USER’S GUIDE
HP Model 66111A
Fast Transient DC Source
HP Model 66311B
Mobile Communications DC Source
For instruments with Serial Numbers:
HP 66111A: US38460101 and up
HP 66311B: US38440101 and up
HP Part No. 5964-8106
Microfiche No. 5964-8107
Last Update: January 1999
Warranty Information
CERTIFICATION
Hewlett-Packard Company certifies that this product met its published specifications at time of shipment from the
factory. Hewlett-Packard further certifies that its calibration measurements are traceable to the United States
National Bureau of Standards, to the extent allowed by the Bureau’s calibration facility, and to the calibration
facilities of other International Standards Organization members.
WARRANT Y
This Hewlett-Packard hardware product is warranted against defects in material and workmanship for a period of
three years from date of delivery. HP software and firmware products, which are designated by HP for use with a
hardware product and when properly installed on that hardware product, are warranted not to fail to execute their
programming instructions due to defects in material and workmanship for a period of 90 days from date of delivery.
During the warranty period Hewlett-Packard Company will, at its option, either repair or replace products which prove
to be defective. HP does not warrant that the operation for the software firmware, or hardware shall be uninterrupted
or error free.
For warranty service, with the exception of warranty options, this product must be returned to a service facility
designated by HP. Customer shall prepay shipping charges by (and shall pay all duty and taxes) for products
returned to HP for warranty service. Except for products returned to Customer from another country, HP shall pay for
return of products to Customer.
Warranty services outside the country of initial purchase are included in HP’s product price, only if Customer pays
HP international prices (defined as destination local currency price, or U.S. or Geneva Export price).
If HP is unable, within a reasonable time to repair or replace any product to condition as warranted, the Customer
shall be entitled to a refund of the purchase price upon return of the product to HP.
LIMITATION OF WARRANTY
The foregoing warranty shall not apply to defects resulting from improper or inadequate maintenance by the
Customer, Customer-supplied software or interfacing, unauthorized modification or misuse, operation outside of the
environmental specifications for the product, or improper site preparation and maintenance. NO OTHER
WARRANTY IS EXPRESSED OR IMPLIED. HP SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
EXCLUSIVE REMEDIES
THE REMEDIES PROVIDED HEREIN ARE THE CUSTOMER’S SOLE AND EXCLUSIVE REMEDIES. HP SHALL
NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
WHETHER BASED ON CONTRACT, TORT, OR ANY OTHER LEGAL THEORY.
ASSISTANCE
The above statements apply only to the standard product warranty. Warranty options, extended support contacts,
product maintenance agreements and customer assistance agreements are also available. Contact your nearest
Hewlett-Packard Sales and Service office for further information on HP’s full line of Support Programs.
2
Safety Summary
y
The following general safety precautions must be observed during all phases of operation of this instrument.
Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safet
standards of design, manufacture, and intended use of the instrument. Hewlett-Packard Company assumes no
liability for the customer’s failure to comply with these requirements.
GENERAL
This product is a Safety Class 1 instrument (provided with a protective earth terminal). The protective features of
this product may be impaired if it is used in a manner not specified in the operation instructions.
Any LEDs used in this product are Class 1 LEDs as per IEC 825-1.
ENVIRONMENTAL CONDITIONS
This instrument is intended for indoor use in an installation category II, pollution degree 2 environment. It is
designed to operate at a maximum relative humidity of 95% and at altitudes of up to 2000 meters. Refer to the
specifications tables for the ac mains voltage requirements and ambient operating temperature range.
BEFORE APPLYING POWER
Verify that the product is set to match the available line voltage, the correct fuse is installed, and all safety
precautions are taken. Note the instrument’s external markings described under "Safety Symbols".
GROUND THE INSTRUMENT
To minimize shock hazard, the instrument chassis and cover must be connected to an electrical ground. The
instrument must be connected to the ac power mains through a grounded power cable, with the ground wire firmly
connected to an electrical ground (safety ground) at the power outlet. Any interruption of the protective (grounding)
conductor or disconnection of the protective earth terminal will cause a potential shock hazard that could result in
personal injury.
ATTENTION: Un circuit de terre continu est essentiel en vue du fonctionnement sécuritaire de l’appareil.
Ne jamais mettre l'appareil en marche lorsque le conducteur de mise … la terre est d‚branch‚.
FUSES
Only fuses with the required rated current, voltage, and specified type (normal blow, time delay, etc.) should be
used. Do not use repaired fuses or short-circuited fuseholders. To do so could cause a shock or fire hazard.
DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE
Do not operate the instrument in the presence of flammable gases or fumes.
DO NOT REMOVE THE INSTRUMENT COVER
Operating personnel must not remove instrument covers. Component replacement and internal adjustments must be
made only by qualified service personnel.
Instruments that appear damaged or defective should be made inoperative and secured against unintended
operation until they can be repaired by qualified service personnel.
3
SAFETY SYMBOLS
Direct current
Alternating current
Both direct and alternating current
Three-phase alternating current
Earth (ground) terminal
Protective earth (ground) terminal
Frame or chassis terminal
Terminal is at earth potential. Used for measurement and control circuits designed to be
operated with one terminal at earth potential.
Terminal for Neutral conductor on permanently installed equipment
WARNING
Caution
Terminal for Line conductor on permanently installed equipment
On (supply)
Off (supply)
Standby (supply). Units with this symbol are not completely disconnected from ac mains when
this switch is off. To completely disconnect the unit from ac mains, either disconnect the power
cord or have a qualified electrician install an external switch.
In position of a bi-stable push control
Out position of a bi-stable push control
Caution, risk of electric shock
Caution, hot surface
Caution (refer to accompanying documents)
The WARNING sign denotes a hazard. It calls attention to a procedure, practice, or the like,
which, if not correctly performed or adhered to, could result in personal injury. Do not proceed
beyond a WARNING sign until the indicated conditions are fully understood and met.
The CAUTION sign denotes a hazard. It calls attention to an operating procedure, or the like,
which, if not correctly performed or adhered to, could result in damage to or destruction of part
or all of the product. Do not proceed beyond a CAUTION sign until the indicated conditions
are fully understood and met.
