Fluke 731B User manual

731
B
Table of Contents
SECTION TITLE PAGE
1INTRODUCTION AND SPECIFICATTONS M
M. INTRODUCTION 1-1
1-
7. SPECIFICATIONS 1-2
2OPERATING INSTRUCTIONS 2-1
2-
LINTRODUCTION 2-1
2-3. SHIPPING INFORMATION 2-1
2-6. INPUT POWER 2-1
2-9. RACK INSTALLATION 2-2
2-11. OPERATING FEATURES 2-2
2-13. OPERATING NOTES 2-2
2-15. Guarded Operation 2-2
2-18. Battery Operation 2-4
2-20. OPERATION 24
2-21. Turn-On Procedure 2-4
2-23. Standard Cell Transfer 24
2-
25. Reference Voltage Modes 2-5
3THEORY OF OPERATION 3-1
3-
1. INTRODUCTION 3-1
3-3. OVERALL FUNCTIONAL DESCRIPTION 3-1
3-5. BLOCK DIAGRAM ANALYSIS 3-1
3-6. General 3-1
3-8. Charging Circuit 3-2
3-11. Reference Supply 3-2
3-14. Output Divider 3-2
{Continued on page ii
}

731
B
TABLE OF CONTENTS (Continued)
SECTION TITLE PAGE
4MAINTENANCE 4.I
4-1. INTRODUCTION 4.I
4-3. SERVICE INFORMATION ^i4.I
4-6. GENEIU\L MAINTENANCE 4*2
4-7, Access Information 4_2
4-9. Cleaning 4.2
4-11. Fuse Replacement 4.2
4-13. Service Tools 4.2
4-15. PERFORMANCE TEST !!.^!4-2
4-17. Line Regulation 4.2
4-18. Output Noise, DC to IHz 4.2
4-19. Output Noise, 1Hz to 1MHz 4^
4-20. Common Mode Rejection 44,
4-21. Isolation 4.5
4-22. Transfer Accuracy 4.5
4-23. CAUBRATION 4-6
4-
25. TROUBLESHOOTING !!!!!.'!!! 4-7
5LIST OF REPLACEABLE PARTS 5.I
TABLE OF CONTENTS 5.I
5-
1. INTRODUCTION !!!!
!5*2
5.4. HOW TO OBTAIN PARTS !!! !
!5^2
5-
7. USE CODE EFFECTIVITY UST !!!^!5-2
6OPTIONS AND ACCESSORIES
6-
i. INTRODUCTION ^j
6-3. RACK MOUNTING KITS !!!!!!!!! 6*1
7GENERAL INFORMATION 7.I
8SCHEMATIC DIAGRA.MS g.j
ii

731
B
List of Illustrations
'III"'*,I—
FIGURE TITLE PAGE
1-
1Outline Drawing j-3
2-
1731 BControls, Indicators, and Connectors 2-2
2-2 Guard Connections 2-4
2-
3Standardizing the 73 IB 2-5
3-
173 IB Simplified Block Diagram 3-1
3-
2Reference Amplifier 3-2
4-
1Adjustment Locations 4-3
4-2 Equipment Connections for Line Regulation, DC to 1Hz Output
Noise, and Transfer Accuracy Tests 4A
4-3 Equipment Connections for 1Hz to 1MHz Output Noise Test ..,.4-4
4-4 Equipment Connections for Common Mode Rejection Test 4-5
4-5 Equipment Connections for Divider Adjustment 4-6
4-
6Equipment Connections for Absolute Voltage Adjustments 4-7
5-
173 IB Final Assembly 5-4
5-2 Reference Regulator PCB Assembly 5-7
5-
3Power Supply and Adjustment PCB Assembly 5-10
6-
1Rack Mounting Configurations 6-1
6-2 Rack Ear Installation 6-2
6-3 Dual, Triple, and Quad Mounting 6-3
B-1 73 IB DC Reference Standard (73 IB-1011) 8-3
iii

TABLE TITLE PAGE
2-1 73 IB Controls, Indicators and Connectors 2-3
4-1 Required Test Equipment 4-1
4-2 73 IB Calibration 4-6
7-1. List of Abbreviations &Symbols 7-1
7-2. Federal Supply Codes for Manufacturers 7-3
7-3. Fluke Technical Centers y.jO
7-4. Sales Representatives 7-1
1
7-5. Sales Representatives -International 7-13
IV

