................................. 10-4

Figure 10-2 IEEE-488 connections ......................................................... 10-5

Figure 10-3 IEEE-488 connector location ............................................... 10-6

Figure 10-4 RS-232 interface connector ............................................... 10-19

11 Status Structure

Figure 11-1 Model 2750 status register structure .................................... 11-3

Figure 11-2 16-bit status register ............................................................. 11-5

Figure 11-3 Status byte and service request (SRQ) ................................. 11-6

Figure 11-4 Standard event status .......................................................... 11-11

Figure 11-5 Operation event status ........................................................ 11-13

Figure 11-6 Measurement event status .................................................. 11-15

Figure 11-7 Questionable event status ................................................... 11-17

14 FORMat and Miscellaneous SYSTem Commands

Figure 14-1 ASCII data format ................................................................ 14-3

Figure 14-2 IEEE-754 data formats ......................................................... 14-5

Figure 14-3 Key-press codes ................................................................... 14-9

B Model 7700 Connection Guide

Figure B-1 Simplified schematic for Model 7700 ................................... B-3

Figure B-2 Screw terminal access ........................................................... B-5

Figure B-3 Model 7700 screw terminal channel designations ................ B-5

Figure B-4 Wire dressing ......................................................................... B-7

Figure B-5 Thermocouple connections ................................................... B-8

Figure B-6
Figure B-7

Figure B-8 Current connections (AC or DC) ........................................... B-9

Figure B-9 Voltage connections (DC or AC) ......................................... B-10

Ω

2-Wire and thermistor connections .................................... B-8

Ω

4-Wire and RTD connections ............................................. B-9

D Signal Processing Sequence and Data Flow

Figure D-1 Basic signal processing ......................................................... D-2

Figure D-2 Signal processing using instrument features ......................... D-3

Figure D-3 Signal processing using Ratio or Channel Average .............. D-6

Figure D-4 Data flow for remote operation ............................................. D-7

E Measurement Considerations

Figure E-1 Thermal EMF generation ...................................................... E-3

Figure E-2 Power line ground loops ........................................................ E-7

Figure E-3 Eliminating ground loops ...................................................... E-7

Figure E-4 Shielding example ................................................................. E-8

Figure E-5 Meter loading ........................................................................ E-9

G IEEE-488 Bus Overview

Figure G-1 IEEE-488 bus configuration .................................................. G-3

Figure G-2 IEEE-488 handshake sequence ............................................. G-5

Figure G-3 Command codes .................................................................. G-11

List of Tables

1 Getting Started

Table 1-1 Model 77xx series switching modules ................................... 1-8

Table 1-2 Fuse ratings .......................................................................... 1-18

Table 1-3 Display commands ............................................................... 1-20

Table 1-4 Default settings .................................................................... 1-23

Table 1-5 Default setup commands ...................................................... 1-26

Table 1-6 Exercise 1 — Measure AC volts - store readings in buffer .. 1-30
Table 1-7 Exercise 2 — Close and open channels (system channel

Table 1-8 Exercise 3 — Simple scanning ............................................ 1-36

2 Closing and Opening Switching Module Channels

Table 2-1 System channel control commands ...................................... 2-12

Table 2-2 Multiple channel control commands .................................... 2-20

Table 2-3 Relay closure count commands ........................................... 2-33

3 Basic DMM Operation

Table 3-1 Autozero and LSYNC commands ......................................... 3-6

Table 3-2 Color codes — thermocouple wires ..................................... 3-41

Table 3-3 Thermocouple temperature measurement configuration ..... 3-44

Table 3-4 Thermistor temperature measurement configuration ........... 3-45

Table 3-5 RTD parameters ................................................................... 3-45

Table 3-6 4-wire RTD temperature measurement configuration ......... 3-46

Table 3-7 Basic measurement commands ............................................ 3-52

operation) ......................................................................... 1-34

4 Range, Digits, Rate, Bandwidth, and Filter

Table 4-1 Measurement ranges and maximum readings ........................ 4-2

Table 4-2 Range commands ................................................................... 4-4

Table 4-3 Digits commands ................................................................... 4-6

Table 4-4 Rate and bandwidth settings .................................................. 4-9

Table 4-5 Rate and bandwidth commands ........................................... 4-11

Table 4-6 Filter commands .................................................................. 4-20

5 Relative, Math, Ratio, Channel Average, and dB

Table 5-1 Rel commands ....................................................................... 5-4

Table 5-2 Math commands ................................................................... 5-12

Table 5-3 Ratio and channel average commands ................................. 5-17

Table 5-4 dB commands ...................................................................... 5-20

6 Buffer

Table 6-1 Buffer commands ................................................................... 6-9

7 Scanning

Table 7-1 Scanning commands ............................................................. 7-28

Table 7-2 External trigger scan example .............................................. 7-35

Table 7-3 Monitor scan example .......................................................... 7-38

8 Triggering

Table 8-1 Auto delay settings ................................................................. 8-4

Table 8-2 SCPI commands — triggering ............................................. 8-15

9 Limits and Digital I/O

Table 9-1 OUTPUT menu .................................................................... 9-11

Table 9-2 Limits and digital I/O commands ......................................... 9-12

10 Remote Operations

Table 10-1 General bus commands ........................................................ 10-7

Table 10-2 RS-232 connector pinout .................................................... 10-20

Table 10-3 PC serial port pinout ........................................................... 10-20

11 Status Structure

Table 11-1 Common and SCPI commands to reset registers and

clear queues ...................................................................... 11-4

Table 11-2 Status byte and service request enable register commands .. 11-9

Table 11-3 Condition register commands ............................................. 11-18

Table 11-4 Event register commands ................................................... 11-18

Table 11-5 Event enable registers commands ...................................... 11-19

Table 11-6 Error queue commands ...................................................... 11-23

12 Common Commands

Table 12-1 IEEE-488.2 common commands and queries ...................... 12-2

13 SCPI Signal Oriented Measurement Commands

Table 13-1 Signal oriented measurement command summary .............. 13-2

14 FORMat and Miscellaneous SYSTem Commands

Table 14-1 SCPI commands — data format ........................................... 14-2

15 SCPI Reference Tables

Table 15-1 CALCulate command summary .......................................... 15-3

Table 15-2 DISPlay command summary ............................................... 15-6

Table 15-3 FORMat command summary ............................................... 15-6

Table 15-4 ROUTe command summary ................................................. 15-7

Table 15-5 SENSe command summary ................................................. 15-8

Table 15-6 STATus command summary .............................................. 15-19

Table 15-7 SYSTem command summary ............................................ 15-20

Table 15-8 TRACe command summary .............................................. 15-24

Table 15-9 Trigger command summary ............................................... 15-25

Table 15-10 UNIT command summary ................................................. 15-26

B Model 7700 Connection Guide

Table B-1 Connection log Model 7700 ............................................... B-11

C Status and Error Messages

Table C-1 Status and error messages ..................................................... C-2

E Measurement Considerations

Table E-1 Material thermoelectric coefficients ...................................... E-2

F Temperature Equations

Table F-1 Type B inverse function polynomial ...................................... F-2

Table F-2 Type E inverse function polynomial ...................................... F-3

Table F-3 Type J inverse function polynomial ....................................... F-3

Table F-4 Type K inverse function polynomial ...................................... F-4

Table F-5 Type N inverse function polynomial ...................................... F-4

Table F-6 Type R inverse function polynomial ...................................... F-5

Table F-7 Type S inverse function polynomial ...................................... F-5

Table F-8 Type T inverse function polynomial ...................................... F-6

Table F-9 Model 2750 curve fitting constants for thermistors ............... F-6

Table F-10 RTD parameters ..................................................................... F-8

G IEEE-488 Bus Overview

Table G-1 IEEE-488 bus command summary ........................................ G-7

Table G-2 Hexadecimal and decimal command codes ........................ G-10

Table G-3 Typical addressed command sequence ................................ G-12

Table G-4 Typical addressed command sequence ................................ G-12

Table G-5 IEEE command groups ....................................................... G-13

Table G-6 Model 2750 interface function codes .................................. G-14

H KE2700 Instrument Driver Examples

Table H-1 Visual Basic and CVI (C) examples ...................................... H-3

Table H-2 LabVIEW examples ............................................................ H-12

1

Getting Started

Quick Start

acquaint yourself with fundamental instrument operations. Use
yourself with front panel controls, use

QS3

QS1 •

QS2 •

— Of the following section topics, three can be used immediately to quickly

QS1

to familiarize

QS2

to power-up the instrument, and, finally, use

to perform exercises to operate the instrument.

•

General information

information, contact information, safety symbols and terms, inspection, and
available options and accessories.

•

Model 2750 features

•

Plug-in switching modules

Model 77XX series switching modules.

Front and rear panel familiarization

of the instrument.

•

Rack mounting

in a standard 19-inch rack.

Power-up

power line frequency, and the power-up sequence.

•

Display

•

Defaults and user setups

covers the three setup configurations available to the user.

— Covers line power connection, line voltage setting, fuse replacement,

— Provides information about the display of the Model 2750.

— Covers general information that includes warranty

— Summarizes the features of Model 2750.

— Summarizes the capabilities of the Keithley

— Summarizes the controls and connectors

— Covers the options available for rack mounting the Model 2750

— Lists the *RST and factory default settings, and

QS3 •

•

Remote programming information

presented in this manual.

Quick start exercises

(front panel and remote programming) to acquaint a user with operation basics.

— Provides abbreviated operating information and exercises

— Explains how SCPI commands are

1-2 Getting Started Model 2750 Multimeter/Switch System User’s Manual

General information

Warranty information

Warranty information is located at the front of this manual. Should your Model 2750
require warranty service, contact the Keithley representative or authorized repair facility in
your area for further information. When returning the instrument for repair, be sure to fill
out and include the service form at the back of this manual to provide the repair facility
with the necessary information.

NOTE

The service form requires the serial number of the Model 2750. The serial

number is located on the rear panel. It can also be read from the front panel by

selecting the SNUM item of the SETUP menu. Press SHIFT and then SETUP to

access the menu. For remote operation, the serial number can be read using the

*IDN? command (see Section 12 for details).

Contact information

Worldwide phone numbers are listed at the front of this manual. If you have any questions,
please contact your local Keithley representative or call a Keithley Application Engineer at
1-800-348-3735 (U.S. and Canada only).

Safety symbols and terms

The following symbols and terms may be found on the instrument or used in this manual:

!

The symbol on an instrument indicates that the user should refer to the operating
instructions located in the manual.

The symbol on the instrument shows that high voltage may be present on the
terminal(s). Use standard safety precautions to avoid personal contact with these voltages.

The

WARNING

personal injury or death. Always read the associated information very carefully before
performing the indicated procedure.

heading used in this manual explains dangers that might result in

The

CAUTION

instrument. Such damage may invalidate the warranty.

heading used in this manual explains hazards that could damage the

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-3

Inspection

Model 2750 was carefully inspected electrically and mechanically before shipment. After
unpacking all items from the shipping carton, check for any obvious signs of physical
damage that may have occurred during transit. (There may be a protective film over the
display lens, which can be removed). Report any damage to the shipping agent
immediately. Save the original packing carton for possible future shipment. The following
items are included with every Model 2750 order:

• Model 2750 with line cord.

• Safety test leads (Model 1751).

• Accessories as ordered.

• Hardware for rack mounting.

• Certificate of calibration.

• Model 2750 User’s Manual (P/N 2750-900-00).

• Manual Addenda (pertains to any improvements or changes concerning the
instrument or manual).

• Software CD containing the following:

• TestPoint Runtime – Provides basic data logging capabilities. This can be
modified with the TestPoint application development package (optional
software).

• KE2700 IVI Instrument Driver – Provided for programmers, designed for use
with application development environments.

Optional “Software” available from Keithley is summarized on page 1-6.

If an additional manual is required, order the appropriate manual package. The manual
packages include a manual and any pertinent addenda.

Options and accessories

Plug-in switching modules

NOTE Table 1-1 provides a side-by-side comparison of the following Keithley

switching modules. All multiplexer modules can be configured as two
independent multiplexers.

NOTE The Model 77XX Series Switching Modules Instruction Manual provides

operating and service information for the switching modules. This manual is
supplied with each switching module.

Model 7700 — This differential multiplexer provides 20 channels of 2-pole input, or 10
channels of 4-pole input. The internal cold junction allows direct-connection of
thermocouples. It also has two 2-pole channels used exclusively for current input.

1-4 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Model 7701 — This differential multiplexer provides 32 channels of 2-pole input, or
16 channels of 4-pole input.

Model 7702 — This differential multiplexer provides 40 channels of 2-pole input, or
20 channels of 4-pole input. It also has two 2-pole channels used exclusively for current
input.

Model 7703 — This differential multiplexer provides 32 channels of 2-pole input, or
16 channels of 4-pole input.

Model 7705 — This control module provides 40 independent 1-pole switching (SPST)
channels that are isolated from the internal DMM.

Model 7706 — This all-in-one module provides 20/10 channels of 2/4-pole input,
16 digital outputs, two analog outputs, one 32-bit counter with gating and totalizer.

Model 7707 — This module provides 10 channels of 2-pole input, or 5 channels of 4-pole
input. Also provides 32 digital inputs/outputs.

Model 7708 — This differential multiplexer provides 40 channels of 2-pole input, or 20
channels of 4-pole input. The internal cold junction allows direct-connection of
thermocouples for temperature measurements.

Model 7709 — This module is configured as a 6 × 8 matrix (six rows, eight columns). The
matrix consists of 48 crosspoint channels and two backplane isolation channels. For
system channel operation, row 1 is connected to DMM Input. For 4-wire measurements,
row 2 is connected to DMM Sense.

Model 7710 — This differential multiplexer provides 20 channels of 2-pole input or
10 channels of 4-pole input. The internal cold junction allows direct-connection of
thermocouples for temperature measurements. This module provides high-speed
switching and uses long-life relays.

Model 7711 — The Model 7711 is a 50Ω, 2GHz, single-pole dual 1 × 4 RF Multiplexer
module (eight channels, no measurement capability). This 1 × 4 multiplexer is a cascading
tree design — one of the channels of each is always connected to a common out. It can be
used to connect one instrument to multiple devices or multiple instruments to a single
device.

Model 7712 — The Model 7712 is a 50Ω, 3.5GHz, single-pole dual 1 × 4 RF Multiplexer
module (eight channels, no measurement capability). This 1 × 4 multiplexer is a cascading
tree design — one of the channels of each is always connected to a common out. It can be
used to connect one instrument to multiple devices or multiple instruments to a single
device.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-5

Cables and connector kits for switching modules

Model 7788 DB-50 connector kit — Contains two male DB-50 solder cup connectors
with strain relief connector shells. These connectors mate to the female connectors of the
Models 7703 and 7705 switching modules.

Model 7789 50/25-pin solder cup connector kit — Contains one male DB-50 and one
male DB-25 solder cup connectors. These connectors mate to the female connectors on the
Models 7701 and 7709 switching modules.

Model 7790 ribbon cable adapter kit — Contains one female DB-50, one male DB-50
and one male DB-25 IDC ribbon cable connectors. These connectors are used with the
Models 7701, 7707 and 7709 switching modules.

Model 7051-X — BNC cable (male to male). 7051-2 is 2 ft long, 7051-5 is 5 ft long, and
7051-10 is 10 ft long. These cable are used with the Model 7711 switching module.

Model 7712-SMA-1 — SMA cable (male to male), 1.0m (3.3 ft) long. This cable is used
with the Models 7711 and 7712 switching modules.