4
Declaration Page
Manufacturer’s Name: Hewlett-Packard Company
Manufacturer’s Address: 150 Green Pond Road
declares that the Product
Product Name: a) Dynamic Measurement DC Source
Model Number: a) HP 66311A, 66311B, 66312A, 66111A
DECLARATION OF CONFORMITY
according to ISO/IEC Guide 22 and EN 45014
Rockaway, New Jersey 07866
U.S.A.
b) System DC Power Supply
c) Remote Front Panel
b) HP 6612B, 6611C, 6612C, 6613C, 6614C
c) HP 14575A
conforms to the following Product Specifications:
Safety: IEC 1010-1:1990+A1(1992) / EN 61010-1:1993
EMC: CISPR 11:1990 / EN 55011:1991 - Group 1 Class B
IEC 801-2:1991 / EN 50082-1:1992 - 4 kV CD, 8 kV AD
IEC 801-3:1984 / EN 50082-1:1992 - 3 V / m
IEC 801-4:1988 / EN 50082-1:1992 - 0.5 kV Signal Lines
1 kV Power Lines
Supplementary Information:
The product herewith complies with the requirements of the Low Voltage Directive
73/23/EEC and the EMC Directive 89/336/EEC and carries the CE-marking accordingly.
New Jersey April, 1998 ______
Location Date Bruce Krueger / Quality Manager
European Contact: Your local Hewlett-Packard Sales and Service Office or Hewlett-Packard GmbH,
Department TRE, Herrenberger Strasse 130, D-71034 Boeblingen (FAX:+49-7031-14-3143)
5
Acoustic Noise Information
Herstellerbescheinigung
Diese Information steht im Zusammenhang mit den Anforderungen der
Maschinenläminformationsverordnung vom 18 Januar 1991.
* Schalldruckpegel Lp <70 dB(A)
* Am Arbeitsplatz
* Normaler Betrieb
* Nach EN 27779 (Typprüfung).
Manufacturer's Declaration
This statement is provided to comply with the requirements of the German Sound Emission Directive, from
18 January 1991.
* Sound Pressure Lp <70 dB(A)
* At Operator Position
* Normal Operation
* According to EN 27779 (Type Test).
Printing History
The edition and current revision of this manual are indicated below. Reprints of this manual containing
minor corrections and updates may have the same printing date. Revised editions are identified by a new
printing date. A revised edition incorporates all new or corrected material since the previous printing date.
Changes to the manual occurring between revisions are covered by change sheets shipped with the manual.
In some cases, the manual change applies only to specific instruments. Instructions provided on the change
sheet will indicate if a particular change applies only to certain instruments.
This document contains proprietary information protected by copyright. All rights are reserved. No part of
this document may be photocopied, reproduced, or translated into another language without the prior
consent of Hewlett-Packard Company. The information contained in this document is subject to change
without notice.
Copyright 1998 Hewlett-Packard Company Edition 1 __________December, 1998
6
Table of Contents
Warranty Information 2
Safety Summary 3
Declaration Page 5
Acoustic Noise Information 6
Printing History 6
Table of Contents 7
1 - QUICK REFERENCE 13
The Front Panel - At a Glance 13
The Rear Panel - At a Glance 14
Instrument Configuration 14
Front Panel Number Entry 15
Front Panel Annunciators 16
Immediate Action Keys 16
Front Panel Menus - At a Glance 17
SCPI Programming Commands - At a Glance 18
2 - GENERAL INFORMATION 19
Document Orientation 19
Safety Considerations 20
Options and Accessories 20
Description 21
Capabilities 21
Front Panel Controls 22
Remote Programming 22
Output Characteristic 22
3 - INSTALLATION 25
Installation and Operating Checklist 25
Inspection 26
Damage 26
Packaging Material 26
Items Supplied 26
Cleaning 26
Location 27
Bench Operatio n 27
Rack Mounting 27
Input Connections 28
Connect the Power Cord 28
Output Connections 28
Current Ratings 28
Voltage Drops and Lead Resistance 28
Remote Sensing 29
Remote Sense Leads 30
Maintaining Stability while Remote Sensing 32
Open Sense Lead Protection 32
Output Compensation (High Mode/Low Mode) 34
Local Sensing 34
OVP Considerations 35
External Protection Connections 36
Digital I/O Connections 37
7
Controller Connections 38
HP-IB Interface 38
RS-232 Interface 38
4 - TURN-ON CHECKOUT 39
Checkout Procedure 39
In Case of Trouble 41
Selftest Error Messages 41
Runtime Error Messages 41
Line Fuse 42
5 - FRONT PANEL OPERATION 43
Introduction 43
Front Panel Description 43
System Keys 45
Function Keys 46
Immediate Action Keys 46
Scrolling Keys 46
Metering Keys 47
Output Control Keys 48
Entry Keys 49
Examples of Front Panel Programming 50
1 - Setting the Output Voltage, Current, and Compensation 50
2 - Querying and Clearing Output Protection and Errors 51
3 – Making Front Panel Measurements 52
4 - Programming External Protection and the Digital Port Functions 54
5 - Setting the HP-IB Address and RS-232 Parameters 54
6 - Saving and Recalling Operating States 55
6 - INTRODUCTION TO PROGRAMMING 57
HP-IB Capabilities of the DC Source 57
HP-IB Address 57
RS-232 Capabilities of the DC Source 57
RS-232 Data Format 57
Baud Rate 57
RS-232 Flow Control 58
Introduction to SCPI 58
SCPI References 58
HP-IB Refe rences 58
Conventions Used in This Guide 59
Types of SCPI Commands 59
Multiple Commands in a Message 60
Moving Among Subsystems 60
Including Common Commands 61
Using Queries 61
Types of SCPI Messages 61
The Message Unit 62
Headers 62
Query Indicator 62
Message Unit Separator 62
Root Specifier 62
Message Terminator 62
SCPI Data Formats 63
Numerical Data Formats 63
8
Suffixes and Multipliers 63
Response Data Types 63
SCPI Command Completion 64
Using Device Clear 64
RS-232 Troubleshooting 65
SCPI Conformance Information 65
SCPI Conf irmed Commands 65
Non-SCPI Commands 65
7 - PROGRAMMING THE DC SOURCE 67
Introduction 67
Programming the Output 67
Power-on Initialization 67
