Agilent Technologies 6811B User manual

User’s Guide
AC Power Solutions
Agilent Models 6811B, 6812B, and 6813B
For instruments with Serial Numbers:
Agilent 6811B: US38390101-up
Agilent 6812B: US38390101-up
Agilent 6813B: US38390101-up
Agilent Part No. 5962-0829 Printed in U.S.A.
Microfiche No 5962-0830 December, 1998
Update April 2000

2
Warranty Information
CERTIFICATION
Agilent Technologies certifies that this product met its published specifications at time of shipment from the factory.
Agilent Technologies 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.
WARRANTY
This Agilent Technologies hardware product is warranted against defects in material and workmanship for a period
of three years from date of delivery. Agilent Technologies software and firmware products, which are designated by
Agilent Technologies 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 Agilent Technologies will, at its option, either
repair or replace products which prove to be defective. Agilent Technologies 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 Agilent Technologies. Customer shall prepay shipping charges by (and shall pay all duty and taxes)
for products returned to Agilent Technologies for warranty service. Except for products returned to Customer from
another country, Agilent Technologies shall pay for return of products to Customer.
Warranty services outside the country of initial purchase are included in Agilent Technologies product price, only if
Customer pays Agilent Technologies international prices (defined as destination local currency price, or U.S. or
Geneva Export price).
If Agilent Technologies 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 Agilent Technologies.
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. AGILENT TECHNOLOGIES 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. AGILENT
TECHNOLOGIES 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
Agilent Technologies Sales and Service office for further information on Agilent Technologies’ full line of Support
Programs.

3
Safety Summary
The
f
ollowin
g
g
eneral sa
f
et
y
p
recautions must be observed durin
g
all
p
hases o
f
o
p
eration o
f
this instrument.
Failure to com
p
l
y
with these
p
recautions or with s
p
eci
f
ic warnin
g
s elsewhere in this manual violates sa
f
et
y
standards o
f
desi
g
n, manu
f
acture, and intended use o
f
the instrument. A
g
ilent Technolo
g
ies assumes no liabilit
y
f
or the customer’s
f
ailure to com
p
l
y
with these re
q
uirements.
WARNING: LETHAL VOLTAGES
Ac sources can supply 425 V peak at their output. DEATH on contact may result if the output terminals or circuits
connected to the output are touched when power is applied.
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 CONDITONS
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 a
pp
ear dama
g
ed or de
f
ective should be made ino
p
erative and secured a
g
ainst unintended
o
p
eration until the
y
can be re
p
aired b
y
q
uali
f
ied service
p
ersonnel.

4
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
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)
WARNING The WARNING si
g
n denotes a hazard. It calls attention to a
p
rocedure,
p
ractice, or the like,
which, if not correctl
y
p
erformed or adhered to, could result in
p
ersonal in
j
ur
y
. Do not
p
roceed
be
y
ond a WARNING si
g
n until the indicated conditions are full
y
understood and met.
Caution The CAUTION si
g
n denotes a hazard. It calls attention to an o
p
eratin
g
p
rocedure, or the like,
which, if not correctl
y
p
erformed or adhered to, could result in dama
g
e to or destruction of
p
art
or all of the
p
roduct. Do not
p
roceed be
y
ond a CAUTION si
g
n until the indicated conditions
are full
y
understood and met.

5
Declaration Page
DECLARATION OF CONFORMITY
according to ISO/IEC Guide 22 and EN 45014
Manufacturer’s Name: Agilent Technologies, Inc.
Manufacturer’s Address: 140 Green Pond Road
Rockaway, New Jersey 07866
U.S.A.
declares that the Product
Product Name: a) AC Power Source/Analyzer
b) Harmonic/Flicker Test System
Model Number(s): a) Agilent 6811B, 6813B, 6812B, 6811A, 6812A, 6813A
b) Agilent 6841A, 6842A
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 A
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 January 1997 __ __
Location Date Bruce Krueger / Quality Manager
European Contact: Your local Agilent Technologies Sales and Service Office or Agilent Technologies GmbH,
Department TRE, Herrenberger Strasse 130, D-71034 Boeblingen (FAX:[phone])

6
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 Agilent Technologies. The information contained in this document is subject to change
without notice.
Copyright 1995, 1997, 1998 Agilent Technologies, Inc. Edition 1 _________August, 1995
Edition 2 _________February, 1997
Edition 3 _________March, 1998
Edition 4 _________December 1998
Update _________April 2000