Model 7712-SMA-N — Female SMA to male N-type adapter. This adapter is used with
the Models 7711 and 7712 switching modules.

S46-SMA-X — SMA cable (male to male). S46-SMA-1 is one foot long and
S46-SMA-0.5 is one-half foot long. This cable is used with the Models 7711 and 7712
switching modules.

Cables and adapters (GPIB and trigger link)

Models 7007-1 and 7007-2 shielded GPIB cables — Connect Model 2750 to the GPIB
bus using shielded cables and connectors to reduce electromagnetic interference (EMI).
Model 7007-1 is one meter long; Model 7007-2 is two meters long.

Models 8501-1 and 8501-2 trigger link cables — Connect Model 2750 to other
instruments with Trigger Link connectors (e.g., Model 7002 Switch System).
Model 8501-1 is one meter long; Model 8501-2 is two meters long.

Model 8502 trigger link adapter — Lets you connect any of the six trigger link lines of
Model 2750 to instruments that use the standard BNC trigger connectors.

Model 8503 DIN to BNC trigger cable — Lets you connect trigger link lines one
(Voltmeter Complete) and two (External Trigger) of Model 2750 to instruments that use
BNC trigger connectors. Model 8503 is one meter long.

1-6 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Software

The following optional software is available from Keithley:

ExceLINX-1A – This is an economical, easy-to-use, add-in utility for Microsoft Excel ®
and Keithley Integra Series Multimeter/Switch systems. No programming is required —
configure your measurements quickly using pop-up menus and eliminate time-consuming
and error prone programming. Acquire data into a spreadsheet on the fly during a scan or
transfer data into a spreadsheet after a scan is completed. A few mouse clicks are all it
takes to configure channels, set parameters, triggers, and scan lists. There is no need to
launch a separate data logging or data-crunching application; live data streams
automatically into an Excel workbook, ready for analysis or charting using all of Excel's
powerful built-in tools.

TestPoint application development package — This powerful and economical
programming environment uses object-oriented technology through a drag-and-drop
interface to build a basic system quickly and without in-depth programming. Optional
toolkits (database and statistical process control) are available to expand ExceLINX-1A
capability.

Rack mount kit

Model 4288-7 rack mount kit — Mounts a Model 2750 in a standard 19-inch rack.
Includes rear brackets to provide additional support for a mainframe that has two or more
switching modules installed.

NOTE The Model 2750 includes hardware that allows it to be mounted to the front rails

of a standard 19-inch rack. With two or more switching modules installed, rear
support brackets may be required. The Model 4288-7 rack mount kit includes
rear support brackets.

Model 2750 features

Model 2750 is a 6½-digit high-performance multimeter/data acquisition system. It can
measure voltage (DC and AC), current (DC and AC), resistance (2- and 4-wire),
temperature (thermocouple, thermistor, and 4-wire RTD), frequency and period, and test
continuity.

The Model 2750 has five slots that will accommodate Keithley Model 7700 series
switching modules (Table 1-1). Each channel of a switching module that is closed or
scanned is measured by the Model 2750. For scanning, each channel can have its own
unique setup (i.e., function, range, digits, etc.).

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-7

More information on the measurement capabilities of the Model 2750 is provided in

“DMM measurement capabilities,” page 3-2. A connection guide for the Model 7700 is

provided in Appendix B. Specifications for the Model 2750 and 7700 switching module
are provided in Appendix A.

Additional features of Model 2750 include:

• Setup storage — Five instrument setups (three user, *RST defaults and factory
defaults) can be saved and recalled.

• Offset compensated ohms — A two-measurement process for 4-wire ohms to
cancel the effects of thermal EMFs. Available for the 1Ω, 10Ω, 100Ω, 1kΩ, and
10kΩ, ranges.

• Dry circuit ohms — Low voltage mode (20mV open-circuit clamping) for 4-wire
ohms measurements. Available for the 1Ω, 10Ω, 100Ω, and 1kΩ ranges.

• Math — mX+b, percent, and reciprocal (1/X) calculations provide mathematical
manipulation of readings.

• Relative — Null offsets or establish baseline values.

• Ratio and channel average — Ratio and average calculations for two switching
module channels.

• Buffer — Store up to 110,000 readings in the internal buffer.

• Limits — Two sets of high and low reading limits to test devices.

• Digital I/O port — Five digital limit test output lines to control external circuitry.
The digital trigger link and hardware interlock input can also be accessed at this
port.

• Monitor — The Model 2750 can monitor a selected channel. A scan can be
triggered to start when the Monitor detects a reached reading limit.

• Remote interface — Model 2750 can be controlled using the IEEE-488 interface
(GPIB) or the RS-232 interface.

Plug-in switching modules

Up to five Keithley Model 77XX series switching modules can be installed in the
Model 2750. A side-by-side comparison of the switching modules is provided in

Table 1-1.

Basic close/open operation for switching module channels is provided in Section 2,
while scanning is covered in Section 7. Connection information for the Model 7700
switching module is provided in Appendix B. For all other switching modules,
connection information is provided in the packing list that was shipped with each
switching module.

1-8 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Table 1-1

Model 77xx series switching modules

Model 7700 Model 7701 Model 7702 Model 7703

2-pole Operation 20 channels 32 channels 40 channels 32 channels
4-pole Operation 10 channel pairs 16 channel pairs 20 channel pairs 16 channel pairs
1-pole Operation N/A N/A N/A N/A
Measure Volts 300V maximum 150V maximum 300V maximum 300V maximum
Measure Amps Ch 21 & 22, 3A Max No Ch 41 & 42, 3A Max No
Measure Ohms 2/4-wire 2/4-wire 2/4-wire 2/4-wire
Thermocouple

YesNoNoNo

Cold Junction
Relay Type

1

Connector type Oversized screw

Configuration
Unique features All DMM functions All DMM functions

Latching electro­mechanical

terminals

2

Multiplexer Multiplexer Multiplexer Multiplexer

Latching electro­mechanical

1 female DB-50
1 female DB-25

Latching electro­mechanical

Oversized screw
terminals

All DMM functions All DMM functions

except amps

Non-latching reed

2 female DB-50s

except amps

Model 7705 Model 7706 Model 7707 Model 7708

2-pole Operation N/A 20 channels 10 channels 40 channels
4-pole Operation N/A 10 channel pairs 5 channel pairs 20 channel pairs
1-pole Operation 40 channels N/A N/A N/A
Measure Volts 300V maximum 300V maximum 300V 300V maximum
Measure Amps No No No No
Measure Ohms No 2/4-wire 2/4-wire 2/4-wire
Thermocouple

No Yes No Yes

Cold Junction
Relay Type

1

Connector type 2 female DB-50s Mini screw terminal 1 male DB-50

Configuration

Latching electro­mechanical

2

Independent SPST

Latching electro­mechanical

Latching electro­mechanical

Latching electro­mechanical

Oversized screw

1female DB-25

terminals

Multiplexer Multiplexer Multiplexer

channels

Unique features Multiple channel

operation only

16 digital outputs, 2
analog outputs, one

32 digital inputs/
outputs

All DMM functions
except amps

counter/totalizer

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-9

Table 1-1 (continued)

Model 77xx series switching modules

Models 7711

Model 7709 Model 7710

and 7712

2-pole Operation 8-channels 20 channels N/A
4-pole Operation 4 channel pairs 10 channel pairs N/A
1-pole Operation N/A N/A 8 channels
Measure Volts 300V maximum 60V maximum No

3

Measure Amps No No No3

3

Measure Ohms 2/4-wire 2/4-wire No
Thermocouple

No Yes No

3

Cold Junction
Relay Type

Connector type 1 female DB-50

Configuration
Unique features Rows 1 & 2 connect

1

Latching electro­mechanical

Solid state
opto-coupled FET

3.5mm removable

1 female DB-25

2

6 x 8 matrix Multiplexer Multiplexer

screw terminals

High-speed switching

to DMM (system

and long-life relays

High frequency
electromechanical

10 SMA

50Ω RF dual 1 x 4
multiplexer

channel operation)

Max Frequency:
7711: 2GHz
7712: 3.5GHz

1. Latching relays hold their open/close state after the mainframe is turned off. When turned on, all relays open after a few
seconds.

2. All multiplexers can be configured as two independent multiplexers

3. The Models 7711 and 7712 have no measurement capabilities.

Pseudocards

Using remote programming, you can assign a pseudocard to an empty switching module
slot. With a pseudocard “installed,” the Model 2750 will operate as if the switching
module is installed in the Model 2750. This feature allows you to configure your system
without having the actual switching module installed in the unit. There is a pseudocard for
every Keithley Model 77xx series switching module. For details, see “Pseudocards,”

page 2-5.

1-10 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Identifying installed switching modules

On power-up, the model numbers of installed switching modules are displayed briefly.
While in the normal display state, slot indicators on the right side of the display indicate
which slots have a switching module or pseudocard installed.

NOTE If a Model 7700, 7701, 7702, 7703, 7705, 7708, 7709, 7710, 7711, or 7712

switching module is removed while the Model 2750 is on, the slot indicator for
that slot will remain on and the instrument will operate as if the module is
installed. That is, the Model 2750 will operate as if the pseudocard is installed.

If a Model 7706 or 7707 is removed while power is on, error +523 “Card hard­ware error” will occur, and the module will be removed from the system.

In general, it is not recommended to install or remove switching modules with
the power on.

The CARD menu and remote query commands can be used to identify modules installed
in the mainframe. For details, see “Switching module installation and connections,”

page 2-3.

Front and rear panel familiarization

Front panel summary

The front panel of Model 2750 is shown in Figure 1-1.

Figure 1-1

Model 2750 front panel

5

SLOT 1

TEMP

RANGE

AUTO

RANGE

SLOT 2

SLOT 3

SLOT 4

SLOT 5

MODEL 2750 MULTIMETER/SWITCH SYSTEM

INTEGRA SERIES

3

4

CONT

CH AVG

DCIACV

LIMITS ON/OFFDELAY

RECALL

CONFIG HALT

STEP SCAN

ACIΩ2Ω4

TYPE

TEST

DIGITS RATE

OCOMP

MONITOR

LSYNC

RELFILTER

PERIOD SENSOR

FREQ

CH-OFF CARD

RS-232

GPIB

EXIT ENTER

RATIO

MATH

OUTPUT

SHIFT

DCV

DRYCKT

LOCAL

EX TRIG

TRIG

1

POWER

SAVE SETUP

OPEN

STORE

CLOSE

2

350V
PEAK

SENSE

Ω 4 WIRE

INPUT

F

FRONT/REAR

CAT I

INPUT

HI

1000V

!

PEAK

LO

500V

PEAK

R

AMPS

3A, 250V

7

6

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-11

NOTE Most keys provide a dual function or operation. The nomenclature on a key

indicates its unshifted function/operation, which is selected by pressing the key.
Nomenclature (in blue) above a key indicates its shifted function. A shifted
function is selected by pressing the SHIFT key and then the function/operation
key.

1 Special keys and power switch:

SHIFT Use to select a shifted function or operation.
LOCAL Cancels GPIB remote mode.
POWER Power switch. In position turns 2750 on (I), out position turns it off (O).

2 Function and operation keys:

Top Row

Unshifted
DCV Selects DC voltage measurement function.
ACV Selects AC voltage measurement function.
DCI Selects DC current measurement function.
ACI Selects AC current measurement function.

Ω2 Selects 2-wire resistance measurement function.
Ω4 Selects 4-wire resistance measurement function.

FREQ Selects frequency measurement function.
TEMP Selects temperature measurement function.

Shifted
MATH Configures and controls mX+b, percent, or reciprocal (1/X) calculation.
OUTPUT Configures and controls digital and audio (beeper) output for limits.
RATIO Enables/disables channel ratio.
CH-AVG Enables/disables channel average.
CONT Configures and controls continuity test.
OCOMP Enables/disables offset compensated ohms with Ω4 function selected.
PERIOD Selects period measurement function.
SENSOR Configures temperature measurements.

Middle Row

Unshifted
EXTRIG Selects external triggering (front panel, bus, trigger link) as the trigger source.
TRIG Triggers a measurement when in external triggering (EX TRIG).
STORE Sets the number of readings to store and enables the buffer.
RECALL Displays stored readings and buffer statistics. Use the , , , and  keys to navigate

through buffer.
FILTER Enables/disables filter for selected function.
REL Enables/disables relative for selected function.

 and  Dual function — Manually scans switching channels. When in a menu, these keys

control cursor position for making selections or change values.

1-12 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Shifted
DELAY Sets user delay between trigger and measurement.
DRYCKT Selects dry circuit ohms (Ω4 must first be selected).
LIMITS Sets upper and lower limits for readings.
ON/OFF Enables/disables limits.
TYPE Configures and enables filter for selected function.
MONITOR Selects and enable/disables monitor channel.
CH-OFF Disables channel for a scan (must be in scan channel setup mode).
CARD Identifies switching modules installed in mainframe. Set up switching modules that

require configuration. View closed channels and channel settings for switching
modules that require configuration.

Bottom Row

Unshifted
OPEN Opens closed channel.
CLOSE Closes specified channel.
STEP Steps through channels; sends a trigger after each channel.
SCAN Scans through channels; sends a trigger after last channel.
DIGITS Sets display resolution for all functions.
RATE Sets measurement speed (fast, medium, or slow) for all functions.
EXIT Cancels selection, moves back to measurement display.
ENTER Accepts selection, moves to next choice or back to measurement display.
Shifted
SAVE Saves up to three instrument setups for future recall, and selects power-on setup.
SETUP Restores a default setup (factory or *RST) or a saved setup. Enables/disables buffer

auto clear, auto scan, and auto channel configuration. Sets timestamp, date, and

time. Displays serial number of Model 2750.
CONFIG Selects and configures a simple scan or an advanced scan.
HALT Disables step/scan.
TEST Selects the calibration menu, display test or the key-press test.
LSYNC Enables/disables line cycle synchronization. When enabled, noise induced by the

power line is reduced at the expense of speed.
GPIB Enables/disables GPIB and selects address.
RS-232 Enables/disables RS-232 interface; selects baud rate, flow control, and terminator.

3 Range keys:

 and  Dual function — Selects the next higher/lower measurement range for the selected

function. When in a menu, these keys make selections or change values.
AUTO Enables/disables autorange for the selected function.

4 Display annunciators:

* (asterisk) Readings being stored in buffer.
↔ (more) Indicates additional selections are available.
))) (speaker) Beeper on for continuity or limits testing.

Digital input/output or analog output active (set to non-default value).
4W 4-wire resistance or 4-wire RTD temperature reading displayed.
DCKT Dry circuit resistance reading displayed.
~AC AC function selected (ACV, dB, or ACI).
AUTO Auto range enabled.
BUFFER Recalling readings stored in buffer.
CHAN Setup or a reading for a switching channel displayed.
DELTA Channel average enabled.
ERR Questionable reading, or invalid cal step.
FAST Fast reading rate selected.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-13

FILT Filter enabled for selected function.
HIGH Reading has reached or exceeded the enabled high limit.
LSTN Instrument addressed to listen over GPIB.
LOW Reading has reached or exceeded the enabled low limit.
MATH mX+b, percent, or reciprocal (1/X) calculation enabled.
MED Medium reading rate selected.
MON Monitor channel displayed.
OCOMP 4-wire offset compensated ohms enabled.
RATIO Channel ratio enabled.
REAR Front panel input terminals disconnected.
REL Relative enabled for selected function.
REM Instrument in GPIB remote mode.
SCAN Scanning operation being performed.
SHIFT Accessing a shifted key.
SLOW Slow reading rate selected.
SRQ Service request over GPIB.
STAT Displaying buffer statistics.
STEP Stepping operation being performed.
TALK Instrument addressed to talk over GPIB bus.
TIMER Timer controlled triggering in use.
TRIG External triggering selected (trigger link, TRIG key, or GPIB).