Enabling the Output 67
Output Voltage 68
Output Current 68
Triggering Output Changes 69
SCPI Triggeri ng N omenclature 69
Output Trigger System Model 69
Setting the Voltage or Current Trigger Levels 69
Initiating the Output Trigger System 70
Generating Triggers 70
Making Measurements 71
Controlling Measurement Samples 71
Current Ranges and Measurement Detector (HP Model 66311B Only) 72
Window Functions 72
Voltage and Current Measurements 73
Pulse Measurements (HP Model 66311B Only) 73
Returning All Measurement Data From the Data Buffer 74
Internally Triggered Measurements 75
SCPI Triggeri ng N omenclature 75
Measurement Trigger System Model 75
Initiating the Measurement Trigger System 75
Selecting the Measurement Trigger Source 76
Generating Measurement Triggers 76
Pre-event and Post-event Triggeri ng 78
Programming the Status Registers 79
Power-On Conditions 79
Operation Status Group 81
Questionable Status Group 82
Standard Event Status Group 82
Status Byte Register 82
Determining the Cause of a Service Interrupt 83
Servicing Operation Status and Questionable Status Events 83
Monitoring Both Phases of a Status Transition 84
Inhibit/Fault Indicator 84
Remote Inhibit (RI) 84
Discrete Fault Indicator (DFI) 85
Using the Inhibit/Fault Port as a Digital I/O 85
8 - LANGUAGE DICTIONARY 87
Introduction 87
Subsystem Command s 87
Common Commands 91
9
Programming Parameters 91
Calibration Commands 92
CALibrate:CURRent 92
CALibrate:CURRent:MEASure:LOWRange 92
CALibrate:CURRent:MEASure:AC 92
CALibrate:DATA 93
CALibrate:LEVel 93
CALibrate:PASSword 93
CALibrate:SAVE 93
CALibrate:STATe 94
CALibrate:VOLTage 94
CALibrate:VOLTage:PROTection 94
Display Commands 95
DISPlay 95
DISPlay:MODE 95
DISPlay:TEXT 95
Format Commands 96
FORMat 96
FORMat:BORDer 96
Measurement Commands 97
MEASure:ARRay:CURRent? FETCh:ARRay:CURRent? 97
MEASure:ARRay:VOLTage? FETCh:ARRay:VOLTage? 97
MEASure:CURRent? FETCh:CURRe nt? 98
MEASure:CURRent:ACDC? FETCh:CURRent:ACDC? 98
MEASure:CURRent:HIGH? FETCh:CURRent:HI GH? 98
MEASure:CURRent:LOW? FETCh:CURRent:LOW? 99
MEASure:CURRent:MAXimum? FETCh:CURRent: MAXimum? 99
MEASure:CURRent:MINimum? FETCh:CURRent:MINimum? 99
MEASure:VOLTage? FETCh:VOLTage? 100
MEASure:VOLTage:ACDC? FETCh:VOLTage:ACDC? 100
MEASure:VOLTage:HIGH? FETCh:VOLTage:HIGH? 100
MEASure:VOLTage:LOW? FETCh:VOLTage:LOW? 101
MEASure:VOLTage:MAXimum? FETCh:VOLTage:MAXimum? 101
MEASure:VOLTage:MINimum? FETCh:VOLTage:MINimum? 101
SENSe:CURRent:DETector 102
SENSe:CURRent:RANGe 102
SENSe:FUNCtion 103
SENSe:PROTection:STATe 103
SENSe:SWEep:OFFSet:POINts 103
SENSe:SWEep:POINts 103
SENSe:SWEep:TINTerval 104
SENSe:WINDow 104
Output Commands 105
OUTPut 105
OUTPut:DFI 105
OUTPut:DFI:SOURce 105
OUTPut:PON:STATe 106
OUTPut:PROTection:CLEar 106
OUTPut:PROTection:DELay 106
OUTPut:RI:MODE 107
OUTPut:TYPE 107
[SOURce:]CURRent 108
[SOURce:]CURRent:PROTection:STATe 108
[SOURce:]CURRent:TRIGger 108
[SOURce:]DIGital:DATA 109
10
[SOURce:]DIGital:FUNCtion 109
[SOURce:]VOLTage 109
[SOURce:]VOLTage:PROTection 110
[SOURce:]VOLTage:PROTection:STATe 110
[SOURce:]VOLTage:TRIGger 110
Status Commands 111
STATus:PRESet 111
STATus:OPERation? 111
STATus:OPERation:CONDition? 111
STATus:OPERation:ENABle 112
STATus:OPERation:NTR STATus:OPERation:PTR 112
STATus:QUEStionable? 113
STATus:QUEStionable:CONDition? 113
STATus:QUEStionable:ENABle 113
STATus:QUEStionable:NTR STATus:QUEStionable:PTR 114
System Commands 115
SYSTem:ERRor? 115
SYSTem:LANGuage 115
SYSTem:VERSion? 115
SYSTem:LOCal 116
SYSTem:REMote 116
SYSTem:RWLock 116
Trigger Commands 117
ABORt 117
INITiate:SEQuence INITiate:NAME 117
INITiate:CONTinuous:SEQuence1 INITiate:CONTinuous:NAME TRANsient 117
TRIGger 118
TRIGger:SOURce 118
TRIGger:SEQuence2 TRIGger:ACQuire 118
TRIGger:SEQuence2:COUNt:CURRent TRIGger:ACQuire:COUNt:CURRent 119
TRIGger:SEQuence2:COUNt:VOLTage TRIGger:ACQuire:COUNt:VOLTage 119
TRIGger:SEQuence2:HYSTeresis:CURRent TRIGger:ACQuire:HYSTeresis:CURRent 120
TRIGger:SEQuence2:HYSTeresis:VOLTage TRIGger:ACQuire:HYSTeresis:VOLTage 120
TRIGger:SEQuence2:LEVel:CURRent TRIGger:ACQuire:LEVel:CURRent 121
TRIGger:SEQuence2:LEVel:VOLTage TRIGger:ACQuire:LEVel:VOLTage 121
TRIGger:SEQuence2:SLOPe:CURRent TRIGger:ACQuire:SLOPe:CURRent 122
TRIGger:SEQuence2:SLOPe:VOLTage TRIGger:ACQuire:SLOPe:VOLTage 122
TRIGger:SEQuence2:SOURce TRIGger:ACQuire:SOURce 123
TRIGger:SEQuence1:DEFine TRIGger:SEQuence2:DEFine 123
Common Commands 124
*CLS 124
*ESE 124
*ESR? 125
*IDN? 125
*OPC 125
*OPT? 126
*PSC 126
*RCL 126
*RST 127
*SAV 127
*SRE 128
*STB ? 128
*TRG 129
*TST? 129
*WAI 129
11
Additional Commands 130
INSTrument:STATe 130
OUTPut:PROTection:TRIPped? 130
CURRent:LIMit:HIGH? 130
CURRent:LIMit:LOW? 130
CURRent:PROTection:T RIPped? 131
VOLTage:LIMit:HIGH? 131
VOLTage:LIMit:LOW? 131
VOLTage:PROTection:TRIPped? 131
A - SPECIFICATIONS 133
Specifications 133
Supplemental Characteristics 134
B - VERIFICATION AND CALIBRATION 137
Introduction 137
Equipment Required 137
Test Setup 137
Performing the Verification Tests 138
Turn-On Checkout 138
Check the Language Setting 139
Voltage Programming and Measurement Accuracy 139
Current Programming and Measurement Accuracy 139
Restore the Language Setting 140
Performing the Calibration Procedure 142
Front Panel Calibration Menu 142
Front Panel Calibration Procedure 143
Calibration Error Messages 146
Changing the Calibration Password 146
Calibration Over the HP-IB 146
C - ERROR MESSAGES 147
D - EXAMPLE PROGRAMS 151
E - LINE VOLTAGE CONVERSION 161
F - COMPATIBILITY LANGUAGE 163
INDEX 169
12
Quick Reference
The Front Panel - At a Glance
Quick Reference - 1
1
1 A 14-character display
shows output measurements
and programmed values.