7
Table of Contents
Warranty Information 2
Safety Summary 3
Declaration of Conformity 5
Acoustic Noise Information 6
Printing History 6
Table of Contents 7
1 GENERAL INFORMATION 11
Document Orientation 11
Earlier AC Source Models 12
Safety Considerations 12
Options and Parts 12
Description 13
Capabilities 14
Front Panel/Remote Operation 14
Steady-state Output Characteristic 15
Peak Current/Dynamic Power Capability 16
Peak Current Limit 16
Peak Inrush Example 16
RMS Current Limit Circuit 17
Voltage Regulation 18
Real Time Regulation 18
RMS Regulation 18
Output Impedance 18
Output Coupling 19
2 INSTALLATION 21
Inspection 21
Damage 21
Packaging Material 21
Items Supplied 21
Cleaning 21
Location 22
Bench Operation 22
Rack Mounting 22
Input Connections 23
Input Source and Line Fuse 23
Installing the Power Cord 23
Output Connections 24
Wire Considerations 25
Voltage Drops 25
Remote Sense Connections 25
Remote Sensing and OVP Considerations 27
Trigger Connections 27
Digital Connections 27
Controller Connections 28
GPIB Connector 28
RS-232 Interface 28

8
3 TURN-ON CHECKOUT 31
Introduction 31
Preliminary Checkout 31
Using the Keypad 32
Checkout Procedure 32
In Case of Trouble 34
Error Messages 34
Line Fuse 35
4 FRONT PANEL OPERATION 37
Introduction 37
Front Panel Description 37
System Keys 39
Function Keys 40
Immediate Action Keys 40
Scrolling Keys 40
Meter Display Keys 41
Output Control Keys 42
Protection and Status Control Keys 44
Trigger and List Control Keys 45
Entry Keys 46
Examples of Front Panel Programming 47
1 - Setting the Output Voltage Amplitude 47
2 - Setting the Output Frequency 47
3 - Setting the DC Offset 48
4 - Setting a Protection Feature 48
5 - Clearing Protection Conditions 49
6 - Using Transient Voltage Modes 50
7 - Trigger Delays and Phase Synchronization 53
8 - Using Slew Rates to Generate Waveforms 55
9 - Measuring Peak Inrush Current 57
10 - Setting the GPIB Address and RS-232 Parameters 58
11 - Saving and Recalling Operating States 58
A SPECIFICATIONS 59
Specifications 59
Supplemental Characteristics 61
Operation Below 45 Hz 53
B VERIFICATION AND CALIBRATION 65
Introduction 65
Equipment Required 65
Test Setup 66
Performing the Verification Tests 67
Turn-On Checkout Procedure 67
AC Voltage Programming and Measurement Accuracy 67
DC Voltage Programming and Measurement Accuracy 68
RMS Current Accuracy Test 68
Performing the Calibration Procedure 71
Front Panel Calibration Menu 71
Front Panel Calibration 72

9
Enable Calibration Mode 72
Calibrating and Entering Voltage Offset Values 72
Calibrating and Entering DC Voltage Gain Values 73
Calibrating and Entering AC rms Voltage Gain Values 73
Calibrating the OVP Trip Point 74
Calibrating and Entering rms Current Values 74
Calibrating and Entering rms Current Measurement Values 75
Calibrating the Output Impedance 75
Saving the Calibration Constants 75
Changing the Calibration Password 76
Calibration Error Messages 76
Calibration Over the GPIB 76
Agilent Calibration Program Listing 76
C ERROR MESSAGES 81
Error Number List 81
D LINE VOLTAGE CONVERSION 85
Open the Unit 85
Check the Jumper Wire (Model Agilent 6811B/6812B only) 85
Check the Line Jumpers (all Models) 85
Check the Power Transformer Connector (all Models) 85
Close the Unit 86
INDEX 87