5 Slot indicators:

Lit lamp indicates that the slot has a switching module or pseudocard installed in it. When the VIEW
option of the CARD menu is used, only the lamp that corresponds to the selected slot is turned on.

6 INPUTS switch:

Use to select front panel inputs (out; F) position, or switching module inputs (in; R) position.

NOTE For remote programming, the following command queries the INPUTS switch

position:

SYSTem:FRSWitch? ' Query INPUTS switch; 0 = rear, 1 = front.

7 Front panel inputs:

INPUT HI and LO Used for DCV, ACV, Ω2, CONT, FREQ, PERIOD, and thermocouple/thermistor

TEMP measurements.

SENSE HI and LO Use with INPUT HI and LO for Ω4 and RTD TEMP measurements.
AMPS Use with INPUT LO for DCI and ACI measurements.
Amps fuse holder Holds current fuse for front panel amps input.

1-14 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Rear panel summary

The rear panel of Model 2750 is shown in Figure 1-2. As shown, slot covers are installed
on unused slots.

WARNING Slot covers must be installed on unused slots to prevent personal con-

tact with high voltage circuits.

Figure 1-2

Model 2750 rear panel

4321

DIGITAL I/O TRIG. LINK

!

RS-232

IEEE-488

SLT

1

MADE IN

U.S.A.

SLT

2

CAT I

KEITHLEY

SLOT COVER

KEITHLEY

SLOT COVER

KEITHLEY

SLOT COVER

SLT

3

SLT

4

!

SLT

5

6

1 DIGITAL I/O

Male DB-9 connector for digital input (trigger link in) and digital outputs.

2 TRIG LINK

Eight-pin micro-DIN connector for sending and receiving trigger pulses among connected instruments.
Use a trigger link cable or adapter, such as Models 8501-1, 8501-2, 8502, and 8503.

3 RS-232

Female DB-9 connector for RS-232 operation. Use a straight-through (not null modem) DB-9 shielded
cable.

4 IEEE-488

Connector for IEEE-488 (GPIB) operation. Use a shielded cable, such as Models 7007-1 and 7007-2.

5 Power module

Contains the AC line receptacle, power line fuse, and line voltage setting. The instrument can be
configured for line voltages of 100V/120V/220V/240VAC at line frequencies of 50 or 60Hz.

5

WARNING Slot covers must be installed on unused slots to prevent personal

contact with high voltage circuits.

6 Slots 1 through 5

Five slots to accommodate Keithley Model 77XX series switching modules. The Model 2750 is shipped
from the factory with slot covers installed. Please note additional slot covers can be requested from
Keithley Instruments.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-15

Rack mounting

The Model 2750 can be mounted in a standard 19-inch rack. For a mainframe that has one
or no switching modules installed, the Model 2750 can be secured to the front rails of the
rack.

The hardware necessary to secure the mainframe to the front rails of the rack is supplied
with the Model 2750. The supplied hardware kit includes four dress screws and four
retaining clips. Each retaining clip has a captive nut.

Perform the following steps to mount the Model 2750 to front rails of the rack:

WARNING Make sure the Model 2750 is turned off, the line cord is disconnected,

and it is not connected to any external circuitry.

1. Select a location in the rack. The mainframe takes up 3½-inches of vertical space.

2. Using Figure 1-3 as a guide, install two retaining clips on the left front rail. Slide
each retaining clip over a mounting hole such that the captive nut is positioned on
the inside of the rack cabinet. In a similar manner, install two retaining clips on the
right front rail.

3. Remove the four foot assemblies from the bottom of the Model 2750. The retaining
screw for an assembly is located under the rubber foot. Simply pull off the rubber
feet to gain access to the screws. Retain these foot assemblies for future use.

4. Position the Model 2750 in the rack and loosely attach the front panel to the rack
rails using the four supplied dress screws.

5. Tighten the four dress screws.

CAUTION For a Model 2750 that has two or more installed switching modules,

rear brackets are required to support the additional weight. The
Model 4288-7 is a rack mount kit for the Model 2750 that uses rear
support brackets.

Figure 1-3

Rack preparation

Left Front
Rack Rail

1.75”

Retaining Clips
with Nuts

1-16 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Power-up

Line power connection

Follow the procedure below to connect the Model 2750 to line power and turn on the
instrument.

1. Check to see that the line voltage indicated in the window of the fuse holder
assembly (Figure 1-4) is correct for the operating voltage in your area. If not, refer
to the next procedure, “Setting line voltage and replacing fuse,” page 1-17.

CAUTION Operating the instrument on an incorrect line voltage may cause

damage to the instrument, possibly voiding the warranty.

2. Before plugging in the power cord, make sure that the front panel power switch is
in the off (O) position.

3. Connect the female end of the supplied power cord to the AC receptacle on the rear
panel. Connect the other end of the power cord to a grounded AC outlet.

WARNING The power cord supplied with the Model 2750 contains a separate

ground wire for use with grounded outlets. When proper connections
are made, instrument chassis is connected to power line ground
through the ground wire in the power cord. Failure to use a grounded
outlet may result in personal injury or death due to electric shock.

4. Turn on the instrument by pressing the front panel power switch to the on (I)
position.

Line frequency

The Model 2750 will operate at line frequencies from 45Hz to 66Hz, and 360Hz to 440Hz.
There are no user-settings for line frequency. It is automatically sensed at power-up. The
following command can be used to read the line frequency:

SYSTem:LFRequency? ' Query power line frequency.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-17

Figure 1-4

Power module

Model 2750

DIGITAL I/O TRIG. LINK

!

RS-232

IEEE-488

SLT

1

MADE IN
U.S.A.

SLT

2

CAT I

KEITHLEY

SLOT COVER

KEITHLEY

SLOT COVER

KEITHLEY

SLOT COVER

Fuse

Line Voltage

Selector

220

240

120

100

Spring

Window

Fuse Holder Assembly

SLT

3

SLT

4

!

SLT

5

Setting line voltage and replacing fuse

A rear panel fuse located next to the AC receptacle protects the power line input of the
instrument. If the line voltage setting needs to be changed or the line fuse needs to be
replaced, perform the following steps.

WARNING Make sure the instrument is disconnected from the AC line and other

equipment before changing the line voltage setting or replacing the line
fuse.

1. Place the tip of a flat-blade screwdriver into the power module by the fuse holder
assembly (Figure 1-4). Gently push in and up. Release pressure on the assembly
and its internal spring will push it out of the power module.

1-18 Getting Started Model 2750 Multimeter/Switch System User’s Manual

2. Remove the fuse and replace it with the type listed in Table 1-2.

CAUTION For continued protection against fire or instrument damage, only

replace fuse with the type and rating listed. If the instrument
repeatedly blows fuses, locate and correct the cause of the trouble
before replacing the fuse.

3. If configuring the instrument for a different line voltage, remove the line voltage
selector from the assembly and rotate it to the proper position. When the selector is
installed into the fuse holder assembly, the correct line voltage appears sideways in
the window.

4. Install the fuse holder assembly into the power module by pushing it in until it
locks in place.

Table 1-2

Fuse ratings

Line voltage Fuse rating Keithley P/N

100/120V
220/240V

Power-up sequence

On power-up, the Model 2750 performs self-tests on its EPROM and RAM and
momentarily lights all segments and annunciators. If a failure is detected, the instrument
momentarily displays an error message and the ERR annunciator turns on. (Error
messages are listed in Appendix C).

NOTE If a problem develops while the instrument is under warranty, return it to

Keithley Instruments, Inc., for repair.

If the instrument passes the self-tests, the firmware revision levels are displayed. An
example of this display is:

REV: A01 A01

where: First A01 is the main board ROM revision.

Second A01 is the display board ROM revision.

Installed switching modules are then displayed. For example, if there is a Model 7700
switching module installed in all five slots, the following messages will be displayed:

1: 7700 2: 7700
3: 7700 4: 7700

5: 7700

0.630A, 250V, slow-blow 5×20mm

0.315A, 250V, slow-blow 5×20mm

FU-106-.630
FU-106-.315

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-19

If a slot is empty, the message “NONE” will be displayed instead.

If the saved power-on setup is not the factory defaults setup (SYSTem:POSetup PRESet),
a message to identify the setup will be briefly displayed (“Defaults and user setups,”

page 1-21).

After the power-up sequence, the instrument begins its normal display of readings.

NOTE The serial number of the Model 2750 can be displayed by selecting the SNUM

item of the SETUP menu. Press SHIFT and then SETUP to access the menu. For
remote operation, the serial number can be read using the *IDN? command (see

Section 12 for details).

Keyclick

With keyclick enabled, an audible “click” will sound when a front panel key is pressed.
Perform the following steps to disable or enable keyclick:

1. Press SHIFT and then LOCAL to display the present state of KEYCLICK (ON or
OFF).

2. Press

 or  to display the desired keyclick state and press ENTER.

Display

Status and error messages

Remote programming

The following command controls keyclick:

SYSTem:KCLick <b> ' Enable or disable keyclick.

where: <b> = ON or OFF

NOTE Keyclick ON is the FACTORY, *RST, and SYSTem:PRESet default.

Readings are displayed in engineering units (i.e., 100.23mV), while annunciators indicate
various states of operation. See “Front panel summary,” page 1-10, for a complete listing
of display annunciators.

NOTE The display test allows you to test display digit segments, annunciators and the

red slot indicator LEDs. The key test checks the functionality of front panel keys.
These tests are accessed by pressing SHIFT and then TEST. Refer to the
Model 2750 Service Manual for details.

Status and error messages are displayed momentarily. During operation and programming,
you will encounter a number of front panel messages. Typical messages are either of status
or error variety, as listed in Appendix C.

1-20 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Remote programming — display

Using remote programming, the Model 2750 can display a custom ASCII message (up to
12 characters). Also, the front panel display and controls can be disabled.

Display commands

The commands are listed in Table 1-3. Details on these commands follow the table.

NOTE Optional command words and queries are not included in Table 1-3. Table 15-2

provides an unabridged list of all display commands.

Table 1-3

Display commands

Command Description Default*

DISPlay:TEXT:DATA <a> Define message (<a> = ASCII characters, up to 12). (none)
DISPlay:TEXT:STATe <b> Enable or disable message mode (<b> = ON or OFF). OFF
DISPlay:ENABle <b> Enable or disable the front panel display (<b> = ON or OFF). ON

*SYSTem:PRESet and *RST have no effect on DISPlay commands. The listed defaults are power-on defaults.

DISPlay:TEXT:DATA <a> Define text message

This command defines the text message for display. A message can be as long as 12
characters. A space counts as a character. Excess message characters results in an error.
The characters must be enclosed in either single quotes (‘ ’) or double quotes (“ ”).

DISPlay:TEXT:STATe ON | OFF Control (on/off) message for display

This command enables and disables the text message mode. When enabled, a defined
message is displayed. When disabled, the message is removed from the display.

A user defined text message remains displayed only as long as the instrument is in remote.
Taking the instrument out of remote (by pressing the LOCAL key or sending GTL)
cancels the message and disables the text message mode.

DISPlay:ENABle ON | OFF Control display circuitry

This command is used to enable and disable the front panel display circuitry. When
disabled, the instrument operates at a higher speed. While disabled, the display is blanked.

All front panel controls (except LOCAL) are disabled. Normal display operation can be
resumed by using the ENABle command to enable the display or by putting the
Model 2750 into local mode (press LOCAL).

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-21

Programming example

The following command sequence displays the text message “TESTING”:

DISP:TEXT:DATA 'TESTING' ' Define text message.
DISP:TEXT:STAT ON ' Enable text message mode.

Defaults and user setups

Model 2750 can be restored to one of two default setup configurations (FACTory or
*RST), or three user-saved (SAV0, SAV1, or SAV2). As shipped from the factory,
Model 2750 powers up to the factory (FACT) default settings.

NOTE Closed channels can be saved in a user setup (SAV0, SAV1, or SAV2). When the

setup is restored, those channels (and only those channels) will be closed. FACT
and *RST defaults opens all channels.

The factory default setup provides continuous triggering, while the *RST default setup
places the Model 2750 in the one-shot trigger mode. With one-shot triggering, a measure­ment is performed whenever the TRIG key is pressed or an initiate command is sent over
the remote interface.

The factory and *RST default settings are listed in Table 1-4. Setting differences (Set Diff)
between the two default setups are indicated by checkmarks (✓).

For remote programming, the SYSTem:PRESet and *RST commands are used to reset the
instrument. The *RST command returns the instrument to the *RST defaults and, for the
most part, the SYSTem:PRESet command returns the instrument to the factory default
conditions. The exceptions are explained as follows:

• Auto scan and auto channel configuration — FACTory defaults disable auto scan
and auto channel configuration, while SYSTem:PRESet has no effect. The *RST
defaults (front panel and remote operation) have no effect.

• Memory buffer auto clear — FACTory defaults enable buffer auto clear, while
SYSTem:PRESet has no effect. The *RST defaults (front panel and remote opera­tion) have no effect.

The instrument will power up to whichever default setup is saved as the power-on setup.

NOTE At the factory, the factory default setup is saved as the SAV0, SAV1, or SAV2

setups.

1-22 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Saving and restoring setups

Saving a user setup

1. Configure Model 2750 for the desired measurement application.

2. Press SHIFT and then SAVE to access the save setup menu.

3. Press

4. Use the

Saving a power-on setup

1. Configure Model 2750 for the desired measurement application.

2. Press SHIFT and then SAVE to access the save setup menu.

3. Press the

4. Press

5. Use the

 to place the cursor on the present setup (SAV0, SAV1, or SAV2).

 or  key to display the desired setup and press ENTER. The instrument

returns to the normal measurement state.

 key to display the present power-on (PWR-ON) setup: FACT, *RST,

SAV0, SAV1, or SAV2.

 to place the cursor on the present power-on setup.

 or  key to display the desired setup and press ENTER. The instrument

returns to the normal measurement state.