1
66311A 0-15V/0Mobile Communications DC
CV CC
SYSTEM FUNCTION
Error
2
Recall
6
LINE
Local
1
Off
On
2 Annunciators indicate
operating modes and status
conditions.
2
Unr Dis OCP
Input
Address
Meter
3
Protect
78 9
Cal
Shift
Prot
45
Rmt Addr Err SRQ
OV
Voltage
.
Current
0
Output
CalOCPProt CirSave
Output
On/Off
3 Rotary control sets voltage,
current, and menu parameters.
Use and
to set the resolution; then adjust
the value with the knob.
3
ENTRY
Cir Entry
Enter
-
Number
Enter
Backspace
ÊÉ
4 Turns the dc
source on and off.
4
5
5 System keys:
♦ return to Local mode
♦ set the HP-IB
address
♦ set the RS-232
interface
♦ display SCPI error
codes
♦ save and recall
instrument states
♦ select programming
language.
6
6 Function keys:
♦ enable/disable the
output
♦ select metering
functions
♦ program voltage and
current
♦ set and clear protection
functions
♦ and
ô
scroll through the front
panel menu commands.
7
7 Entry keys:
♦ enter values
♦ increment or
decrement values
♦ and
Ì
select front panel
menu parameters.
É Ê
♦ and
select a digit in
the numeric entry
field.
Ë
13
1 - Quick Reference
The Rear Panel - At a Glance
1 AC calibration switch
(see appendix B).
1
WARNING:
WARNING:
2 HP-IB (IEEE-488)
interface connector.
3 RS-232 interface
connector.
2 3 4
NO OPERATOR SERVICEABLE PARTS INSIDE, REFER SERVICING TO SERVICE TRAINED PERSONNEL.
RS 232
LINE
FUSE
AC - I CAL
| Normal
/ Hold to Cal
-S
-+
+S
+
50VDC MAX TO
-
FOR CONTINUED FIRE PROTECTION, USE SPECIFIED LINE FUSE
SENSE
Local
Remote
1A
120V
250V
RATING
000VA
50/60 Hz
FUSE
4 INH/FLT (remote
INHibit / internal
FauLT) connector.
Connector plug is
removable.
INH FLT
+
-+
5 Output and Remote
sense connector.
5 6
6 Remote or Local
sense switch
7 8
7 Fuse holder 8 Power cord connector
(IEC 320)
Connector plug is
removable.
Instrument Configuration
Use the front panel Address key to configure the interface
Refer to “Front Panel Menus - At a Glance”
♦ Select either the HP-IB or RS-232 interface.
♦ Enter the HP-IB bus address.
♦ Configure the RS-232 baud rate, parity, and flow control.
♦ Select either the SCPI or COMPatibility programming language.
♦ Enable the optional HP 14575A remote front panel.
14
Quick Reference - 1
Front Panel Number Entry
Enter numbers from the front panel using one the following methods:
Use the arrow keys and knob to change voltage or current settings
NOTE: The output must be ON to see the displayed values change in Meter mode. With the
output enabled, this method changes the output voltage or current immediately.
Use the Function keys and knob to change the displayed settings
Use the arrow keys to edit individual digits in the displayed setting
Increments the flashing digit
Decrements the flashing digit
Moves the flashing digit to the right
Moves the flashing digit to the left
Enters the value when editing is complete
Use the Function keys and Entry keys to enter a new value
NOTE: If you make a mistake, use the Backspace key to delete the number, or press the Meter
key to return to meter mode.
15
1 - Quick Reference
On/Off
Front Panel Annunciators
CV
CC
Unr
Dis
OCP
Prot
Cal
Shift
Rmt
Addr
Err
The output is operating in constant voltage mode.
The output is operating in constant current mode.
The output is unregulated.
The output is OFF. Press the Output On/Off key to turn the output on.
The over-current protection state is ON. Press the OCP key to turn over-current
protection off.
Indicates that the output has been disabled by one of the protection features.
Press the Prot Clear key to clear the protection condition.
Calibration mode is ON. Scroll to the Cal Off command and press the Enter key
to exit the calibration mode.
The Shift key has been pressed.
The selected Remote programming interface (either HP-IB or RS-232) is active.
Press the Local key to return the unit to front panel control.
The interface is addressed to talk or listen.
There is an error in the SCPI error queue. Press the Error key to view the error
code.
SRQ
The interface is requesting service.
Immediate Action Keys
Output
Local
Shift
Shift
16
Prot Clr
OCP
A toggle switch that turns the output of the dc source on or off.
Activates front panel control when the unit is in remote mode (unless a Lockout
command is in effect).
Resets the protection circuit and allows the unit to return to its last programmed
state.
A toggle switch that enables or disables overcurrent protection.