731
B
Section 1
Introduction &Speci ications
1-1. INTRODUCTION
1-2. The Model 731 BDC Reference Standard is an ultra-
stable dc power supply which, when standardized, is cap-
able of providing avariety of precision output voltages
with standard cell accuracy. The 73 IB will furnish basic
dc voltage outputs of lOV, IV, AE (000 to 999 pV),
1.018 +AE, and 1.019 +AE.
1-3. The desired voltage mode is selected using afront
panel function switch and the value of AE is adjustable us-
ing a10-turn linear potentiometer. The front panel AE con-
trol includes a3digit turn counter to indicate the selected
value of AE, i.e., 000 to 999 pV. The counter is equipped
with alocking lever to prevent accidental changing of ase-
lected AE setting,
1-4. Afront panel guard connection is provided for use
in reducing errors causedby common mode voltages. The
guarded internal circuitry is isolated from the chassis and
earth ground.
1-5. Power to operate the 73 IB can be derived from
either an internal battery pack for field or portable use, or
from the ac power line for bench use. Afront panel meter
indicates the relative charge level of the internal battery
pack during portable use. The AC line requirements are
1I5/230V ac,50to 400 Hz.
1-6. The 73 IB is supplied with non-marring feet for
bench or field use. It may also be conveniently mounted in
astandard 19” equipment rack using one of the rack mount-
ing accessory kits shown in Table 1-1.
Table M. ACCESSORY RACK MOUNTING KITS
MODEL NUMBER MOUNTING
CONFIGURATION
M03-201-601
M03-202-603
M03-206-604
M03-205-605
One 731 B, Offset mounting
Two731B's, Side-by-side
Three 731 B's, Side-by-side
Four 731 B's, Side-by-side
1-1

731B
1-7. SPECIFICATIONS
Output Voltage
Range
10.0
1.0
1.018 +AE
1.019 +AE
AE
Output
10.0V dc
1.OV dc
1.018 to 1.018999V dc
1.019 to 1.019999V dc
0to 999 liV dc with
1juV resolution
Output Accuracy: Absolute accuracy at 23°C +1°C
after 30 minute warm-up
Range Period
10V
IV
1.01 8+ -Ae
Ae
30 days 90 Days 1Year
+10 PPM
+10 PPM
+10 PPM
+15 PPM
+15 PPM
+15 PPM
+30 PPM
+30 PPM
+30 PPM
+2uV
Transfer Accuracy: 4Hr
Between standard cells on 1.018V +2ppm
AE or 1.019V +AE ranges:
Between standard cell and IV 3ppm
output:
Between 10V output and standard 5ppm
ceil or IV output:
Temperature Coefficient:
Less than 1PP^/i/C^ 10°Cto45°C
Less than 2PPM/c“, 0'’C to lO^C and 45°C to 55°C
Output Current:
IV, 1.018V, 1.019V Ranges:
The Reference Transfer Standard is designed to per-
form as astandard cel! and therefore is intended to
operate into ahigh impedance on the IV, 1.018V and
1.019V ranges drawing minute currents. This impe-
dance is usually infinity as in potentiometric circuits,
or, in other applications should be at least 100 Meg-
ohms to prevent source loading.
Source Resistance:
10V Range <0.0717
IV, 1.018V. 1.019V,
AE Ranges: <1kS7
Output Protection:
The output may be shorted indefinitely without
damage to instrument.
Line Regulation:
Less than 1PPM for +10% line variation.
Ripple &Noise:
Less than 1PPM P-P dc to 1Hz
Less than 20 juV RMS 1Hz to 1MHz
Except <70 juV RMS @10V output
Common Mode Rejection:
120 db at DC
100 dbateO Hz
85 db at 400 Hz
Isolation:
Output may be floated up to 500 VDC between
chassis ground and guard.
Calibration Adjustment:
10 Volt Range:
The 10 volt range is used in applications where some
degree of loading is placed on the Reference Transfer
Standard such as aKelvin Varley Divider or other re-
sistance networks.
Loading Effect on the 10V Range
;
Load R. Output Change (PPM)
100 M12 0
10 M17 0.005 «=0
1M17 .05
0.1 M17 .5
10 KQ 5
Separate internal adjustments for the 5output vol-
tages. Front panel adjustment common to ail voltages
including the 10.000V output. Basic reference adjust-
ments accessible from the front panel.
Temperature/Humidity:
+0°C to +55°C operating.
—40'^C to +60°C non-operating.
Up to 70% RH for temperatures <35°C
Shock &Vibration:
Meets requirements of MIL-T-21200L
1-2