Restoring a setup

1. Press SHIFT and then SETUP to access the restore setup menu.

2. Press

3. Use the

NOTE If the settings for a user setup or power-on setup do not match the switching

 to place the cursor on the present RESTORE setup (FACT, *RST, SAV0,

SAV1, or SAV2).

 or  key to display the desired setup and press ENTER. The instrument

returns to the normal measurement state.

module types presently installed in the Model 2750, error +520 (Saved setup
scancard mismatch) occurs when the setup is recalled. The scan list will reset to
the factory defaults and all channels will open. However, the saved setup is still
retained in memory and can be restored when the matching switching module is
later installed.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-23

Table 1-4

Default settings

Setting Factory *RST Set Diff

Auto channel configuration No (off) No effect ✓
Autozero On On
Buffer No effect No effect

Auto clear Yes (on) No effect ✓
Channel Average Off Off
Closed channels None None
Closure count interval No effect No effect
Continuity

Beeper On On

Digits 4½ digits 4½ digits

Range 1kΩ 1kΩ

Rate Fast (0.01 PLC) Fast (0.01 PLC)

Threshold level 10Ω 10Ω
Current (AC and DC)

Bandwidth (AC) 30 30

Digits (AC) 5½ digits 5½ digits

Digits (DC) 6½ digits 6½ digits

Filter On Off ✓

Window 0.1% 0.1%
Count 10 10

Type Moving Repeat ✓
Range Auto Auto
Rate (DC) Slow (5 PLC) Slow (5 PLC)
Rel Off Off

Dry circuit ohms Off Off
Frequency and Period

Digits 6½ digits 6½ digits
Range 10V 10V
Rate (aperture) 1 second 1 second
Rel Off Off

Function DCV
GPIB No effect No effect

Address No effect (16 at factory) No effect (16 at factory)

Keyclick On On

1-24 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Table 1-4 (continued)

Default settings

Setting Factory *RST Set Diff

Limits Off Off

LO Limit 1 -1 -1
HI Limit 1 +1 +1
LO Limit 2 -2 -2

HI Limit 2 +2 +2
Line Synchronization Off Off
Math

mX+B Off Off

Scale Factor 1.0 1.0
Offset 0.0 0.0
Units “X” “X”

Percent Off Off

Reference 1.0 1.0

1/X (Reciprocal) Off Off
Monitor Off Off
Output

Beeper Never Never

Digital Output Off Off

Logic Sense High High

Pulse No (off) No (off)
Ratio Off Off
Resistance (Ω2 and Ω4)

Digits 6½ digits 6½ digits

Filter On Off ✓

Window 0.1% 0.1%
Count 10 10

Type Moving Repeat ✓
Offset compensation (OCOMP) Off Off
Dry circuit Off Off
Range Auto Auto
Rate Slow (5 PLC) Slow (5 PLC)
Rel Off Off

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-25

Table 1-4 (continued)

Default settings

Setting Factory *RST Set Diff

RS-232 Off Off

Baud rate No effect No effect
Flow control XonXoFF XonXoFF
Terminator No effect No effect

Scanning Disabled Disabled

Auto scan No (off) No effect ✓
Type (Simple or Advanced) No effect No effect
Simple scan

Minimum channel 101, 201, 301, 401, or 501 101, 201, 301, 401, or 501
Maximum channel No effect No effect
Timer Off Off
Reading count No effect No effect

Advanced scan

Setup No effect No effect
Immediate trigger On On

Limit triggers Off Off
Timer Off Off
Reading count No effect No effect

Temperature

Digits 5½ digits 5½ digits
Filter On Off ✓

Window 0.1% 0.1%
Count 10 10
Type Moving Repeat ✓

Rate Slow (5 PLC) Slow (5 PLC)
Rel Off Off
Sensor Thermocouple Thermocouple

Junction See Note See Note
Open detector No (off) No (off)
Type K K
Units °C °C

Timestamp No effect No effect
Triggering Continuous One-shot ✓

Delay Auto Auto
Source Immediate Immediate

1-26 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Table 1-4 (continued)

Default settings

Setting Factory *RST Set Diff

Voltage (AC and DC)

dB Off Off

Reference 1.0 1.0
Digits (AC) 5½ digits 5½ digits
Digits (DC) 6½ digits 6½ digits
Filter On Off ✓

Window 0.1% 0.1%

Count 10 10

Type Moving Repeat ✓
Range Auto Auto
Rate (DC) Slow (5 PLC) Slow (5 PLC)
Rel Off Off

Note: With a Model 7700, 7706, or 7708 installed, the default sensor junction is Internal. Otherwise, the Simulated (23ºC) junction is

selected.

Remote programming — default and user setups

Default and user setup commands are listed in Table 1-5.

NOTE The SYSTem:PRESet and *RST defaults are listed in the SCPI tables in

Section 15.

Table 1-5

Default setup commands

Commands Description

SYSTem:PRESet Restore SYSTem:PRESet defaults.
*RST Restore *RST defaults.

*SAV <NRf> Save settings as user-setup; <NRf> = 0, 1 or 2.
*RCL <NRf> Restore user-saved setup; <NRf> = 0, 1 or 2.

SYSTem:POSetup <name> Specify power-on setup; <name> = RST, PRESet, SAV0,

SAV1, or SAV2.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-27

Programming example

*SAV 2 ' Save present setup in memory location 2.
SYST:POS SAV2 ' Specify SAV2 setup as the power-on setup.
*RST ' Return 2750 to RST defaults.
*RCL 2 ' Return 2750 to setup stored in memory location 2.

Remote programming information

Remote programming information is integrated with front panel operation throughout this
manual. Programming commands are listed in tables, and additional information that
pertains exclusively to remote operation is provided after each table. The tables may
reference you to other sections of this manual.

NOTE Except for Section 11 through Section 15, most programming tables in this

manual are abridged. That is, they exclude most optional command words and
query commands. Optional command words and query commands are
summarized as
follows.

Optional command words — In order to be in conformance with the IEEE-488.2
standard, Model 2750 accepts optional command words. Any command word that is
enclosed in brackets ([]) is optional and does not have to be included in the program
message.

Query commands — Most command words have a query form. A query command is
identified by the question mark (?) that follows the command word. A query command
requests (queries) the programmed status of that command. When a query command is
sent and Model 2750 is addressed to talk, the response message is sent to the computer.

NOTE For complete details, see “Programming syntax,” page 10-10.

1-28 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Quick start exercises

This section topic summarizes the following basic instrument operations and provides
simple exercises to perform them:

• Basic DMM measurements — front panel inputs

• Closing and opening channels — system channel operation

• Simple scanning

• Trigger and return readings — remote programming

WARNING For the exercises, it is not necessary to connect an input signal or DUT

to the instrument (front panel inputs or switching module inputs).
However, if you decide to use an input signal, it is recommended that
you keep it at a nonhazardous level (<42V) while learning to use the
instrument.

NOTE When using the front panel input terminals, the INPUT switch must be in the

“F” (out) position. The INPUT switch is located on the right side of the front
panel near the input terminals. When using a switching module, the switch must
be in the “R” (in) position.

Basic DMM measurements — front panel inputs

NOTE See Section 3 for details on basic DMM operation.

The Model 2750 is shipped from the factory to power-up to factory defaults. The
instrument powers up to a setup that continuously measures DC volts. Some of the default
settings for the DCV function include auto range enabled, 6∫-digit resolution, filter
enabled, and slow reading rate. These settings provide a good starting point and in many
cases, do not need to be changed.

“Starting-point” default settings are also provided for the other measurement functions.
Therefore, to perform basic measurements, simply select the desired function, and
“tweak” the setup (range, rate, filter, digits, etc.) as required.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-29

For remote programming, the instrument is typically used in a non-continuous
measurement mode. In this mode, the user (via remote command programming) specifies
the number of measurements to perform. *RST defaults place the instrument in a non­continuous measurement mode. Most of the other settings for factory and *RST defaults
are the same.

For remote programming, the following command is used to select function.

NOTE Items in brackets ([]) are optional and do not need to be included. Upper case

characters are required. Lower case characters are optional and need not be
included.

[SENSe[1]]:FUNCtion <func> ' Select measurement function.

<func> = 'VOLTage[:DC]'

'VOLTage:AC' ACV
'CURRent[:DC]' DCI
'CURRent:AC' ACI
'RESistance' Ω2
'FRESistance' Ω4
'FREQuency' FREQ
'PERiod' PERIOD
'TEMPerature' TEMP

DCV

Each function can have its own unique setup configuration (i.e., range, digits, speed, etc.).
For example, the following command words select range and digits:

RANGe[:UPPer] <n> ' Specify expected reading.
RANGe:AUTO <b> ' Enable (ON) or disable (OFF) auto range.
DIGits ' Set display resolution; 3.5, 4.5, 5.5 or 6.5 (digits).

The following examples demonstrate how to include the function name in the command
string for configuration commands.

VOLT:RANG 10 ' Select 10V range for DCV.
RES:RANG:AUTO ON ' Enable auto range for W2.
CURR:DIG 4.5 ' Set DCI for 4½- digit resolution.

NOTE See Section 4 for details on setting range, digits, rate, bandwidth, and filter.

1-30 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Exercise 1 — Basic DMM measurements

The exercise in Table 1-6 measures ACV on the 10V range and stores 15 readings in the
buffer.

Table 1-6

Exercise 1 — Measure AC volts - store readings in buffer

Front panel operation Command sequence

1 For front panel operation, proceed to step 2.

For remote programming, clear the buffer

1

:

TRAC:CLE

2 Restore defaults2:

Press SHIFT > press SETUP > select RESTORE: FACT.

*RST

3 Select ACV function:

Press ACV.

FUNC 'VOLT:AC'

4 Select 10V range:

Press RANGE  to display “RANGE: 10V”.

VOLT:AC:RANG 10

6 Store 15 readings in buffer3:

Press STORE > set for 000015 RDGS > press ENTER.

SAMP:COUN 15

READ?

7 Recall buffer readings4:

Press RECALL > use edit keys to display readings. Press EXIT to exit

CALC1:DATA?

recall mode.

1. To avoid problems with remote programming, it is good practice to routinely clear the buffer (TRAC:CLE) at the beginning
of a program that performs multiple measurements (
the buffer.

2. FACTory defaults place the instrument in a continuous measurement mode. *RST places the instrument in a non­continuous measurement mode.

3. READ? triggers and returns 15 readings. These 15 readings are automatically stored in the buffer. See Exercise 4 and 5 for
more information on the READ? command.

4. Statistics for buffer readings are also stored in the buffer. For remote programming,
ings that were stored. It does not return buffer statistics.
(see Section 6 for details).

SAMP:COUN >1). Restoring *RST or FACTory defaults does not clear

CALC1:DATA? only returns the read-

CALC2 commands are used to calculate and return buffer statistics

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-31

Closing and opening channels — system channel operation

NOTE See Section 2 for details on closing and opening switching module channels.

NOTE The following discussion assumes a multiplexing switching module

(i.e., Model 7700) installed in slot 1 of the mainframe. Switching module
installation is covered in “Switching module installation and connections,”

page 2-3.

An alternative to installing a switching module is to assign slot 1 as a
pseudocard using remote programming. The instrument will operate as if a
switching module is installed in slot 1. To “install” a 7700 pseudocard in slot 1,
send the following command:

SYST:PCAR1 C7700

System channel operation is used to connect input channels to the DMM of the
Model 2750:

• For a 2-wire function (i.e., DCV), closing a system channel connects the input to
DMM Input of the Model 2750.

Figure 1-5 shows system channel 1 closed. For the Ω2 function, the resistance

(DUT) would be connected to DMM Input as shown Figure 1-5.

• For a 4-wire function (i.e., Ω4), a channel pair is connected to the DMM when a
system channel is closed. The system channel is connected to DMM Input and the
paired channel is connected to DMM Sense.

Figure 1-6 shows system channel 6 closed. For a 4-wire function, the paired

channel also closes. For the Model 7700, channels 1 through 10 are paired to
channels 11 through 20. When channel 6 is closed, channel 16 also closes.

Figure 1-6 shows how the DUT is connected to the DMM for the 4-wire function.

NOTE Figure 1-5 and Figure 1-6 show simplified schematics of the switching module.

They show a single switch closed to connect an input channel to the DMM. In
reality, multiple switching to is used to make proper connections to the DMM.
However, for system channel operation, the user need not be concerned about
which switches in the module close.

Figure 1-5

Connection to DMM for 2-wire function (system channel 101 closed)

Switching Module Switching Module

HI

Ch 1

LO

DMM

HI

Input

LO

DUT

HI

Ch 1

LO

DMM

HI

Input

LO

1-32 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Figure 1-6

Connection to DMM for 4-wire function (system channel 106 closed)

Switching Module

HI

Ch 6

LO

HI

Ch 16

LO

7700

HI

Input

LO

HI

Sense

LO

HI

Ch 6

LO

DUT

HI

Ch 16

LO

7700

Switching Module

HI

Input

LO

DMM DMM

HI

Sense

LO

NOTE Switching module channels can also be controlled using multiple channel

operation. This allows individual control of all module channels (switches).
Multiple channel operation should only be used by experienced service
personnel who recognize the dangers associated with multiple channel closures.
See Section 2 for details.

Close/open operation

The following points on operation pertain to system channel operation only:

• Only one input channel (or channel pair) is closed at one time. When you close an
input channel, the previously closed input channel(s) will open.

• When a system channel is closed, the channel number will be displayed on the
Model 2750. The slot number for the module is also displayed. For example, “103”
indicates that system input channel 3 for a module in slot 1 is closed.

• The paired channel for a 4-wire function is not displayed. Only the system channel
number is displayed. For example, in Figure 1-6, channel number 106 will be
displayed with the Model 7707 installed in slot 1 of the mainframe.

• Switching modules that have current measurement capability have separate
channels reserved exclusively for the DCI and ACI functions. For example, the
Model 7700 has channels 21 and 22 reserved for amps measurements. With the
DCI or ACI function selected, only channels 21 and 22 can be closed. These
channels cannot be accessed on any other function.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-33

Figure 1-7 shows the front panel keys used to close and open system channels.

Figure 1-7

Front panel keys to close and open system channels

Close next

measurement

channel

CLOSEOPEN

Press CLOSE key

CLOSEOPEN

Press OPEN key

CLOSE:SINGLE

Close previous

measurement

channel

A. Sequencing through channnels B. Specifiying channel to close C. Opening all channels

CLOSE CH: XXX

Display SINGLE option
and press ENTER

Specify channel
number (XXX) and
press ENTER

OPEN: ALL

Display ALL
option and press
OPEN again

For remote programming, the following three commands are used for basic system
operation to open and close input channels:

ROUTe:CLOSe <clist> ' Close specified system channel1.
ROUTe:CLOSe? ' Query closed system channel2.
ROUT:OPEN ALL ' Open all channels.

1. Only one channel can be specified in the <clist>. For example, to close input
channel 3 for a module in slot 1, the following command would be sent:

ROUTe:CLOSe (@103)

2. Only the closed system channel is returned by ROUTe:CLOSe?. The paired channel
for a 4-wire function is not returned. For example, assume channel 2 in slot 1 is
closed. The following response message will be returned:

(@102)

1-34 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Exercise 2 — Closing and opening channels (system channel operation)

The exercise in Table 1-7 demonstrates a sequence to close and open channels of a
Model 7700 installed in slot 1 of the mainframe.

Table 1-7

Exercise 2 — Close and open channels (system channel operation)

Front panel operation Command sequence

1 Open all channels*:

Press OPEN > display OPEN:ALL > Press OPEN.

ROUT:OPEN ALL

2 Select Ω2 function:

Press Ω2.

FUNC 'RES'

3 Close system channel 101:

Press the

 key. Channel 1 connects to DMM Input (see Figure 1-5).

ROUT:CLOS (@101)

4 Close system channel 102:

Press the

 key. Channel 2 connects to DMM Input.

ROUT:CLOS (@102)

5 Close system channel 106:

Press CLOSE > select CLOSE:SINGLE > key in channel 106 > press

ROUT:CLOS (@106)

ENTER. Channel 6 connects to DMM Input.

6 Select Ω4 function:

Press Ω4. 4W annunciator turns on, and channels 6 and 16 connects to

FUNC 'FRES'

DMM Input and Sense (see Figure 1-6).

7 Open all channels*:

Press OPEN > display OPEN:ALL > Press OPEN ROUT:OPEN ALL

*It is a good, safe practice to start and end a switching sequence by opening all channels.

Simple scanning

NOTE See Section 7 for details on scanning.

With at least one multiplexer switching module (i.e., Model 7700) installed in the
mainframe, the instrument can scan channels that are valid for the selected function.

For front panel operation, Figure 1-8 shows the three basic steps to configure and run a
simple scan. The differences between the STEP function and the SCAN function involve
the reading count and the timer.