Front Panel Menus - At a Glance
Quick Reference - 1
Address
ô
ô
ô
ô
ô
ô
Recall
SaveShift
ErrorShift
Meter
ô
ô
ô
ô
ô
ô
ô
ô
ô
ô
Voltage
Current
Protect
Output
ô
ô
ô
ô
ô
ô
ô
ô
ô
OVShift
ô
Shift Input
ô
ô
ô
CalShift
Use and to select parameters (table shows factory defaults). Use to exit any menu.
1
Only available on HP Model 66311B
ADDRESS 7 Sets the HP-IB Address
INTF HPIB Selects an interface (HPIB or RS232)
BAUDRATE 300 Selects baud rate (300, 600, 1200, 2400, 4800, 9600)
PARITY NONE Selects message parity (NONE, EVEN, ODD, MARK, SPACE)
FLOW NONE Selects flow control (XON-XOFF, RTS-CTS, DTR-DSR, NONE)
LANG SCPI Selects language (SCPI or COMP)
REMOTE FP OFF Enables or disables HP 14575A front panel interface (ON or OFF)
*RCL 0 Recalls instrument state
*SAV 0 Saves present instrument state
ERROR 0 Displays errors in SCPI error queue
12.000V 0.204A Measures output voltage and current
12.500V MAX Measures peak output voltage
1.000V MIN Measures minimum output voltage
1
1
12.330V HIGH Measures the high level of a voltage pulse waveform
0.080V LOW Measures the low level of a voltage pulse waveform
12.000V RMS Measures rms voltage
0.350A MAX Measures peak output current
0.050A MIN Measures minimum output current
1
1
1
1
0.400A HIGH Measures the high level of a current pulse waveform
0.012A LOW Measures the low level of a current pulse waveform
0.210A RMS Measures rms current
1
1
VOLT 20.000 Sets the output voltage
CURR 2.000 Sets the output current
OVERCURRENT Protection status (example shows overcurrent tripped)
*RST Places the dc source in the factory-default state
PON:STATE RST Select the power-on state command (RST or RCL0)
PROT:DLY 0.08 Sets the output protection delay in seconds
SENSE:PROT ON Sets the broken sense lead detect circuit on
RI LATCHING Sets the remote inhibit mode (LATCHING, LIVE, or OFF)
DFI OFF Sets the discrete fault indicator state (ON or OFF)
DFI:SOUR OFF Selects the DFI source (QUES, OPER, ESB, RQS, or OFF)
PORT RIDFI Sets the output port functions (RIDFI or DIGIO)
DIGIO 7 Sets and reads the I/O port value (0 through 7)
TYPE:CAP LOW Sets the output capacitance compensation (HIGH or LOW)
VOLT:PROT 22 Sets the overvoltage protection level
PROT:STAT ON Enables or disables overvoltage protection (ON or OFF)
CURR:RANG HIGH Sets the current range (HIGH, LOW, or AUTO)
CURR:DET ACDC
Sets the current measurement detector (ACDC or DC)
1
TINT 46.8 Sets the time interval for a front panel measurement in seconds
POINT 2048 Sets the buffer size for a front panel measurement
CAL ON Accesses calibration menu (See Appendix B).
ËÌ
Meter
1
1
1
17
1 - Quick Reference
SCPI Programming Commands - At a Glance
NOTE: Some [optional] commands have been included for clarity. Refer to chapter 8 for a
complete description of all programming commands.
ABORt SENSe
CALibrate
:CURRent :RANGe <n>
:CURRent [:POSitive] :DETector ACDC | DC
:NEGative :FUNCtion “VOLT” | “CURR”
:MEASure :LOWRange
:AC
1
1
:PROTection :STATe <bool>
:SWEep :OFFSet :POINts <n>
1
1
:DATA <n> :POINts <n>
:LEVel P1 | P2 :TINTerval <n>
:PASSword <n> :WINDow :TYPE “HANN” | “RECT”
:SAVE [SOURce:] CURRent <n>
:STATe <bool> [, <n>] :TRIGgered <n>
:VOLTage [:DC] :PROTection :STATe <bool>
:PROTection DIGital :DATA <n>
DISPlay
:FUNCtion RIDF | DIG
<bool> VOLTage <n>
:MODE NORMal | TEXT :TRIGgered <n>
:TEXT <display_string> :PROTection <n>
FORMat
[:DATA] ASCII | REAL [,length]
STATus
:STATe <bool>
:BORDer NORM | SWAP :PRESet
INITiate
:OPERation [:EVENt]?
:SEQuence[1|2] :CONDition?
:NAME TRANsient | ACQuire :ENABle <n>
:CONTinuous :SEQuence[1], <bool> :NTRansition <n>
:NAME TRANsient, <bool> :PTRansition <n>
MEASure | FETCh
:QUEStionable [:EVENt]?
:ARRay :CURRent? :CONDition?
:VOLTage? :ENABle <n>
[:CURRent] [:DC]? :NTRansition <n>
:ACDC?
:HIGH?
:LOW?
:MAX?
:MIN?
:VOLTage [:DC]? :LOCal
:ACDC?
:HIGH?
:LOW?
:MAX?
:MIN?
OUTPut
1
1
1
1
1
1
1
1
1
1
SYSTem
:ERRor?
:LANGuage SCPI | COMPatibility
:VERSion?
:REMote
:RWLock
TRIGger
:SEQuence2| :ACQuire [:IMMediate]
:PTRansition <n>
:COUNt :CURRent <n>
:VOLTage <n>
<bool> :HYSTeresis:CURRent <n>
:DFI <bool> :VOLTage <n>
:SOURce QUES | OPER | ESB | RQS | OFF :LEVel :CURRent <n>
:PON :STATe RST | RCL0 :VOLTage <n>
:PROTection :CLEar :SLOPe :CURRent POS | NEG | EITH
:DELay <n> :VOLTage POS | NEG | EITH
:RI :MODE LATCHing | LIVE | OFF :SOURce BUS | INTernal
:TYPE [:CAPacitance] HIGH | LOW [:SEQuence1| :TRANsient][:IMMediate]
:SOURce BUS
1
Only available on HP Model 66311B :SEQuence2 :DEFine ACQuire
:SEQuence1 :DEFine TRANsient
18
2
General Information
Document Orientation
This manual describes the operation of the HP Model 66111A Fast Transient and the HP Model 66311B
Mobile Communications DC Source. Unless otherwise noted, these models will be referred to by the
description "dc source" throughout this manual.