11
1
General Information
Document Orientation
This manual describes the operation of the Agilent 6811B/6812B/6813B AC Power Solutions. These units
will be referred to as "ac sources" throughout this manual. The following documents are shipped with
your ac source:
♦a Quick-Start Guide, to help you quickly get started using the ac source
♦a User’s Guide, containing detailed installation, checkout, and front panel information
♦a Programming Guide, containing detailed GPIB programming information
♦a Quick Reference Card, designed as a memory jogger for the experienced user
You will find information on the following tasks in these guides. Refer to the table of contents of each
guide for a complete list of the topics.
Topic Location
Accessories and Options Chapter 1 - this guide
Calibrating the ac source Appendix B - this guide
Front panel keys Chapter 4 - this guide
Front panel programming examples Chapter 4 - this guide
Line voltage connections Chapter 2 - this guide
Line voltage ratings Appendix A - this guide
Line voltage conversion Appendix D - this guide
Operator replaceable parts Chapter 1 - this guide
Operator troubleshooting Chapter 3 - this guide
Operating characteristics Appendix A - this guide
Performance specifications Appendix A - this guide
Quick operating checkout Chapter 3 - this guide
Rack mounting Chapter 2 - this guide
RS-232 operation Chapter 2 - this guide
SCPI programming examples Chapter 3 - Programming Guide
SCPI programming commands Chapter 4 - Programming Guide
Turn-on/checkout Chapter 3 - this guide
Wiring - discrete fault indicator (DFI) Chapter 2 - this guide
- GPIB controller Chapter 2 - this guide
- load or loads Chapter 2 - this guide
- voltage sensing (local and remote) Chapter 2 - this guide
- remote inhibit (RI) Chapter 2 - this guide

1 - General Information
12
Earlier AC Source Models
With the exception of some minor readback specification differences, information in this manual also
applies to the following earlier ac source models:
Information about this
current model also applies to the following earlier models:
Agilent 6811B Agilent 6811A AC Power Source/Analyzer
Agilent 6812B Agilent 6812A AC Power Source/Analyzer
Agilent 6841A Harmonic/Flicker Test System
in normal mode
Agilent 6813B Agilent 6813A AC Power Source/Analyzer
Agilent 6842A Harmonic/Flicker Test System
in normal mode
Safety Considerations
This ac 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 ac 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 Parts
Table 1-1. Options
Option Model Description
0BN All Extra documentation
1CM All Rack mount kit (Agilent p/n 5062-3977)
1CP All Rack mount kit with handles (Agilent p/n 5062-3983)
100 Agilent 6811B/6812B 87-106 Vac, 48-63 Hz (Japan only)
200 Agilent 6813B 174-106 Vac, 48-63 Hz (Japan only)
230 Agilent 6811B/6812B 191-254 Vac, 48-63 Hz
831 Agilent 6812B/6813B 12 AWG, 200 to 240 Vac, unterminated
832 Agilent 6813B 4-mm2 wire size, unterminated
833 Agilent 6812B 1.5-mm2 wire size, 200 to 240 Vac, unterminated
834 Agilent 6812B 10 AWG, 100 to 120 Vac, unterminated
841 Agilent 6812B/6813B Line cord with NEMA 6-20P; 20A, 250 V plug
842 Agilent 6813B Line cord with IEC 309; 32A, 220 V plug
844 Agilent 6813B Line cord with NEMA 6-30P; 30A, 250 V locking plug
845 Agilent 6812B Line cord with IEC 309; 16 A, 220 V plug
846 Agilent 6812B Line cord with NEMA L5-30P; 30 A, 120 V plug
847 Agilent 6812B Line cord with CEE 7/7; 16 A, 220 V plug
848 Agilent 6812B Line cord with BS 546; 15 A, 240 V plug
Support rails (Agilent p/n 1494-0059) are required when rack mounting units with options 1CM and 1CP.
Agilent 6811B units are shipped with the correct line cord for the destination country.

General Information - 1
13
The following table lists some common user-replaceable parts:
Table 1-2. Operator Replaceable Parts
Item Agilent Part Number
Power cord assembly see "Options"
Rack mount kit see "Options"
4-terminal digital connector plug 1252-1488
Ac input safety cover (with strain relief and bushing) 5040-1676
Screw (3), ac input barrier block (6-32 x 5/16in) N/A
Ac output safety cover 5040-1704
Line fuse for Agilent 6812B (30 AM) 2110-0910
Line fuse for Agilent 6813B (25 AM) 2110-0849
Line fuse for Agilent 6811B (20 AM) 2110-0098
Screw (2), ac output safety cover (m4 x 0.7in) 0515-0053
Screw (5), ac output barrier block (6-32 x 5/16 in) N/A
User’s Guide (this manual) 5962-0829
Programming Guide 5962-0889
Quick Start Guide 5962-0883
Quick Reference Card 5962-0885
Description
The ac source combines three instruments in one unit as shown in the following figure. The function
generator produces waveforms with programmable amplitude, frequency, and shape. The power
amplifier amplifies the function generator signal to produce the ac power for your application. The
measurement functions range from a simple readback of rms voltage and current, to sophisticated
capabilities such as waveform analysis.
Figure 1-1. AC Source Functional Elements
SOURCE
DAC
MEASUREMENT
shunt
POWERMETER
BIPOLAR
AMPLIFIER
WAVEFORM
GENERATOR BLOCK
FFT ANALYZER