Reading count (RDG CT) — For both STEP and SCAN, the reading count specifies the
number of readings to store in the buffer. For STEP, the reading count determines the
number of channels to scan.

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-35

For SCAN, the reading count also determines the number of scans to perform and is best
explained by an example. Assume there are 10 channels in the scan list (i.e., 101 through

110). If you set the reading count to 10 or less, one scan of the 10 channels will be
performed. If you set the reading count to any value from 11 to 20, two scans will be
performed. A reading count from 21 to 30 gives you three scans, and so on.

Timer interval (TIMER) — For the STEP function, the timer specifies the time delay
between scanned channels. For the SCAN function, the interval specifies the time delay
between scans. The timer starts when the scan is started. For SCAN, the next scan will not
start until the timer interval expires.

NOTE The Model 2750 can also be configured to run an advanced scan. For an

advanced scan, each channel can have its own unique setup (i.e., function,
range, etc.). Advanced scanning is covered in Section 7.

Figure 1-8

Simple scan operation

Step 1. Configure simple scan: Step 2. Run simple scan:

Press SHIFT

SHIFT

Step 3. Disable scan mode:

Press SHIFT

SHIFT

CONFIG

SCANSTEP

INT: SIMPLE

MIN CHAN: XXX

MAX CHAN: YYY

TIMER? NO/YES

YESNO

xxH:xxM:xx.xxxS

RDG CT:xxxxxx

HALT

SCANSTEP

Press CONFIG (STEP)

Display SIMPLE option
and press ENTER

Specify minimum channel
(XXX) and press ENTER

Specify maximum channel
(YYY) and press ENTER

Display NO or YES and
press ENTER

Set timer interval in
hr:min:sec format and
press ENTER

Specify reading count and press
ENTER

Press HALT (SCAN)

SCANSTEP

Press STEP or SCAN to start
scan

Timer interval specifies time
between scans.

Reading count:
Specifies number of scans
to be performed.
Specifies number of readings
to store in buffer.

Timer interval specifies time between
scanned channels.

Reading count:
Specifies number of channels to be
scanned.
Specifies number of readings to store
in buffer.

1-36 Getting Started Model 2750 Multimeter/Switch System User’s Manual

For remote programming, the following commands are used for simple scanning:

ROUTe:SCAN <clist> ' Define scan list*.
TRIGger:COUNt <NRf> ' Specify number of scans (1 to 11000 or

' INFinity).
SAMPle:COUNt <NRf> ' Specify number of channels to scan (1 to 11000).
ROUTe:SCAN:LSELect <name> ' Enable (INT) or disable (NONE) scan.

*Any valid switching module channel can be included in the scan list. Make sure to list

them from the lowest numbered channel to the highest. For example, to scan channels 1
through 8 of a Model 7700 installed in slot 1, send the following command to define the
scan list:

ROUTe:SCAN (@101:108)

Exercise 3 — Simple scanning

The scanning example in Table 1-8 assumes a Model 7700 installed in slot 1 of the
mainframe. The scan will use default settings (DCV) to scan eight channels and store the
readings in the buffer.

Table 1-8

Exercise 3 — Simple scanning

Front panel operation Command sequence

1 For front panel operation, proceed to step 2.

For remote programming, clear the buffer:

TRAC:CLE

2 Restore defaults1:

Press SHIFT > press SETUP > select RESTORE: FACT.

*RST

3 Configure scan:

Press SHIFT > press CONFIG > select INT: SIMPLE > set MIN
CHAN101 > set MAX CHAN: 108 > select TIMER? NO > set RDG

ROUT:SCAN (@101:108)
SAMP:COUN 8

CT:000008.

4 Enable and start scan2:

Press STEP.

ROUT:SCAN:LSEL INT
INIT

5 Halt (disable) scanner:

Press SHIFT > press HALT.

ROUT:SCAN:LSEL NONE

6 Recall the eight stored readings:

Press RECALL > use edit keys to display readings. Press EXIT to

CALC1:DATA?

exit recall mode.

7 Open all channels:

Press OPEN > display OPEN:ALL > Press OPEN

1. Factory and *RST defaults opens all channels, select the DCV function and sets TRIG:COUN to 1. The trigger count speci­fies the number of scans to be performed.

2. ROUT:SCAN:LSEL INT enables the scan, and INIT triggers the start of the scan.

ROUT:OPEN ALL

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-37

Trigger and return readings — remote programming

There are several commands used to trigger and return readings. The proper commands
and sequence to use depend on trigger state (continuous or non-continuous) and what you
are trying to accomplish.

Presented here are three fundamental command sequences that can be used to “trigger and
return readings.” These three command sequences (exercises) will accommodate most
basic measurement scenarios. Simply use the command sequence (exercise) that satisfies
your needs:

• Exercise 4 — Trigger and return a single reading

• Exercise 5 — Trigger and return multiple readings

• Exercise 6 — Return a single reading (continuous triggering)

Details on the commands to trigger and return readings are provided in other sections of
this manual. For details, refer to the following sections:

Section 3 — See “Trigger and retrieve readings” in Table 3-7.
Section 7 — For scanning, see “Trigger commands” in Table 7-1.
Section 8 — Explains the triggering process.
Section 13 — Covers Signal Oriented Measurement Commands (i.e., FETCh?, READ?).
Section 15 — See Table 15-9 (Trigger command summary).
Appendix D — Shows how trigger and read commands control data flow within the

instrument.

NOTE Each exercise indicates the commands used to configure triggering. Once

triggering is configured, the commands to trigger and/or return readings can be
repeated as often as desired (unless noted otherwise).

Exercise 4 — Trigger and return a single reading
Exercise 5 — Trigger and return multiple readings

Trigger controlled measurements — The instrument is typically used in a non­continuous trigger mode. In this mode, commands are used to trigger one or more
readings. After the specified number of readings are completed, the measurement process
stops.

Exercise 4 in Figure 1-9 provides a command sequence to trigger and return one reading.
Exercise 5 in Figure 1-10 provides a command sequence to trigger and return multiple
readings.

1-38 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Exercise 6 — Return a single reading (continuous triggering)

Readings can be returned while the instrument is in the continuous measurement (trigger)
mode. Each time a read command is sent, the latest reading is returned. Exercise 6 in

Figure 1-11 provides a command sequence to return a single reading while in the

continuous trigger state.

Figure 1-9

Exercise 4 — Trigger and return a single reading

INIT:CONT OFF

TRIG:COUN 1

Trigger Configuration

SAMP:COUN 1

INITTrigger Reading

Trigger and Return
Reading

FETCh?

OR

CALC:DATA?

Return Result of MATH
Calculation

1. If a MATH function (mX+B, percent or 1/X) is enabled, the result of the calculation will
be returned (MATH functions are covered in Section 5).

2. If there is no MATH function enabled, FETCh?and CALC:DATA? will return the basic
reading.

3. FETCh?, CALC:DATA?, and DATA? do not trigger readings. They simply return the last
reading. If you again send one of these commands before triggering a new reading, the
old reading will be returned.

4. DATA:FRESh? can only be used once to return the same reading. Sending it again

1, 2, 3

without first triggering a new reading will cause error -230 (data corrupt or stale).

DATA ?

OR

DATA:FRESh?

Return Basic Reading

3,4

Place 2750 in
non-continuous
trigger state

Set 2750 to perform
one measurement

READ?

1

Trigger and Return

Reading

Model 2750 Multimeter/Switch System User’s Manual Getting Started 1-39

Figure 1-10

Exercise 5 — Trigger and return multiple readings

1

Trigger Configuration

TRAC:CLE

INIT:CONT OFF
TRIG:COUN 1

SAMP:COUN x

Clear Buffer

Place 2750 in non-continuous
trigger state

Set 2750 to perform “x”
number of measurements
(x = 2 to 110000)

INIT
FETCh?

OR

READ?

Trigger and Return
Readings

2, 3

Trigger and Return

Readings

TRAC:DATA?

Return Stored Readings

4

1. In order to trigger and return multiple readings, the buffer must first be cleared of
readings that were stored by the TRACe command or front panel operation (see
Section 6 for details on buffer operation).

2. INIT triggers the measurements, and FETCh? returns the readings. Again sending
FETCh? without first sending INIT will return old readings.

3. READ? performs an INIT to trigger the measurements, and then FETCh? to return
the reading(s).

4. Triggered readings are automatically stored in the buffer. Statistics for buffer readings
are also stored in the buffer. CALC2 commands are used to calculate and return
buffer statistics (see Section 6 for details).

1-40 Getting Started Model 2750 Multimeter/Switch System User’s Manual

Figure 1-11

Exercise 6 — Return a single reading (continuous triggering)

Place 2750 in
continuous
trigger state.

DATA ?

OR

DATA:FRESh?

2, 3

Trigger Configuration

Return Readings

SAMP:COUN 1
INIT:CONT ON

FETCh?

OR

CALC:DATA?

Return result of MATH
Calculation

1, 2

Return Basic Reading

1. If a MATH function (mX+B, percent or 1/X) is enabled, the result of the calculation will
be returned. If there is no MATH function enabled, FETCh? and CALC:DATA? will return
the basic reading.

MATH functions are covered in Section 5.

2. None of these read commands trigger measurements. They simply return the lastest
reading. If FETCH?, CALC:DATA?, or DATA? is again sent before a new reading is
triggered, the ld reading will be returned.

3. DATA:FRESh? can only be used once to return the same reading. Sending it again before

a new reading is triggered will cause error -230 (data corrupt or stale).

2

Closing and Opening

Switching Module Channels

• Close/open overview — Summarizes the two operating modes to control switch­ing modules: system channel operation and multiple channel operation.

• Switching module installation and connections — Explains how to install a
switching module (or pseudocard) into the Model 2750 mainframe. Also explains
where to find connection information which should only be performed by qualified
service personnel.

• Channel assignments — Explains the format for specifying the mainframe
channel assignment which is made up of the slot number and switching module
channel number.

• System channel operation — Provides detailed information for using system
channel operation.

• Multiple channel operation — Provides detailed information for using multiple
channel operation. Due to safety considerations, this operating mode should only
be used by experienced test engineers.

• Identifying installed modules and viewing closed channels — Explains how to
use the CARD menu to identify installed switching modules and view closed
channels. Explains how to remotely identify installed modules (*OPT?) and
summarizes other query commands that can be used to acquire information about
the installed modules.

• Relay closure count — Explains how to determine the number of times switching
module relays have been closed.

• Model 7700 switching module — Covers operating characteristics that are unique
to the Model 7700. Also includes a simplified schematic diagram of the switching
module.

2-2 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Close/open overview

NOTE This section covers basic close/open operations for switching module channels.

It also covers the operating characteristics that are unique to the Model 7700
switching module. Unique operating characteristics for all switching modules
are provided in the Model 77XX Series Switching Modules Instruction Manual.

There are two modes of close/open operation:

• System channel operation — This is the mode of operation that should be used
exclusively by most (if not all) users. When you close an input channel (or channel­pair), other channels on the switching module close automatically to internally
connect it the DMM of the Model 2750.

• Multiple channel operation — This mode of operation provides additional
flexibility by providing individual control of each switching module channel.
However, careless operation could create a safety hazard and/or damage the
switching module and other equipment. Multiple channel operation should only be
used by experienced test engineers.

CAUTION To prevent damage to a switching module, do not exceed the maximum

signal level input for that module. Most switching modules are rated
for 303V. The following command queries maximum module voltage:

SYSTem:CARDx:VMAX? ‘ Request maximum allowable voltage for

‘ CARDx (where x is the slot number for
‘ the module).

For system channel operation, the instrument will display the
“OVERFLOW” message when the maximum allowable voltage for
the module is being exceeded.

However, for multiple channel operation, the “OVERFLOW” message
will not occur until the maximum voltage of the mainframe (not
module) is exceeded. Therefore, the “OVERFLOW” message would
occur only if 1010V is exceeded.

WARNING Careless multiple channel operation could create an electric shock

hazard that could result in severe injury or death. Improper operation
can also cause damage to the switching modules and external circuitry.
Multiple channel operation should be restricted to experienced test
engineers who recognize the dangers associated with multiple channel
closures.

NOTE The Model 2750 can scan switching module channels. Each channel in the scan

can have its own unique setup configuration. Scanning is covered in Section 7.

NOTE When a setup is saved as a user setup (SAV0, SAV1, or SAV2), closed channels

are also saved. When the setup is restored, those channels (and only those
channels) will be closed (see “Defaults and user setups,” page 1-21).

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-3

Switching module installation and connections

In order to exercise close/open operations explained in this section, a switching module
(or pseudocard) must be installed in the mainframe. A switching module can be installed
by the user, however external connections to the switching module are only to be
performed by qualified service personnel.

NOTE For inexperienced users, it is recommended that DUT and external circuitry not

be connected to switching modules. This will allow you to exercise close/open
operations without the dangers associated with live test circuits.

WARNING To prevent electric shock that could result in injury or death, NEVER

handle a switching module that has power applied to it:

• Before installing (or removing) a switching module, make sure the
Model 2750 is turned off and disconnected from line power.

• If the switching module is already connected to DUT, make sure
power is removed from all external circuitry.

Module installation

WARNING Slot covers must be installed on unused slots to prevent personal

contact with high voltage circuits.

Perform the following steps to install a switching module into the Model 2750 mainframe:

1. Turn the Model 2750 off and disconnect the power line cord and any other cable
connected to the rear panel.

2. Position the Model 2750 so you are facing the rear panel.

3. Remove the slot cover plate from the desired mainframe slot. Retain the plate and
screws for future use.

4. With the top cover of the switching module facing up, slide the module into an
empty slot. For the last ¼ inch or so, press in firmly to mate the module connector
to the mainframe connector.

5. On each side of the module, there is a mounting screw. Tighten these two screws to
secure the module to the mainframe. Do not overtighten.

6. Reconnect the power line cable and any other cables to the rear panel.

7. When you turn on the Model 2750, the model number of the switching module will
be briefly displayed.

2-4 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Connections

WARNING Connection information for switching modules is intended for qualified

service personnel. Do not attempt to connect DUT or external circuitry
to a switching module unless qualified to do so.

To prevent electric shock that could result in serious injury or death,
adhere to following safety precautions:

• Before making or breaking connections to the switching module,
make sure the Model 2750 is turned off and power is removed
from all external circuitry.

• Do not connect signals that will exceed the maximum
specifications of switching module. Specifications for the Model
7700 are provided in Appendix A.

If both the front panel terminals and the switching module terminals
are connected at the same time, the test lead insulation must be rated
to the highest voltage that is connected. For example, if 1000V is
connected to the front panel input, the test lead insulation for the
switching module must also be rated for 1000V.

Dangerous arcs of an explosive nature in a high energy circuit can
cause severe personal injury or death. If the multimeter is connected to
a high energy circuit when set to a current range, low resistance range,
or any other low impedance range, the circuit is virtually shorted.
Dangerous arcing can result even when the multimeter is set to a
voltage range if the minimum voltage spacing is reduced in the
external connections. For details to safely make high energy
measurements, see “High energy circuit safety precautions,” page 3-3.

As described in the International Electrotechnical Commission (IEC)
Standard IEC 664, the Model 2750 is Installation Category I and must
not be connected to mains.

For the Model 7700, detailed connection and wiring information is provided in

Appendix B of this manual (Model 7700 Connection Guide).

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-5

Pseudocards

Using remote programming, you can assign a pseudocard to an empty switching module
slot. With a pseudocard installed, the Model 2750 will operate as if the switching module
is installed in the Model 2750. This feature allows you exercise open/close/scan
operations, or configure your system without having the actual switching module installed
in the unit. There is a pseudocard for every Keithley Model 77XX series switching
module.