The following Getting Started Map will help you find the information you need to complete the specific
task that you want to accomplish. Refer to the table of contents or index of each guide for a complete list of
the information contained within.
Getting Started Map
Task Where to find information
Quick Reference Section
Installing the unit
Line voltage connections
Computer connections
Load connections
Checking out the unit
Verifying proper operation
Using the front panel
Calibrating the unit
Using the front panel
Front panel keys
Front panel examples
Using the programming interface
HP-IB interface
RS-232 interface
Programming the unit using SCPI (and COMPatibility)
commands
SCPI commands
SCPI programming examples
SCPI language dictionary
Programming the unit using the HP VXIplug&play
instrument driver
Installing the instrument driver
Instrument driver functions
C/C++ example programs
Visual BASIC example programs
LabVIEW example programs
HP VEE example programs
Chapter 1
Chapter 2
Chapter 3
Chapter 5
Chapter 6
Chapters 7 and 8 for SCPI commands.
Appendix D for SCPI examples
Appendix F for COMPatibility commands
HP VXIplug&play installation sheet and
on-line help
NOTE:
The driver must be installed on your pc to
access the on-line information.
Drivers for HP-UX are available on the
web at www.hp.com/go/drivers
19
2 - General Informat ion
Safety Considerations
This dc source is a Safety Class 1 instrument, which means it has a protective earth terminal. That
terminal must be connected to earth ground through a power source equipped with a ground receptacle.
Refer to the Safety Summary page at the beginning of this guide for general safety information. Before
installation or operation, check the dc source and review this guide for safety warnings and instructions.
Safety warnings for specific procedures are located at appropriate places in the guide.
Options and Accessories
Table 2-1. Options
Option Description
100
220
230
8ZJ Delete instrument feet option
1
AXS
1
1CM
052 Device characterization software for current measurements and display
1
Support rails are required when rack mounting units. Use E3663A support rails for HP rack cabinets,
and E3664A for non-HP rack cabinets.
87−106 Vac, 47−63 Hz
191−233 Vac, 47−63 Hz
207−253 Vac, 47−63 Hz
Rack mount kit for two side-by-side units of equal depth. Consists of:
Lock-link kit (HP p/n 5061-9694) and Flange kit (HP p/n 5062-3974)
Rack mount kit for one unit (HP p/n 5062-3972)
(available for HP Model 66311B only)
Table 2-2. Accessories
Item HP Part Number
HP-IB cables 1.0 meter (3.3 ft) HP 10833A
2.0 meters (6.6 ft) HP 10833B
4.0 meters (13.2 ft) HP 10833C
0.5 meters (1.6 ft) HP 10833D
RS-232 cable 9-pin F to 9-pin F, 2.5 meter, null modem/printer cable
HP 34398A
with one 9-pin M to 25-pin F adapter
RS-232 adapter kit - contains the following 4 adapters
HP 34399A
9-pin M to 25-pin M for pc or printer
9-pin M to 25-pin M for pc or printer
9-pin M to 25-pin M for modem
9-pin M to 9-pin M for modem
Rack mount with slide - for two side-by-side units of different depths 5062-3996; 1494-0015
Rack mount - for two side by side units of different depths 5062-3996
Rack mount with slide - for one unit 5062-3996; 1494-0015;
5062-4022
Remote Front Panel - for viewing up to six HP 66111A/66311B units that
HP 14575A
are installed in a remote location where the front panels is not visible.
Includes an ac/dc adapter for powering up to 3 remote panels
20
General Information - 2
Description
The HP 66111A is a high performance dc power source that provides peak current sourcing and rapid,
basic measurements in a compact, half-rack box. It is designed to simplify the testing of digital wireless
communications products. Excellent voltage transient response characteristics prevent test interruptions
due to triggering of low voltage phone shutdown. Fast command processing and voltage change response
times maximize throughput. Measurement capability provides rapid dc voltage and current
measurements. The 15 volt source and 5A peak current capability provides compatibility with a number
of communications standards, including: GSM, CDMA, TDMA, PCS, DECT, TERA, PHS, NADC, PHS,
and others.
The HP 66311B is a high performance dc power source that provides all of the capabilities of the HP
66111A plus fast dynamic measurement and analysis of voltage and current waveforms. Dynamic
measurement and analysis of current waveforms combined with precision current measurement let you
characterize cellular phone current requirements under all operating conditions.
Table 2-3. HP 66111A/66311B Differences
Item HP 66111A HP 66311B
Dynamic Measurement capability not available rms, high, low,
max, min
Low range current measurement accuracy not available
+ High range current measurement accuracy 0.2% +9 mA 0.2% +0.5 mA
− High range current measurement accuracy
0.2% +9 mA 0.2% +1.1 mA
0.1% +2.5 µA
Capabilities
♦ Output Voltage and Current control with 12-bit programming resolution.
3 ampere current source capability (up to 5 amperes for 7 milliseconds)
♦ Extensive measurement capability:
dc voltage and current.
rms and peak voltage and current.
Current measurement capability up to approximately 7.0 amperes
16-bit measurement resolution (low range has resolution better than 1 microampere).
Triggered acquisition of digitized current and voltage waveforms (HP 66311B only)
♦ Front panel control with 14-character vacuum fluorescent display, keypad, and rotary control for
voltage and current settings.
♦ Built-in HP-IB and RS-232 interface programming with SCPI command language.
♦ Non-volatile state storage and recall with SCPI command language.
♦ Over-voltage, over-current, over-temperature, and RI/DFI protection features.
♦ Extensive selftest, status reporting, and software calibration.
21
2 - General Informat ion
Front Panel Controls
The front panel has both rotary (RPG) and keypad controls for setting the output voltage and current. The
panel display provides digital readouts of a number of output measurements. Annunciators display the
operating status of the dc source. System keys let you perform system functions such as setting the HP-IB
address and recalling operating states. Front panel Function keys access the dc source function menus.
Front panel Entry keys let you select and enter parameter values. Refer to chapter 5 for a complete
description of the front panel controls.
Remote Programming
NOTE: When shipped, all units are set to the SCPI programming language. The language setting
is saved in non-volatile memory.
To change the programming language from SCPI to COMPatibility language, press the
front panel
COMP, then press
remote programming.