1 - General Information
14
The following model ac power sources are described in this User’s Guide:
Model Description
Agilent 6811B 0-300 V rms; 375 VA (425 V peak; 40 A peak)
Agilent 6812B 0-300 V rms; 750 VA (425 V peak; 40 A peak)
Agilent 6813B 0-300 V rms; 1750 VA (425 V peak; 80 A peak)
Capabilities
♦Programmable ac voltage, dc voltage, frequency, phase, and current limit.
♦Sine, square, clipped sine, and user-definable waveforms.
♦Programmable output impedance.
♦Voltage and frequency slew control.
♦Synthesized waveform generation for high resolution and accuracy in frequency, low waveform
distortion, and glitch-free phase transitions.
♦Step and pulse output transients for generating surge, sag, dropout, and other line disturbance
simulations.
♦Nonvolatile list programming for generating complex output transients or test sequences.
♦Nonvolatile state and waveform storage and recall.
♦Extensive measurement capability:
Ac rms, dc, ac+dc voltage and current and peak current.
Real, reactive, and apparent power.
Harmonic analysis of voltage and current waveforms gives amplitude, phase, and total
harmonic distortion results up to the 50th harmonic.
Triggered acquisition of digitized voltage and current with extensive post-acquisition
calculations.
All measurements made with 16-bit resolution.
♦Trigger In and Trigger Out for synchronizing transient events or measurements with external
signals.
♦Front panel control with 14-character vacuum flourescent display, keypad, and rotary pulse
generators for voltage and frequency settings.
♦Built-in GPIB and RS-232 interface programming with SCPI command language.
♦Over-voltage, over-power, over-current, over-temperature, and RI/DFI protection features.
♦Built-in output and sense disconnect relays.
♦Output terminals floating with respect to chassis ground.
♦Extensive selftest, status reporting, and software calibration.
Front Panel/Remote Operation
The front panel has both rotary (RPG) and keypad controls for setting the output voltage and frequency.
The panel display provides digital readouts of a number of output measurements. Annunciators display
the operating status of the ac source. System keys let you perform system functions such as setting the
GPIB address and recalling operating states. Front panel Function keys access the ac source function
menus. Front panel Entry keys let you select and enter parameter values. Refer to Chapter 4 for a
complete description of the front panel controls.

General Information - 1
15
Remotely programming is accomplished from either the GPIB bus or from an RS-232 serial port. GPIB
and RS-232 programming uses SCPI commands (Standard Commands for Programmable Instruments)
that make the ac source programs compatible with those of other instruments. AC source status registers
permit remote monitoring of a wide variety of ac source operating conditions
NOTE: Refer to the ac source Programming Guide for further information about remotely
programming the ac source.
Steady-state Output Characteristic
The ac source’s steady-state output characteristic is shown in the following figure. Steady-state
characteristics are defined as those output ratings that will be maintained by the ac source for an
indefinite time. (The section "Peak Current Capability" describes the dynamic output capability of the
unit.) The figure shows both the ac and the dc characteristics. With programmable output coupling, the ac
source can supply dc as well as ac output voltages.
Ac source operation is specified from 45 to 1000 Hz (see Appendix A). However, you can operate the
unit at frequencies less that 45 Hz. The operating characteristics of the ac source at autput frequencies
below 45 Hz are documented in Table A-3 of Appendix A.
Figure 1-2. Steady-state Output Characteristic (in real-time mode)
Vrms
Irms
300 V
2.5A (6812B)
5.8A (6813B)
0
115V (6811B/6812B)
135V (6813B)
6.5A (6812B)
13A (6813B)
AC CHARACTERISTIC
Vdc
Idc
424 V
1.35A (6812B)
3.17A (6813B)
0
115V (6811B/6812B)
135V (6813B)
5A (6812B)
10A (6813B)
DC CHARACTERISTIC
-Idc
-Vdc
750VA (6812B)
1750VA (6813B)
575W (6812B)
1350W (6813B)
-424 V
-5A (6812B)
-10A (6813B)
375VA (6811B)
1.25A (6811B) 3.25A (6811B)
285W (6811B)
0.67A (6811B) 2.5A (6811B)
-2.5A (6811B)
(45Hz - 1kHz sinewave)