A pseudocard cannot be installed from the front panel. However, once it is installed, you
can take the Model 2750 out of remote and use the front panel. Pressing the LOCAL key
takes the Model 2750 out of remote.

When a pseudocard is installed, the appropriate front panel slot indicator lamp turns on.
When the instrument is turned off, the pseudocard will be lost (uninstalled). Use the
following commands to install pseudocards:

SYSTem:PCARd1 <name> ' Install pseudocard in slot 1.
SYSTem:PCARd2 <name> ' Install pseudocard in slot 2.
SYSTem:PCARd3 <name> ' Install pseudocard in slot 3.
SYSTem:PCARd4 <name> ' Install pseudocard in slot 4.
SYSTem:PCARd5 <name> ' Install pseudocard in slot 5.
<name> = C7700, C7701, C7702, C7703, C7705, C7706, C7707, C7708, C7709,

C7710, C7711, or C7712

Programming example — The following command sets up the Model 2750 to operate as
if a Model 7700 switching module is installed in slot 2, which must be empty. You cannot
assign a pseudocard to a slot that already has a switching module installed in it.

SYSTem:PCAR2 C7700 ' "Install" pseudocard 7700 for slot 2.

Channel assignments

The Model 2750 has five slots for switching modules. To control the appropriate switching
module, the slot number must be included with the switching module channel number
when you specify a channel. The channel assignment is formatted as follows:

SCH where: S is the slot number

CH is the channel number

Examples:

101 = Slot 1, Channel 1
210 = Slot 2, Channel 10
506 = Slot 5, Channel 6

NOTE For remote operation, the 3-digit channel assignment is included in the channel

list parameter for the commands. Format examples for the channel list
parameter are provided in Table 2-1 and Table 2-2.

2-6 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

System channel operation

The system channel is a closed measurement channel that is internally connected to the
internal DMM Input of the Model 2750. The system channel number is displayed on the
Model 2750. For a 4-wire function (i.e., Ω4), the paired channel for the system channel is
internally connected to DMM Sense. The paired channel is not displayed on the
Model 2750. When triggered, the DMM performs a measurement and displays it on the
Model 2750.

The system channel is selected by closing a measurement channel using the system
channel close keys. These include the
option). See “Controlling the system channel,” page 2-9, for details.

Other important points about system channel operation include the following:

• There can only be one system channel. This is the channel that is presently
displayed (and closed) on the Model 2750. When a channel is not displayed, there
is no system channel.

• When a measurement channel is closed, the input backplane isolation channel also
closes to connect the system channel to DMM input. For a 4-wire function, the
paired channel and the sense backplane isolation channel also close to make the
sense connections to the DMM.

• When a different measurement channel is closed, the previous system channel
opens. The newly closed (and displayed) measurement channel becomes the
system channel.

• The system channel close keys can only close measurement channels that will
automatically connect to the DMM. Non-measurement channels cannot be closed
by the system channel close keys.

 and  keys, or the CLOSE key (SINGLE menu

NOTE Use the VIEW option of the CARD menu to display all closed channels in the

mainframe (see “CARD menu,” page 2-29).

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-7

2-wire functions

Figure 2-1 shows an example of how the system channel is connected to the DMM Input

of the Model 2750. Assume a Model 7700 switching module is installed in slot 1 of the
mainframe. When channel 101 is closed using the system channel close keys, both the
Channel 1 relay and the backplane isolation relay (Channel 25) closes to connect the
channel to the DMM. The complete simplified schematic of the Model 7700 is provided in

Figure 2-12.

Figure 2-1

2-wire system channel connections to Model 2750 DMM

Model 2750

Model 7700 Switching Module

Channel 1

Relay

HI

Channel 1

LO

System Channel Operation:
Close Channel 101

Slot 1

DMM

Channel 25

HI

Input

LO

Backplane

Isolation

Relay

2-8 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

4-wire functions (paired channels)

A 4-wire function, such as Ω4, requires that another measurement channel be paired to the
system channel. For example, if the switching module has 20 measurement channels,
channels 1 through 10 can be used as the system channel, while channels 11 through 20
are used as the paired channel. For a switching module that has 20 measurement channels,
channel 1 is paired to channel 11, channel 2 is paired to channel 12, channel 3 is paired to
channel 13, and so on.

Figure 2-2 shows an example of system channel connections for a 4-wire function.

Assume a Model 7700 switching module is installed in slot 1 of the mainframe, and a
4-wire function, such as Ω4, is selected. When channel 101 is closed using the system
channel close keys, the Channel 1 relay and the input backplane isolation relay
(Channel 25) closes to connect the channel to DMM Input. Also, the Channel 11 relay and
the sense backplane isolation relay (Channel 24) closes to connect the paired channel to
DMM Sense. Also note in Figure 2-2 that the Channel 23 relay closes to isolate channel 1
from channel 11.

The complete simplified schematic of Model 7700 is provided in Figure 2-12.

Figure 2-2

4-wire system channel connections to Model 2750 DMM

Model 7700 Switching Module

Channel 1

Relay

Channel 1

System Channel Operation:
Close Channel 101

Channel 11

HI

LO

Channel

(Closed Position

Shown

Channel 11

Relay

HI

LO

Model 2750

23

)

Channel 25

Backplane

Isolation

Relay

2-Pole/4-Pole

Relay

Channel 24

Backplane

Isolation

Relay

Slot 1

DMM

HI

Input

LO

HI

Sense

LO

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-9

Controlling the system channel

When a measurement channel is closed, a previous system channel (and, for a 4-wire
function, its paired channel) is first opened. The closed measurement channel becomes the
system channel. When a 4-wire function is selected, the paired channel for the system
channel also closes.

 and  keys

These front panel keys (Figure 2-3) can be used to select the next or previous
measurement channel as the system channel. If there are no measurement channels
available, one of the following messages will be briefly displayed when one of these keys
is pressed:

NO SCAN CARD — This message indicates that there are no switching modules (or
pseudocards) installed. All five slots are empty.

NO MEAS CARD — This message indicates that none of the installed switching
modules (or pseudocards) have measurement channels. For example, the Model 7705
switching module does not have any measurement channels. Those channels cannot be
internally connected to the DMM.

NOTE The

 and  keys can also be used to open all channels in the mainframe.

Simply increment or decrement the channel number until there is no channel
displayed.

Figure 2-3

System channel operation — closing next or previous measurement channel

Close previous

measurement

channel

Close next

measurement

channel

2-10 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

CLOSE key (SINGLE menu option)

The SINGLE menu option for the CLOSE key can be used to select a measurement
channel as the system channel (Figure 2-4). Perform the following steps to select the
system channel:

1. Press the CLOSE key. The message “CLOSE:SINGLE” message will be
displayed.

NOTE If the “CLOSE:MULTI” message is instead displayed when CLOSE is pressed,

it indicates that there are no measurement modules installed in the mainframe.
See “Multiple channel operation,” page 2-16, to close the channels of a non-
measurement module (i.e., Model 7705).

2. Press ENTER to display the prompt to close a channel (CLOSE CH: XXX).

3. Using

4. Press ENTER. The channel closes and the CHAN annunciator turns on.

An invalid channel cannot be closed and will cause one of the following error messages to
be briefly displayed:

INVALID CHAN — This message indicates that the channel is not a valid measurement
channel. The following actions will cause this error:

, , , and , key in the three-digit channel you want to select.

• Trying to close a non-measurement channel, such as a backplane isolation channel,
a channel that sets the pole mode, or a channel that cannot be internally connected
to the DMM.

• Trying to close an amps channel while on a non-amps function. The DCI or ACI
function must be selected in order to close an amps channel.

• Trying to close a paired-channel while on a 4-wire function. For the Model 7700,
channels 1 through 10 are paired to channels 11 through 20 for a 4-wire function.
If, for example, you try to close channel 12 while on the Ω4 function, the
INVALID CHAN error will occur.

• Trying to close a switching module channel that does not exist.

Figure 2-4

System channel operation — specifying measurement channel to close

CLOSEOPEN

CLOSE:SINGLE

CLOSE CH: XXX

Press CLOSE key

Display SINGLE option
and press ENTER

Specify channel number (XXX)
and press ENTER

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-11

TOO SMALL or TOO LARGE — These messages also indicate an invalid channel. TOO
SMALL indicates that the specified channel and any other lower numbered channel is
invalid. TOO LARGE indicates that the specified channel and any other higher numbered
channel is invalid.

OPEN key (ALL menu option)

The ALL menu option of the OPEN key opens all channels for all switching modules
installed in the Model 2750 (Figure 2-5). For example, if a Model 7700 switching module
is installed in slot 1, OPEN: ALL will open all measurement channels (101 to 120, 121,
and 122), the backplane isolation channels (124 and 125) and the 2-pole/4-pole channel
(123). Figure 2-2 shows the backplane isolation channels and the 2-pole/4-pole channel
for the Model 7700.

Perform the following steps to open all channels:

1. Press the OPEN key to display “OPEN: ALL.”

2. Press OPEN a second time (or press ENTER) to open all channels.

NOTE Opening the system channel disables Ratio or Channel Average. Ratio and

Channel Average operation are covered in Section 5.

Figure 2-5

System channel operation — opening all channels in mainframe

CLOSEOPEN

OPEN: ALL

Press OPEN key

Display ALL option
and press OPEN again

2-12 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Remote programming — system channel control commands

The commands to close and open the system channel are listed in Table 2-1. When a
system channel reading is returned, the system channel number will be included in the
data string if the CHANnel data element is selected. The FORMat:ELEMents command is
used to specify the data elements to be included in the data string (see FORMat commands
in Section 14).

Table 2-1

System channel control commands

Commands Description Ref

ROUTe:CLOSe <clist> Specify one measurement channel to close. a
ROUTe:CLOSe:STATe? <clist> Query closed channels in specified list

(1 = closed).

ROUTe:CLOSe? Returns a <clist> of closed measurement

channels.

ROUTe:OPEN:ALL Open all channels, and disable ratio and channel

average.

Channel list parameter:

<clist> = (@SCH)

where: S = Mainframe slot number (1, 2, 3, 4 or 5)

CH = Switching module channel number (must be 2 digits)

Examples: (@101) = Slot 1, Channel 1

(@101, 203) = Slot 1, Channel 1 and Slot 2, Channel 3
(@101:110) = Slot 1, Channels 1 through 10

b

c

d

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-13

Reference:

a. ROUTe:CLOSe <clist>

This command functions the same as the front panel CLOSE key (SINGLE menu
option) to select the system channel. Only one measurement channel can be
specified in the <clist>.

Trying to close an invalid channel (such as a non-measurement channel) with this
command will result in error -222 (Parameter data out of range).

b. ROUTe:CLOSe:STATe? <clist>

This query returns a “0” (open) or “1” (closed) for every measurement channel
specified the <clist>. For example, assume <clist> = (@101, 104, 107, 102). The
response message “0, 0, 1, 0” indicates that channel 107 is closed.

The state of non-measurement channels cannot be checked with this command.

c. ROUTe:CLOSe?

This query command returns a <clist> of closed measurement channels, including
paired channels for 4-wire functions.

This query command will not return non-measurement channels, such as
backplane isolation channels and the pole-mode channel.

d. ROUTe:OPEN:ALL

This command functions the same as the front panel OPEN key (ALL menu
option). It simply opens all channels (including non-measurement channels)
installed in the mainframe.

Remote programming example (system channel operation)

The following example assumes a Model 7700 installed in slot 1, and the Ω4 function of
the Model 2750 is selected. This command sequence connects channel 101 and its paired
channel (111) to DMM Input and Sense as shown in Figure 2-2.

ROUT:OPEN:ALL ' Open all channels.
ROUT:CLOS (@101) ' Close channels 101, 111, 123,

' 124 and 125.

2-14 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Non-amp and non-measure switching modules

There are Keithley switching modules that do not support current measurements and there
are modules that do not support any measurements at all.

Non-amps module — With an amps function selected (DCI or ACI), system channel
operation cannot be used to close channels on that module.

Non-measure module — For front panel operation, system channel operation cannot be
used to close channels. For remote programming, system channel operation can be used,
but only the one specified channel will close. All other channels on the module will open.

Non-amps switching modules

NOTE Presently, non-amps Keithley modules include the Models 7701, 7703, 7706,

7707, 7708, and 7709. You can check the Keithley website (www.keithley.com)
for new modules.

A non-amp module does not support amps measurements. System channel operation
cannot be used to close channels while an amps function (DCI or ICI) is selected.

If an amps function (DCI or ACI) is selected and you attempt to close a system channel,
the message “NO AMPS CHAN” will be displayed briefly. For remote programming,
error -222 (Parameter data out of range) is generated. Example:

SYST:PRES ‘ Restores system preset defaults.
SENS:FUNC ‘CURR:DC’ ‘ Selects DCI function.
ROUT:CLOS (@101) ‘ Attempts to close system channel 101 – Generates

‘ error -222.

If a system channel is already closed and you attempt to select the DCI or ACI function,
the message “INVALID FUNC” will be displayed briefly. For remote programming,
error -221 (Settings conflict) is generated. Example:

SYST:PRES ‘ Restores system preset defaults.
ROUT:CLOS (@101) ‘ Close system channel 101.
SENS:FUNC ‘CURR:DC’ ‘ Attempts to select DCI function – Generates

‘ error -221.

Making amps measurements — In order to perform amps measurements, you must use
the front panel inputs of the 2750 mainframe. You can still use the non-amps module for
other aspects of the test, but you must use multiple channel operation to close channels.
Example:

NOTE In order to use the front panel inputs, make sure the INPUT switch is in the out

(F) position.

SYST:PRES ‘ Restores system preset defaults.
ROUT:MULT:CLOS (@101) ‘ Closes channel 101.
ENS:FUNC ‘CURR:DC’ ‘ Selects DCI function – Legal operation.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-15

Non-measure switching modules

NOTE Presently, non-measure Keithley modules include the Models 7705, 7711, and

7712. You can check the Keithley website (www.keithley.com) for new modules.

Keep the following in mind when using an non-measure module:

• For a non-measure card, no channels are connected to the internal DMM (the
channels cannot be connected to the backplane).

• Multiple channel operation should be used to close channels on a non-measure
module. For remote operation, the ROUT:MULT commands are used to close
channels.

• Front panel system (single) channel operation cannot be used to close channels on
a non-measure module. For front panel operation, system channel operation will
cause message “NO MEAS CARD” to be displayed.

• A non-measure module may have open/close operations that are specific only to
that module. Refer to the appropriate module manual (packing list) for details on
operation.

• In order to perform measurements, you must use the front panel inputs of the 2750
mainframe. You can still use the non-measure module to control other operations.

2-16 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Multiple channel operation

The capability to individually control channels provides you with added flexibility in how
you use a switching module. For example, assume you want to route a signal into channel
1 and out channel 20 of a Model 7700 switching module. You would do this by closing
channels 1, 20, and 23. If you open channels 24 and 25, you will isolate the input signal
from the DMM of Model 2750.

Multiple channel operation allows any channel (or channels) in the test system to be
closed or opened. It allows more than one measurement channel to be closed at the same
time. It also allows individual control of non-measurement channels, such as backplane
isolation channels. Multiple channel operation should only be performed by experienced
test system engineers.

WARNING Careless multiple channel operation could create an electric shock

hazard that could result in severe injury or death. Improper operation
can also cause damage to the switching modules and external circuitry.
Multiple channel operation should be restricted to experienced test
engineers who recognize the dangers associated with multiple channel
closures.