The dc source may be remotely programmed via the HP-IB bus and/or from an RS-232 serial port. HP-IB
programming is with SCPI commands (Standard Commands for Programmable Instruments), which make
the dc source programs compatible with those of other HP-IB instruments. Dc source status registers
allow remote monitoring of a wide variety of dc source operating conditions. A Compatibility language
mode is also included to make the dc source compatible with the HP 6632A, 6633A, and 6634A Series
dc power supplies (refer to appendix E). Note that the compatibility features of this unit are limited to the
features that were originally available on HP 6632A, 6633A, and 6634A units.
Address key, use ô to scroll to the LANG command, press
Enter. Refer to the chapters 6 through 8 for further information about
Ì
to select
Output Characteristic
The dc source’s output characteristic is shown in the following figure. The output of the dc source may be
adjusted to any value within the boundaries shown.
The dc source is capable of providing a constant dc output of 15 volts with up to 3 amperes of current. It
is capable of sourcing peak currents of up to 5 amperes -- provided the peak current pulse does not
exceed 7 milliseconds, and the average current requirement does not exceed 3 amperes. If the unit
attempts to draw current for longer than seven milliseconds, the current limit amplifier will limit the
current to 3.0712 amps. The peak current capability is illustrated by the dotted line in Figure 2-1.
NOTE: To source up to 5 amperes of current for up to 7 milliseconds, the current limit must
be programmed for greater than 3 amperes (up to a maximum of 3.0712 A).
The dc source can operate in either constant voltage (CV) or constant current (CC) over the rated output
voltage and current. Figure 2-1 shows a single range − two quadrant capability. This means that the dc
source is capable of sourcing as well as sinking current over the output voltage range from zero volts to
the rated voltage. This negative current sinking capability provides fast downprogramming of the output
of the dc source. It can also be used to sink current from a battery charger, thus providing battery charger
test capability. The negative current is not programmable, and varies linearly from 1.2 amperes at the full
rated voltage, to 2.8 amperes at zero output voltage.
22
General Information - 2
Figure 2-1. Dc Source Output Characteristic
The operating point of the unit is determined by the voltage setting, current setting, and the load
Output
Voltage
ISET
15V
-1.2A
1
VSET
ne
i
l
oad
l
e
v
-2.8A
i
t
s
i
es
r
V
C
s
e
r
C
C
0
a
o
l
e
v
i
t
s
i
2
e
n
i
l
d
Peak Current
capability for up
to 7 ms shown
by dotted lines
3A
5A
+-
Output
Current
resistance. In figure 2-1, operating point 1 is defined by the load line traversing the positive operating
quadrant in the constant voltage region. Operating point 2 is defined by the load line traversing the
positive operating quadrant in the constant current region.
NOTE: If you attempt to operate the dc source beyond its output ratings, the output of the unit
may become unregulated. This is indicated by the UNR annunciator on the front panel.
The output may also become unregulated if the ac line voltage drops below the minimum
rating specified in Appendix A.
Appendix A documents the dc source’s specifications and supplemental characteristics.
23
3
Installation
Installation and Operating Checklist
Check the Output Compensation
¨ Check that the output compensation of the dc source is appropriate for your application. Refer to
“Output Compensation” in this chapter.
High mode provides the best transient response and can be used with phones having input capacitances
from 5 to 12000 µF. Note that if the last two digits on the front panel display are fluctuating when the
phone is in standby, you may want to set the output compensation to Low mode.
Low mode is used when testing phones having input capacitances from 0 to 12000 µF. Standard dc
sources are factory-set to Low mode.
Check the Sense and Load Connections
¨ If you are remote sensing, is the sense switch on the back of the dc source in the Remote position?
Remote sensing is recommended for most applications. Push the switch out for remote sensing. Attempting
to operate the unit with the switch in the out position without connecting the sense leads may result in an
overvoltage or remote sense detect shutdown. Refer to “Remote Sensing” in this chapter.
¨ If you are remote sensing, are the + and − sense leads connected ONLY at the test fixture and
within 20 inches of the phone contacts? For best performance, the distance from sense lead termination to
the phone contacts should be as short as possible. Refer to “Lead Resistance” in this chapter.
Check the Operating Settings and Conditions
¨ Are you able to communicate remotely with the dc source? If not, check that the address setting and
the programming language are set correctly. Refer to “HP-IB address” and “Language setting” in chapter
5.
¨ Is the Prot or Err annunciator on the front panel on? If yes, clear the fault condition before
continuing. Refer to “Clearing Protection” in chapter 5.
¨ Is the Overvoltage circuit shutting the unit down? If yes, you can disable the overvoltage circuit.
Refer to “Clearing Protection” in chapter 5.
¨ Are the front panel readings unstable? If yes, check that the front panel sampling rate is correct. Also
check the setting of the output compensation. Refer to “Front Panel Measurements” in chapter 5 and
“Output Compensation” in this chapter.
Additional HP 66311B Operating Settings Checks
¨ Are you measuring dynamic output currents? If yes, check that the current detector is set to ACDC.
Refer to “Front Panel Measurements” in chapter 5.
¨ Are you measuring output currents under 20 mA? If yes, check that the current range is set to LOW.
Refer to “Front Panel Measurements” in chapter 5.
25
3 - Installation
Inspection
Damage
When you receive your dc source, inspect it for any obvious damage that may have occurred during
shipment. If there is damage, notify the shipping carrier and the nearest HP Sales and Support Office
immediately. The list of HP Sales and Support Offices is at the back of this guide. Warranty information
is printed in the front of this guide.
Packaging Material
Until you have checked out the dc source, save the shipping carton and packing materials in case the unit
has to be returned. If you return the dc source for service, attach a tag identifying the model number and the
owner. Also include a brief description of the problem.
Items Supplied
The following user-replaceable items are included with your dc source. Some of these items are installed in
the unit.
Table 3-1. Items Supplied
Item Part Number Description
Power Cord contact the nearest HP
Sales and Support Office
Digital connector 1252-1488 4-terminal digital plug that connects to the back of the
Output connector 0360-2604 5-terminal plug that connects to the back of the unit.
Line Fuse 2110-0303
2110-0007
Feet 5041-8801 feet for bench mounting
User's Guide 5964-8106 Contains installation, checkout, and front panel
A power cord appropriate for your location.
unit.
2 A slow-blow for 100/120 Vac operation
1 A slow-blow for 220/230 Vac operation
programming information.
Cleaning
Use a dry cloth or one slightly dampened with water to clean the external case parts. Do not attempt to
clean internally.