1 - General Information
16
Peak Current/Dynamic Power Capability
The ac source can generate peak currents that exceed the rms current capability of the unit. This not only
applies when operating in ac mode, but also when programming output pulses in dc mode. Although the
unit will generate peak output currents up to 40A (Agilent 6811B/6812B) or 80A (Agilent 6813B), the unit
can only maintain this output for a limited time. If the output of the unit exceeds the limit of the safe
operating area (SOA), the unit will activate its internal protection mode and turn its output off. This SOA
limit is based on output voltage, output current, output duration, and heatsink temperature.
NOTE: Refer to Chapter 4 on how to clear the unit when the internal protection mode has been
activated.
Peak Current Limit
By programming the peak current limit, you can prevent the unit from exceeding the safe operating area,
activating its internal protection mode, and turning the output off. The peak current limit circuit limits the
instantaneous output current. It functions by reducing the instantaneous output voltage to keep the output
peak current within the programmed limit. Because the circuit acts instantly, the effect is that it will clip
the peaks of the output voltage waveform. Additionally, with fast and/or large voltage transitions, the
unit may momentarily go into CC operating mode due to current in the output capacitor. This serves to
limit the rate of change of output voltage.
The following table gives approximate indications of how long the unit will tolerate peak output currents
before the SOA limits are exceeded. Because these values are voltage dependent, the table includes
various equivalent dc voltages along with the peak current values. The voltages shown in the table are
NOT the programmed voltages, but the average voltage values that will appear at the output when the
indicated high current condition exists. The SOA circuit becomes active at higher voltage and current
values as well as at longer duration times.
Table 1-3. Typical Peak Current Output Capacities
Agilent Agilent 6811B equivalent dc voltage when current is flowing1
6813B Agilent 6812B 25 75 125 190 250 360
20 A 10 A >100 ms >100 ms >100 ms >100 ms >100 ms >100 ms
30 A 15 A >100 ms 100 ms 30 ms 24 ms 19 ms 15 ms
40 A 20 A 12 ms 9.2 ms 8.4 ms 7.6 ms 6.8 ms 5.9 ms
50 A 25 A 5.6 ms 5.1 ms 4.7 ms 4.4 ms 4 ms 3.5 ms
60 A 30 A 3.7 ms 3.4 ms 3.1 ms 2.9 ms 2.6 ms 2.3 ms
70 A 35 A 2.6 ms 2.4 ms 2.2 ms 2.1 ms 1.9 ms 1.7 ms
80 A 40 A 2 ms 1.8 ms 1.7 ms 1.6 ms 1.4 ms 1.3 ms
1Based on 25C ambient temperature, with heatsink temperature less than 50C.
Peak Inrush Example
The following table gives the recommended initial Ipeak settings when the ac source output is a 127 Vac or
254 Vac 60 Hz sine wave, as a function of load capacitance. The load on the output is a full-wave bridge
along with the indicated capacitor. The load resistance across the capacitor is infinite. The recommended
Ipeak will change as a function of changes in input as follows:

General Information - 1
17
♦as voltage increases, the Ipeak setting needs to be decreased.
♦as frequency increases, the Ipeak setting can be increased.
♦as load resistance decreases, the Ipeak setting needs to be decreased.
Note that the purpose of programming the Ipeak current is to prevent the unit from activating its internal
protection mode as a result of exceeding the SOA limits, and turning the output off. These initial settings
may have to be reduced if the SOA circuit trips when the output is turned on. Sometimes trial and error
must be used to arrive at the proper values of Ipeak.
Table 1-4. Recommended Ipeak Settings as a Function of Loop Capacitance
Capacitance in µFI
p
eak setting
127 V 254 V
≤1100 500 80 A
1200 - 60 A
1700 700 50 A
5000 1000 45 A
> 5000 > 1000 < 45 A
The following waveform illustrates the inrush current capability of the ac source. The peak current is
limited during inrush in accord with table 1-3 to keep the ac source from turning its output off. Note that
the output current waveform returns to its normal shape when the current drops below the peak current
limit setting.
Figure 1-3. Peak Inrush Current Example
0
I PEAK=45A
CURRENT
WAVEFORM VOLTAGE
WAVEFORM
VOLTAGE IS
UNDISTORTED
PEAK CURRENT
< 45 A
(115 Vrms)