NOTE Multiple channel operation cannot be used to perform thermocouple

temperature measurements using the internal or external reference junction. The
simulated reference junction will instead be used and the integrity of the
temperature reading will be questionable (“ERR” annunciator turns on). See

“Temperature measurements,” page 3-35, for details.

Some other key points for multiple channel operation include the following:

• Closing a channel using multiple channel operation has no affect on other closed
channels. Whatever channels were previously closed, remain closed.

• A channel closed using multiple channel operation is not displayed on the
Model 2750. Also, the CHAN annunciator does not turn on when a channel is
closed.

• Opening a channel using multiple channel operation has no affect on other closed
channels. Only the specified channel opens.

NOTE Use the VIEW option of the CARD menu to display closed channels (see “CARD

menu,” page 2-29).

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-17

Controlling multiple channels

WARNING When using multiple channel operation, you must be very careful

when switching hazardous voltages. If you inadvertently close the
wrong channel(s), you could create a shock hazard and/or cause
damage to the equipment.

Most switching modules use latching relays. That is, closed channels
remain closed when the Model 2750 is turned off. Never handle a
switching module that is connected to an external source that is turned
on. Turn off all power sources before (1) making or breaking
connections to the module, and (2) installing (or removing) the module
into (or out of) the Model 2750.

Avoiding corrupt measurements

Aside from the safety issues, improper use of multiple channel operation can result in
corrupt measurements. For example, assume two Model 7700s installed in slots 1 and 2,
and a 2-wire function selected. If you use multiple channel operation to close channels 201
and 225, you will connect the input at channel 201 to the DMM for measurement.

If you then use system channel operation to close channel 101, channel 125 will also close
to connect the input at channel 101 to the DMM. You now have two input channels (101
and 201) connected to DMM Input at the same time, inviting all sorts of problems.

The above problem can be avoided by opening channels 201 and/or 225 before closing
channel 101 (and 125) as demonstrated by the following sequence:

1. Multiple channel operation — Close channels 201 and 225 for connection to
DMM.

2. Multiple channel operation — Open channels 201 and/or 225 to disconnect from
DMM.

3. System channel operation — Close system channel 101 to connect to DMM.

2-18 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

CLOSE key (MULTI menu option)

The MULTI menu option for the CLOSE key can be used to close any individual channel
in the mainframe (Figure 2-6). Perform the following steps to close a channel:

NOTE Channels closed by the MULTI option of the CLOSE key are not displayed. Use

the VIEW option of the CARD menu to display closed channels (see “CARD

menu,” page 2-29).

1. Press the CLOSE key and then use the

 or  key to display the “CLOSE:MULTI”

message.

2. Press ENTER to display the prompt to close a channel (CLOSE MLT:XXX).

3. Using

, , , and , key in the three-digit channel you want to select.

4. Press ENTER to close the channel.

An invalid channel cannot be closed. The error messages associated with system channel
operation also apply to multiple channel operation.

Figure 2-6

Multiple channel operation — specifying a channel to close

CLOSEOPEN

CLOSE:MULTI

CLOSE MLT:XXX

Press CLOSE key

Display MULTI option
and press ENTER

Specify channel number
(XXX) and press ENTER

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-19

OPEN key

The OPEN key has two options to open channels: ALL and MULTI. The ALL option
simply opens all channels in the mainframe. The MULTI option opens only the specified
channel. All other closed channels remain closed. Figure 2-7 summarizes OPEN key
operation.

OPEN: ALL — Perform the following steps to open all channels in the mainframe:

1. Press the OPEN key to display “OPEN: ALL.”

2. Press OPEN again (or press ENTER) to open all channels.

OPEN: MULTI — Perform the following steps to open only the specified channel:

1. Press the OPEN key. The “OPEN: ALL” message will be displayed.

2. Press the

3. Press ENTER to display the prompt to open a channel (OPEN MLT:XXX).

4. Using

5. Press ENTER to open the channel.

NOTE If the channel you open using OPEN: MULTI is the system channel (channel

 or  key to display the “OPEN: MULTI” message.

, , , and , key in the three-digit channel you want to select.

number displayed on the Model 2750), the channel will open, but the system
channel number will still be displayed (see “Multiple channel operation

anomalies,” page 2-22).

Figure 2-7

Multiple channel operation — opening one or all channels

Press OPEN key

Display MULTI option
and press ENTER

Specify channel number
(XXX) and press ENTER

Display ALL option
and press OPEN again

OPEN: ALL

CLOSEOPEN

OPEN: MULTI

OPEN MULTI:XXX

2-20 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Remote programming — Multiple channel control commands

The commands to close and open the system channel are listed in Table 2-2.

Table 2-2

Multiple channel control commands

Commands Description Ref

ROUTe:MULTiple:CLOSe <clist> Specify one or more channels to

close.

ROUTe:MULTiple:OPEN <clist> Open channels specified in list. Unlisted

channels not affected.
ROUTe:OPEN:ALL Open all channels. c
ROUTe:MULTiple:CLOSe? Returns a <clist> of all closed channels. d
ROUTe:MULTiple:CLOSe:STATe?

<clist>

Query closed channels in specified list

(1 = closed).

Channel list parameter:

<clist> = (@SCH)

where: S = Mainframe slot number (1, 2, 3, 4 or 5)

CH = Switching module channel number (must be 2 digits)

Examples: (@101) = Slot 1, Channel 1

(@101, 203) = Slot 1, Channel 1 and Slot 2, Channel 3
(@101:110) = Slot 1, Channels 1 through 10

Reference:

a. ROUTe:MULTiple:CLOSe <clist>

This command functions like the front panel CLOSE key (MULTI menu option) to
close channels. When you send this command to close the channels specified in the
<clist>, only those listed channels will close. Channels not specified are not
affected, and channel pairing is disabled.

a

b

e

NOTES Channels closed by ROUT:MULT:CLOS are not displayed.

The ROUT:MULT:CLOS command cannot be used to perform
thermocouple temperature measurements using the internal or
external reference junction. The simulated reference junction will
instead be used and the integrity of the temperature reading will be
questionable (“ERR” annunciator on). See “Temperature

measurements,” page 3-35, for details.

NOTE For RS-232 operation (and in some cases, GPIB operation), *OPC

or *OPC? should be used with :ROUT:MULT:CLOS if the <clist> is
large. Details on *OPC and *OPC? are provided in Section 12.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-21

b. ROUTe:MULTiple:OPEN <clist>

With this command, you can open one or more switching module channels. When
you send this command to open the channels specified in the <clist>, only those
listed channels will open. Channels not specified are not affected.

NOTE For RS-232 operation (and in some cases, GPIB operation), *OPC

or *OPC? should be used with :ROUT:MULT:OPEN if the <clist>
is large. Details on *OPC and *OPC? are provided in Section 12.

c. ROUTe:OPEN:ALL

This command functions the same as the front panel OPEN key (ALL menu
option). It simply opens all channels (including non-measurement channels) in the
mainframe.

d. ROUTe:MULTiple:CLOSe?

This query command returns a <clist> of all closed channels, including
non-measurement channels and paired channels for 4-wire functions.

e. ROUTe:MULTiple:CLOSe:STATe? <clist>

This query returns a “0” (open) or “1” (closed) for every channel specified in the
<clist>. It is valid for both measurement and non-measurement channels.

For example, assume channel 125 is closed, and you use this command to query
channels 101, 104, and 125 (<clist> = (@101, 104, 125)). The response message
returns “0, 0, 1” to indicate that channels 101 and 104 are open, and channel 125 is
closed.

Remote programming example (multiple channel operation)

The following example assumes a Model 7700 installed in slot 1. This command sequence
connects channel 101 to channel 111 (through channel 123). Note that these two closed
channels will be internally isolated from the DMM since the backplane isolation channels
(124 and 125) will be open.

NOTE The following example can be run from the KE2700 Instrument Driver using the

example named “CloseChannels” in Table H-1 of Appendix H.

ROUT:OPEN:ALL ' Open all channels.
ROUT:MULT:CLOS (@101,111,123) ' Close channels 101, 111, and 123.

When finished with multiple channel operation it is a good, safe practice to open all chan­nels (ROUT:OPEN:ALL).

2-22 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Multiple channel operation anomalies

• Anomaly #1 — When you use multiple channel operation to open the system
channel, the channel will open but the system channel number will still be
displayed on the Model 2750. For details, see “Anomaly #1 example — wrong

channel displayed.”

• Anomaly #2 — For a 4-wire function, you can use multiple channel operation to
open the paired channel. If you then use system channel operation to again select
the already closed system channel, it will not re-close the paired channel. For
details, see “Anomaly #2 example — opening the paired channel.”

NOTE The following anomaly examples assume a Model 7700 installed in slot 1.

Anomaly #1 example — wrong channel displayed

The following example closes channel 102 and connects it to the DMM Input. However,
the Model 2750 will not display the measurement channel that is closed. It will display
channel 101 instead of channel 102.

1. Use the ALL option for the OPEN key to open all channels in the mainframe.

Remote programming:

2. Press the  key to close (and display) channel 101. This closes channel 101 (which
is the system channel) and channel 125 to connect it to the DMM Input
(Figure 2-1).

Remote programming: ROUT:CLOS (@101)

3. Use the MULTI option for the CLOSE key to close channel 102. The system
channel is not affected. Channels 101, 102, and 125 are now closed.

Remote programming: ROUT:MULT:CLOS (@102)

4. Use the MULTI option for the OPEN key, open channel 101. Even though channel
101 is still being displayed on the Model 2750, it is channel 102 that is actually
connected to the DMM Input (channels 102 and 125 closed).

Remote programming: ROUT:MULT:OPEN (@101)

ROUT:OPEN:ALL

To correctly display the channel that is closed (channel 102) repeat step 1 above to open
all channels, and then use the  key or the ROUT:CLOS (@102) command to close (and
display) channel 102. This closes channel 102 (which is the system channel) and channel
125 to connect it to the DMM Input.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-23

Anomaly #2 example — opening the paired channel

Assume 4-wire connections to a 1kΩ resistor using channels 1 and 11 of the Model 7700
switching module. Also assume the Ω4 function is selected. The following procedure
demonstrates how careless multiple channel operation can cause an overflow reading even
though everything else from the front panel “looks right.”

1. Use the ALL option for the OPEN key (OPEN: ALL) to open all channels in the
mainframe.

Remote programming: ROUT:OPEN:ALL

2. Press the  key to close (and display) channel 101. The following channels close
(see Figure 2-2):

• Channel 101 (system channel).

• Channel 125 (connects channel 101 to DMM Input).

• Channel 111 (paired channel for 4-wire measurements).

• Channel 124 (connects channel 111 to DMM Sense).

• Channel 123 (isolates channel 101 from channel 111).

The Model 2750 will display the 1kΩ reading for system channel 101.

Remote programming:

3. Using the MULTI option for the OPEN key, open channel 111. This opens the
connection to DMM Sense and causes an OVRFLW reading. Keep in mind that
channel 101 is still closed and displayed as the system channel.
Remote programming: ROUT:MULT:OPEN (@111)

4. In an attempt to clear the overflow reading problem, use the SINGLE option of the
CLOSE key to again close channel 101. You might think that this will again close
channel 111 to reconnect it to DMM Sense. However, that is not the case. Since
channel 101 is still the system channel, selecting it again in this manner is a “no
action.” Channel 111 does not close.
Remote programming: ROUT:CLOS (@101)

ROUT:CLOS (@101)

A simple way to resolve the above problem is to repeat step 1 to open all channels, and
then repeat step 2 to close channel 101. All the listed channels in step 2 will close to make
the 4-wire connection to the 1kΩ resistor.

2-24 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Dual independent multiplexers

Using multiple channel operation, any multiplexer switching module can be configured as
two independent multiplexers. For example, the Model 7700 is normally used as a single
1 × 20 multiplexer, but it can also be configured as two 1 × 10 multiplexers.

NOTE Thermocouple temperature measurements using the internal or external

reference junction cannot be performed when using multiple channel operation
to connect an input channel to the DMM. The simulated reference junction will
instead be used resulting in invalid readings (“ERR” annunciator turns on). See

“Temperature measurements,” page 3-35, for details.

A multiplexer switching module is configured as two multiplexers by using multiple
channel operation to close the 2-pole/4-pole relay. The Model 7700 is configured as two
independent multiplexers by closing channel 23. As shown in Figure 2-8, the closed
position of channel 23 isolates Multiplexer A (channels 1 through 10) from Multiplexer B
(channels 11 through 20).

For the dual multiplexer configuration, only Multiplexer A channels can be internally
connected to the DMM of the Model 2750. For the Model 7700, closing channel 25 allows
channels 1 through 10 to be measured by the DMM.

When using the dual multiplexer configuration, the sense backplane isolation relay must
be kept open to isolate Multiplexer B channels from the sense terminals of the DMM. For
the Model 7700, channel 24 must be kept open (Figure 2-8).

Figure 2-8

Dual multiplexer configuration (Model 7700)

HI

Ch 1

LO

Multiplexer A

(1x10)

Multiplexer B

(1x10)

Channels

HI

LO

HI

LO

Channels

HI

LO

2–9

Ch 10

(Closed)

Ch 11

12–19

Ch 20

Ch 25

Ch 23

Ch 24

For the dual multiplexer configuration,
Ch 23 must be closed, and Ch 24 must
remain open.

HI

Input

LO

To
Model 2750
DMM

HI

Sense

LO

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-25

Dual multiplexer application

This application demonstrates how to use the Model 7700 as a dual multiplexer to bias and
measure 10 DUT. An external source powers the DUT, while the DMM of the Model 2750
measures the output of the DUT. To prevent overloading of the external source, each DUT
is powered (and measured) separately.

Figure 2-9 shows the connections for this application. The external source is connected to

the Sense terminals of the switching module, and DUT is connected to channels 1 through

10. Channels 11 through 20 are used to connect external power to each DUT.

For this application, the 2-pole/4-pole relay and backplane isolation relays of the switch­ing module are to be controlled as follows:

• Closing channel 23 connects the External Source to DUT via channels 11 through

20. Closing channel 23 also isolates measure channels (1 through 10) from the
source channels (11 through 20). This channel must remain closed while testing
DUT.

• Opening channel 24 isolates the external source from the backplane of the
Model 2750. This channel must remain open while testing DUT.

• Closing channel 25 connects an input channel (1 through 10) to the DMM.

In Figure 2-9, channels 1 and 11 are closed to test DUT 1. A more detailed view of the test
for DUT 1 is shown in Figure 2-10. The test for the other DUTs is similar except that
different source and measure channels are closed. Closed channels for each DUT test are
listed as follows:

Tested
device Closed channels

DUT 1 1, 11, 23 and 25 DUT 6 6, 16, 23 and 25
DUT 2 2, 12, 23 and 25 DUT 7 7, 17, 23 and 25
DUT 3 3, 13, 23 and 25 DUT 8 8, 18, 23 and 25
DUT 4 4, 14, 23 and 25 DUT 9 9, 19, 23 and 25
DUT 5 5, 15, 23 and 25 DUT 10 10, 20, 23 and 25

NOTE Do not use this application to measure the temperature of the DUT using a

thermocouple with the INTernal or EXTernal reference junction selected. The
SIMulated reference junction will instead be used resulting in invalid readings.
The “ERR” annunciator will turn on to indicate that the integrity of the
temperature reading is questionable.