WARNING: To prevent electric shock, unplug the unit before cleaning.
26
Installation - 3
Location
The outline diagram in figure 3-1 gives the dimensions of your dc source. The dc source must be installed
in a location that allows sufficient space at the sides and back of the unit for adequate air circulation (see
Bench Operation).
Bench Operation
Do not block the fan exhaust at the rear of the unit.
A fan cools the dc source by drawing air in through the sides and exhausting it out the back. Minimum
clearances for bench operation are 1 inch (25 mm) along the sides.
Rack Mounting
The dc source can be mounted in a standard 19-inch rack panel or cabinet. Table 2-1 documents the HP
part numbers for the various rack mounting options that are available for the dc source. Installation
instructions are included with each rack mount option.
NOTE: Support rails or an instrument shelf is required when rack mounting units.
Figure 3-1. Outline Diagram
27
3 - Installation
Input Connections
Connect the Power Cord
1. Unscrew the line fuse cap from the rear panel and verify that the fuse rating matches what is
specified on the FUSES label on the rear panel. Reinstall the fuse. (See table 3-1 for fuse part
numbers.)
2. Connect the power cord to the IEC 320 connector on the rear of the unit. If the wrong power cord
was shipped with your unit, contact your nearest HP Sales and Support Office to obtain the correct
cord (refer to the list at the back of this guide).
Output Connections
Turn the unit off before connecting any wires.
The output connector has a termination for the + and − output, the + and − sense terminals, and an earth
ground terminal. The 5-pin connector is removable and accepts wires sizes from AWG 22 to AWG 12.
Disconnect the mating plug from the unit by pulling it straight back.
Current Ratings
Fire Hazard To satisfy safety requirements, load wires must be large enough not to overheat when
carrying the maximum short-circuit current of the dc source.
The following table lists the characteristics of AWG (American Wire Gage) copper wire.
Table 3-2. Ampacity and Resistance of Stranded Copper Conductors
AWG No. Maximum Ampacity (in
free air)
24 3.52 0.0843 0.0257
22 5.0 0.0531 0.0162
20 8.33 0.0331 0.0101
18 15.4 0.0210 0.00639
16 19.4 0.0132 0.00402
14 31.2 0.0083 0.00252
12 40 0.0052 0.00159
Resistance (at 20 deg. C)
Ω/m Ω/ft
Voltage Drops and Lead Resistance
To optimize the performance and transient response in your test system, please observe the following
guidelines:
♦ Twist the load leads together and keep them short. The shorter the leads, the better the performance.
♦ When remote sensing, twist the sense leads together but do not bundle them in with the load leads.
♦ Keep the total cable length to 18 inches or less when local sensing.
♦ Keep the total cable length to the load to 20 ft or less when remote sensing. (Note that the unit has
been tested with cable lengths of up to 40 feet.)
28
Installation - 3
The load wires must also be of a diameter large enough to avoid excessive voltage drops due to the
impedance of the wires. In general, if the wires are heavy enough to carry the maximum short circuit
current without overheating, excessive voltage drops will not be a problem.
The maximum allowable value of load lead resistance is 4 ohms total (2 ohms per side). This may be
further limited to a lower value, based on peak current loading, by the maximum allowable dc voltage
drop of 8 volts total (4 volts per side) as specified for remote sense operation. To illustrate, for up to 2
amps peak, the maximum allowable resistance is 4 ohms total, resulting in a maximum voltage drop of up
to 8 volts. For 4 amps peak the maximum allowable resistance is 2 ohms total, again resulting in a
maximum allowable voltage drop of up to 8 volts.
In addition to keeping dc resistance low, you also need to minimize the total impedance. For higher slew
rate currents (0.2 to 0.3 amps/µs) and long wiring lengths (10 to 20 ft.) the inductance can have as much
effect as the resistance. To minimize inductance, twist the load leads. The inductance will be on the order
of 0.15 µH/ft if twisted, and 0.4 µH/ft if untwisted. In addition to lowering the inductance, twisting the
leads will reduce noise pick up. If you are using remote sense leads, connect these as a second twisted
pair. Do not twist or bundle them with the load leads.
NOTE: The use of relays between the dc source and the phone also increases impedance. Low
resistance relays will improve system performance.
Remote Sensing
Turn the unit off before connecting any wires.
With the Remote/Local switch in the Remote position, the dc source regulates the output voltage at
the output terminals on the back of the unit. External sense terminals are available on the back of the unit
that allow the output voltages to be sensed at the load, compensating for impedance losses in the load
wiring. Remote sensing is illustrated in figure 3-2.
NOTE: For the majority of phone applications, remote sensing is highly recommended. In many
cases, remote sensing must be used to ensure stability and optimize transient response.
The output connector accepts wires sizes from AWG 22 to AWG 12. Disconnect the mating plug to m ake
your wiring connections. When the sense wire connections are complete, set the R emote/Local switch on
the back of the unit to Remote (switch is out).
29
3 - Installation
HP 66311A OUTPUT
CONNECTOR
-S - + +S
TWIST PAIR
SENSE
Local
Remote
TWIST LEADS
Figure 3-2. Remote Sense Connections
SENSE
SWITCH OUT
+
_
WIRE RESISTANCE
LOAD
Remote Sense Leads
Testing has verified stable performance with the sense leads connected up to 20 inches from the phone.
However, for optimum performance, connect the sense leads as close as possible to the phone under test.
To minimize inductance, connect the sense leads as a separate twisted pair.
The sense leads are part of the dc source’s feedback path and must be kept at a low resistance (less than
several ohms) to maintain optimal performance. Connect the sense leads carefully so that they do not
become open-circuited. If the sense leads are left unconnected or become open during operation, the dc
source will not regulate the output voltage. See "Open Sense Lead Protection".
Connect the remote sense leads only to the remote sense connections at the output connector and at the
location on the test fixture where you want to sense the output voltage. There must be not be any
continuity from the sense leads to earth ground or from the sense leads to the output leads other than at
the test fixture. The open sense detect circuit will check for continuity in the sense leads when the output
is turned.
Figure 3-3 shows how to connect remote sense leads and load leads when external disconnect relays are
included in the load path.
NOTE: In this arrangement, the output of the unit should be programmed OFF before the relays
are switched. This is because if the load leads are opened before the sense leads, the
overvoltage protection circuit will trip if it is enabled.
30
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