1 - General Information
18
RMS Current Limit Circuit
The output rms current limit is adjustable to any value within the range of the unit. If the load attempts
to draw more current than the programmed limit, the output voltage is reduced to keep the rms current
within the limit. When the output voltage is reduced, the waveform shape is preserved. In other words, all
parts of the voltage cycle are reduced -- not just the peaks.
NOTE: The speed at which the rms current circuit operates depends on the output voltage setting
and the load impedance. The circuit responds more slowly at low output voltages and at
high output impedances. With constant power or negative resistance loads, the rms
current limit circuit causes the output voltage to go to zero.
Voltage Regulation
Real Time Regulation
The default method of output regulation used by the ac source is real-time voltage regulation. Real-time
voltage regulation tries to provide the actual programmed waveform at the output of the ac source. It
offers the best overall programming response and fastest settling times. It does not have any limitations
for waveforms and transients with frequency content below 45 Hz.
RMS Regulation
Rms voltage regulation assists real-time regulation to level out or stabilize the rms value of the ac
component of the output voltage. Use rms voltage regulation in the following situations:
♦If you experience load regulation effects with heavy loads.
♦If you experience frequency regulation problems with heavy loads and you require flatter
programming accuracy at higher frequencies.
♦In conjunction with programmable output impedance, if you wish to maintain the rms level of
output voltage as the source impedance is increases. (Refer to Output Impedance for more
information.)
The command to specify voltage regulation is VOLT:ALC:DET RTIM | RMS.
NOTE: Do not use rms voltage regulation when operating at frequencies less than 45 Hz.
Output Impedance
You can program the real and/or reactive (resistive and/or inductive) part of the output impedance of the
ac source. Inductive output impedances can be programmed in the range of 20 to 1000 microhenries.
Resistive load impedances can be programmed in the range of 0 to 1 ohms.
When programming output impedances, the lower your load impedance, the LESS programmed
impedance you can use and still maintain output voltage stability. This applies particularly for load
impedances less than 1 ohm.

General Information - 1
19
CAUTION: Programming the ac source output impedance into a load with a low impedance can
cause output voltage instability, which may damage the ac source. Stability MUST
be maintained when operating the ac source with programmable resistance or
inductance.
To check for stability, monitor the output voltage with an oscilloscope. Instability exists
if a 5kHz to 20kHz oscillation, which is dependent upon the ac source’s programmed
inductance and the capacitance of the load, is present at any time during the following
procedure.
1. When programming inductance, it is recommended that you first add a series
resistance either by programming the output resistance to 1 ohm or by adding an
equivalent external resistor.
2. Slowly program the inductance to the desired level while monitoring the output for
any voltage instability. Do not proceed any further if the output shows any signs of
instability.
3. If less output resistance is required, slowly start lowering the resistance while
monitoring the output for any voltage instability. Do not proceed any further if the
output shows any signs of instability.
If you cannot achieve satisfactory results with this procedure, disable the output
impedance control and use an external impedance network.
Rms voltage regulation can be used in conjunction with programmable output impedance to regulate the
rms value of the ac component of the output voltage when programmed impedances cause distortion with
nonlinear loads or reduced output voltage due to regulation effects.
Note that real-time voltage regulation will permit the load current to cause output voltage degradation
based on the programmed impedance and current drawn from the source, whereas rms regulation will
reestablish the rms value at the programmed level.
Output Coupling
Ac output coupling mode mimics a transformer-coupled output, working to maintain zero average
output voltage. This means that the output tries to remove any dc content on the output, whether the dc
content is generated from a programmed offset or results from transients with dc content. The ac output
coupling has a corner frequency of about 2 Hz, which will not prevent transient waveforms that may have
short-term dc content, but will regulate the waveform back to an average value of zero volts in the steady
state.
Dc output coupling mode is used to generate dc offset voltages or output transients that have net dc
components. In either mode of operation, the maximum voltage that the ac source can output is limited to
425 V peak.
The ac capability of the output is limited by VA (volt-amperes) rather than power (watts). The amount of
VA available to a load can be determined by examining figure 1-2. Full output VA is available with no
limitations except for the boundaries imposed by the maximum rms voltage of 300V, and the maximum
rms current, which is model-dependent. Note that large peak power transients can be delivered by the ac
source as earlier described under "Peak Current Capability"(Appendix A documents the ac source’s
specifications and supplemental characteristics.)