Tested

device Closed channels

2-26 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Figure 2-9

Dual multiplexer application connections

Model 2750

Model 7700 Switching Module

H1

External

Source

DUT

1

DUT

2

Sense

LO

H1

LO

H1

LO

Ch 1

Ch 2

DUT

10

H1

LO

H1

LO

H1

LO

H1

LO

Ch 10

Ch 11

Ch 12

Ch 20

Ch 25

Ch 23

(Closed)

Ch 24

HI

Input

LO

DMM

HI

Sense

LO

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-27

Figure 2-10

Testing DUT 1

Model 2750

Model 7700 Switching Module

HI

External

Source

DUT

1

Sense

LO

HI

Ch 1

LO

Ch 25

Slot 1

HI

Input

LO

DMM

HI

Sense

LO

DMM

HI

Ch 11

LO

Mutliple channel operation:
Open all channels
Close channel 123
Close channel 125
Close channel 101
Close channel 111

Ch 23

(Closed)

External

Source

Equivalent Circuit

Ch 24

DUT

1

Test procedure:

NOTES The following test procedure assumes a Model 7700 switching module installed

in slot 1 of the mainframe.

The procedure assumes that the instrument is operating in the continuous
measurement (triggering) mode (see “Defaults and user setups,” page 1-21).

Do not use the following procedure to perform thermocouple temperature
measurements with the INTernal or EXTernal reference junction selected. The
SIMulated reference junction will instead be used resulting in invalid readings.
The “ERR” annunciator will turn on to indicate that the integrity of the
temperature reading is questionable.

2-28 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

1. Open all channels. For most switching modules, channels remain closed after the
Model 2750 is turned off. Therefore, it is good, safe practice to open all channels at
the start and end of the test.

Front panel operation: Press OPEN > Display ALL > Press OPEN

Remote programming:

ROUT:OPEN:ALL

2. Close channels 23 and 25.

Front panel operation: Press CLOSE > Select MULTI > Key in 123 >

Press ENTER

Press CLOSE > Select MULTI > Key in 125 >
Press ENTER

Remote programming:

ROUT:MULT:CLOS (@123,125)

3. Close channels 1 and 11 to connect DUT #1 to the DMM and bias supply.

Front panel operation: Press CLOSE > Select MULTI > Key in 101 >

Press ENTER

Press CLOSE > Select MULTI > Key in 111 >
Press ENTER

Remote programming:

ROUT:MULT:CLOS (@101,111)

4. Measure DUT #1.

Front panel operation: Take reading from display

Remote programming:

DATA?

5. Open channels 1 and 11.

Front panel operation: Press OPEN > Select MULTI > Key in 101 >

Press ENTER

Press OPEN > Select MULTI > Key in 111 >
Press ENTER

Remote programming:

ROUT:MULT:OPEN (@101,111)

6. Modify steps 3, 4, and 5 to test DUT #2. That is, close channels 2 and 12, measure
DUT #2, and then open channels 2 and 12.

7. Test the remaining eight DUT in a similar manner. That is, close the appropriate
channels for the DUT, make the measurement, and then open the channels.

8. After the last DUT is tested, repeat step 1 to open all channels.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-29

Identifying installed modules and viewing closed channels

On power-up, the model numbers of installed switching modules are displayed briefly.
While in the normal display state, red slot indicators on the right side of the display
indicate which slots have a switching module or pseudocard installed.

NOTE If a Model 7700, 7701, 7702, 7703, 7705, 7708, or 7709 switching module is

removed while the Model 2750 is on, the slot indicator for that slot will remain
on, and the instrument will operate as if the module is installed. That is, the
Model 2750 will operate as if the pseudocard is installed.

NOTE If a Model 7706 or 7707 is removed while power is on, error +523 (“Card

hardware error”) will occur, and the module will be removed from the system.

NOTE In general, it is not recommended to install or remove switching modules with

the power on.

CARD menu

The CARD menu identifies the switching modules installed in the mainframe, and is used
for the following operations:

• Configure digital inputs and outputs, and analog outputs for switching modules that
have one or more of those capabilities (i.e., Models 7706 and 7707).

• View the analog input channels that are presently closed. Also, read digital input
and output ports, and analog output values for switching modules that have one or
more of those capabilities.

Menu navigation keys — Once in the menu structure, the manual range keys (
and the cursor keys (
parameter values. With the desired item, option or setting displayed, press the ENTER key
to select it. You can cancel a pending selection (and exit the menu structure) by pressing
the EXIT key.

Press the SHIFT key and then the CARD key to display the CARD menu. The Card menu
tree is shown in Figure 2-11. The items and options of the menu are explained as follows:

NOTE Identifying installed modules — If you simply want to identify installed modules

or pseudocards, select CONFIG or VIEW and use the
slot. While in the menu structure, the slot indicator for the selected slot will be
on. The other indicators will be off. When finished, press EXIT.

 and ) are used to display menu items and options, and set

 or  key to check each

 and )

2-30 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

CARD: CONFIG — This menu item is used to configure switching modules. The
channels of the Model 7700 switching module and other similar type modules do not need
to be configured.

SLOTX: 77xx — Use to configure the switching module in Slot X (where X = 1, 2, 3, 4,
or 5). If configuration is not necessary, the instrument will exit from the menu when
ENTER is pressed.

NOTE For switching modules that require configuration, refer to the packing list that

was shipped with each module.

CARD: VIEW — This menu item is used to view all analog input channels that are
presently closed. These include both measurement and non-measurement channels.

The channels are built into a string that scrolls the display. Four dots identify the end of the
string. Model 7700 example (Slot 1) — Assume the Ω4 function is selected and system
channel 101 is closed. The following string will scroll across the display:

101, 111, 123, 124, 125 . . . .

Channels 101 and 111 are the paired channels for the 4-wire measurement. Channel 123 is
the 4-pole relay setting, and channels 124 and 125 connect input and sense to the DMM of
the Model 2750 (Figure 2-2).

NOTE Some switching modules have analog outputs, digital inputs, and/or digital out-

puts. The values for these channels are also displayed from the VIEW menu item.
For details on a particular switching module, refer to the packing list that was
shipped with each module.

SLOTX: 77xx — Use to scroll the closed channels and channel settings (if applicable) for
the switching module in Slot X (where X = 1, 2, 3, 4, or 5).

Scrolling speed — The scrolling speed of the channel string is adjustable, or can be

paused. The

 key slows down scrolling speed and the  key speeds it up. The ENTER

key pauses scrolling. Press ENTER a second time to resume scrolling.

Exiting VIEW —

key will also exit VIEW, but it will also perform the operation associated with the key. For
example, pressing Ω2 will exit VIEW, and select the Ω2 function.

To exit from VIEW, press the EXIT key. Pressing an instrument setting

NOTE When a command is received while the display is scrolling, the instrument exits

from the CARD menu and the command is executed.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-31

Figure 2-11

CARD menu tree

SHIFT

CARD

CONFIG

SLOT1: 77XX SLOT5: 77XX

77XX = Model number of installed
switching module.

SLOT1: 77XX

Scrolls

Channels

Switching module queries (remote operation)

For remote operation there are commands to identify installed switching modules and
channels that are closed. There are also commands to acquire general information about
the installed modules.

*OPT?

For remote operation, the *OPT? command can be used to determine which switching
modules (or pseudocards) are installed in the Model 2750. For example, assume a
Model 7700 is installed in slot 1, a Model 7706 is installed in slot 2 and the other slots are
empty. After sending *OPT? and addressing the Model 2750 to talk, the following
response message will be sent to the computer:

7700, 7706, NONE, NONE, NONE

VIEW

SLOT5: 77XX

Scrolls

Channels

2-32 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

ROUTe:CLOSe?
ROUTe:MULTiple:CLOSe?
ROUTe:MULTiple:CLOSe:STATe? <clist>

These query commands are used to determine closed switching module channels.

ROUT:CLOS? is used to return a list of closed measurement channels including the paired
channel for 4-wire measurements. It will not return non-measurement channels. For
details, see Table 2-1 and related reference information.

ROUT:MULT:CLOS? is used to return all closed channels (measurement and non­measurement). For details, see Table 2-2 and related reference information.

ROUT:MULT:CLOS:STAT? is used to return the state (open or closed) of each specified
channel. A “0” is returned for an open channel, and a “1” is returned for a closed channel.
For details, see Table 2-2 and related reference information.

SYSTem:CARD commands

There is a series of SYSTem:CARD commands that can be used to acquire the following
information about a switching module installed in the Model 2750:

• Return the serial number and firmware revision.

• Determine the maximum allowable voltage.

• Determine if the module supports multiplexer or isolated channels.

• Determine if the module has built-in temperature sensors for internal cold junction,
thermocouple temperature measurements.

• Determine which channels are used for volts/2-wire measurements and which are
used for amps.

• Determine which channels are used for analog or digital output.

• Determine the totalizer channel (Model 7706 only).

The SYSTem:CARD commands are covered in Table 15-7.

Relay closure count

The Model 2750 keeps an internal count of the number of times each module relay has
been closed. The total number of relay closures are stored in EEPROM on the card. This
count will help you determine if and when any relays require replacement (see module
contact life specifications).

Relay closures are counted only when a relay cycles from open to closed state. If you send
multiple close commands to the same channel without sending an open command, only
the first closure will be counted.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-33

Relay closure count can only be read via remote operation. The commands are
summarized in Table 2-3. Details follow the table.

Table 2-3

Relay closure count commands

Commands Description Default

ROUTe:CLOSe:COUNt? <clist> Query close count for specified

channels.

ROUTe:CLOSe:COUNt:INTerval <NRf> Set count update interval in minutes

Note

(10 to 1440).

ROUTe:CLOSe:COUNt:INTerval? Query relay count update interval.

Channel list parameter:

<clist> = (@SCH)

where: S = Mainframe slot number (1, 2, 3, 4 or 5)

CH = Switching module channel number (must be 2 digits)

Examples: (@101) = Slot 1, Channel 1

(@101, 203) = Slot 1, Channel 1 and Slot 2, Channel 3
(@101:110) = Slot 1, Channels 1 through 10

Note: Relay count interval set to 15 minutes at the factory. SYSTem:PREset and *RST have no effect on the

set interval.

NOTE The relay closure count can be reset to zero. For details, see Model 2750 Service

Manual, “Plug-in module relay closure count.”

Reading relay closure count

To determine the closure count of specific channels, send this query via remote:

ROUTe:CLOSe:COUNt? <clist>

Here, <clist> is the summary of channels. For example, to determine the closure count of
channels 1 and 4 of a module in slot 1, the following query would be sent:

ROUT:CLOS:COUN? (@101,104)

The following query would determine the closure count of slot 1 module channels 1
through 10:

ROUT:CLOS:COUN? (@101:110)

2-34 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Setting count update interval

Relay closure counts are updated in temporary RAM every time a channel is closed
regardless of how it was closed: by an SCPI command, front panel control, or during a
scan. These counts are permanently written to the EEPROM on the card only at a user-set
time interval (which is initially set to 15 minutes at the factory), or whenever the counts
are queried. Valid intervals (set in integer number of minutes) are between 10 and 1440
minutes (24 hrs).

The lower the interval, the less chance there is of losing relay counts due to power
failures. However, writing to the EEPROM more often may reduce scanning throughput.
The higher the interval, the less scanning throughput is reduced, but more relay counts
may be lost in the event of a power failure.

NOTE If the Model 2750 is turned off before the updated count is written to EEPROM,

the relay counts will be lost. It is good practice to add the ROUT:CLOS:COUN?
<clist> command at the end of a program to manually update the count.

To set the count update interval, send this command:

ROUTe:CLOSe:COUNt:INTerval <NRf>

where; <NRf> = 10 to 1440 (minutes)

For example, to set the interval to 30 minutes, send this command:

ROUT:CLOS:COUN:INT 30

Model 7700 switching module

NOTE Connection and wiring procedures for the Model 7700 are to be performed by

qualified service personnel. This information is provided in Appendix B
(Model 7700 Connection Guide).

Switching module capabilities

Channels 1 through 20 — The Model 7700 can multiplex one of 20 2-pole signals, or one
of 10 4-pole signals into the input of the Model 2750.

Channels 21 and 22 — The Model 7700 can multiplex one of two 2-pole current signals
into the input of the Model 2750.

Model 2750 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-35

CAUTION To prevent damage to the Model 7700 switching module, do not exceed

these maximum signal levels:

Channels 1-20: 300VDC or 300V RMS (425V peak) for AC

waveforms, 1A switched, 60W, 125VA

Channels 21, 22: 60VDC or 30V RMS, 3A switched, 60W, 125VA

NOTE System channel operation – Of the 22 measurement channels, only one channel

(or channel pair) can be closed at the same time. When you close a channel (or
channel pair), all other measurement channels will open. The user has no
control of channels 23, 24, and 25. The open/close state of these channels are
determined by the selected function.

The Model 7700 has six temperature transducers to monitor the cold junction temperature
at the screw terminals. For temperature measurements, this internal reference junction
allows thermocouples to be connected directly to the screw terminals of the module.

When the Model 2750 is on the DCV, ACV, Ω2, CONT, Ω4, FREQ, PERIOD, or TEMP
function, channels 1 through 20 are available. When on a current function (DCI or ACI),
channels 21 and 22 are the only available channels.

The Model 7700 can accommodate 4-wire measurements by using channel pairs. Primary
channels 1 through 10 become paired to channels 11 through 20. For example, with the Ω4
function selected, channel 1 becomes paired to channel 11. For example, when you close
channel 1, channel 11 will also close.

The 2-wire functions include DCV, ACV, DCI, ACI, Ω2, CONT, FREQ, PERIOD, and
TEMP (thermocouple and thermistor). The 4-wire functions/operations include Ω4,
TEMP (4-wire RTD), RATIO, and CH AVG (ratio and channel average are covered in

Section 5).

With a 4-wire function/operation selected, channels are paired as follows:

• CH1 and CH11 • CH6 and CH16

• CH2 and CH12 • CH7 and CH17

• CH3 and CH13 • CH8 and CH18

• CH4 and CH14 • CH9 and CH19

• CH5 and CH15 • CH10 and CH20

2-36 Close/Open Switching Module Channels Model 2750 Multimeter/Switch System User’s Manual

Schematic diagram

The simplified schematic diagram of the Model 7700 is shown in Figure 2-12. Channels 1
through 20 are used for all measurements except amps. Channels 21 and 22 are used for
amps only.

There are two backplane relays (channels 24 and 25) to connect the input channel(s) to the
backplane of the Model 2750. With a 2-wire function (except amps) selected, channel 25
will close, and with a 4-wire function selected, both channels 24 and 25 will close.

There is a 2-pole/4-pole relay (channel 23) between channels 1-10 and channels 11-20.
When a 2-wire function (i.e., DCV) is selected, channel 23 opens (2-pole position) to
allow any of the 20 channels to be connected to the input backplane.

When a 4-wire function is selected, channel 23 closes (4-pole position) to isolate channels
1 through 10 from channels 11 through 20. With a system channel (1 through 10) closed,
its paired channel (11 through 20) will also close to connect the sense channel to the sense
backplane.

For the two current channels (21 and 22), signal HI and LO are routed directly to the back­plane when the channel is closed.

As shown in Figure 2-12, there are also screw terminals labeled “Input,” “Sense,” and
“Amps.” The Input and Sense terminals are connected to the inputs of channels 24 and 25
(isolation relays). If channels 1 through 20 are not intended to be connected to the internal
DMM, channels 24 and 25 can be controlled independently using multiple channel
operation. The Amps terminals are connected directly to the DMM.