731
B
Terminals:
Four five-way binding posts for positive, negative,
ground and guard. Positive and negative are solid
copper with gold flash.
Battery Operation:
Rechargeable nickel-cadmium batteries provide at least
30 hours of continuous operation.
input Power:
115V or 230V +10V ac, 50 to 400 Hz single phase or
interna! battery operation.
6watts maximum, 120 Ma maximum
Size:
SVa" high X4%" wide x12" deep. (8.8 x10.7 x30.4
(8.8 X10.7 X30.4 cm)
Weight:
5lbs (2.26 kg)
Figure 1-1. 7318 OUTLINE DRAWING

731 B
2-1. INTRODUCTION
2-2. This section of the manual contains infonnation re-
garding instaliation and operation of the Model 731 BDC
Reference Standard. It is recommended that the contents of
this section be read and understood before any attempt is
made to operate the 73 IB. Should any difficulties arise
during operation, please contact your nearest John Fluke
ISales Representative or the John Ruke Mfg. Co., Inc.,
P.O. Box 43210, Mountlake Terrace, WA 98043; telephone
(206) 774-221 1. Alist of Sales Representatives is located
in Section 7of this manual.
2-3. SHIPPING INFORMATION
2-4, The 73 1Bis packaged and shipped in afoam -
packed container. Upon receipt of the instrument, athor-
ough inspection should be made to reveal any possible
shipping damage. Special instructions for inspection and
claims are included in the shipping carton.
2-5. If reshipment of the equipment is necessary, the
original container should be used. If the original container
is not available, anew container can be obtained from tlie
John Fluke Mfg. Co., Inc. Please reference the equipment
model number when requesting anew shipping container.
2-6. INPUT POWER
2-7 .The 73 1Bcan be operated from a115 or 230V ac,
50 to 400 Hz power line. Before connecting the instrument
to the power line, check and, if necessary, set the instrument
to operate at the local line voltage as follows:
2-1

731B
a. RemoVethe to pCOve rfroiri the73iBa n d1oc ate
the input power selection switch on the inside of
the 73 IB.
b. Set the slide switch to the desired operating vol-
tage, 115(white dot) or 230 (red dot).
c. Install the proper fuse (i.e., AGC ViK for 115V ac
and AGC %A for 230V ac) in the rear panel fuse
holder.
2-8. The rear panel input power connector is athree
prong, U-ground connector which permits the in-
strument to be connected, via the power cord, to
the appropriate line power. The offset prong on
this connector is connected to the 73 IB chassis
and power supply, and should be connected, via
the power cord, to ahigh quality earth ground.
2-9. RACK INSTALLATION
2-10, The 73 1Bis designed for bench-top use or for in-
stallation in astandard 19-inch equipment rack, using one
of the optional accessory rack mounting kits. Information
regarding rack installation procedures is given in Section 6
of this manual.
2-11. OPERATING FEATURES
2-12. The 731 Bcontrols, indicators and connectors
are shown in Figure 2-1, and described in Table 2-1.
2-13. OPERATING NOTES
2-14, The following paragraphs describe various condi-
tions which .should be considered before operating the 73 IB.
2-15. Guarded Operation
2-1 6, The 73 IB is equipped with aguard that isolates its
internal circuitry from the chassis and earth ground. A
GUARD terminal is provided on the Torntpanel, and when
used, greatly reduces errors caused by common mode vol-
tages. In general, guarded operation will be necessary under
the following conditions:
a. Wlren apotential exists between equipment power
line grounds.
b. Wlien long connecting leads are used to contact a
higli impedance load.
2-2
Figure 2-1. 731 BCONTROLS, INDICATORS AND CONNECTORS

7318
Table 2-1. 731B CONTROLS. INDICATORS AND CONNECTORS
REF.
NO. NAME FUNCTION
1POWER Switch Switches the instrument on and off. When in the ON position, the Battery
Charge Meter indicates line operation or battery charge level. Switch position
can only be changed while activator is pulled out.
2CAL Potentiometer Provides the adjustment necessary to standardize the 731 B{all modes) to an
externa! standard cell.
3Battery Charge
Meter
Indicates power -on {LINE OPR) when the instrument is being operated
from the power line. During battery operation, the meter indicates the
relative charge level of the internal battery pack.
4Mode Switch Selects the operating mode used to supply voltage to the +and -OUTPUT
terminals:
10V .... Provides afixed 10V dc output.
TV .... Provides afixed IV dc output.
AE .... Provides an adjustable+000 to +999 /LtVdc output
in 1^V steps.
1.018 +AE ..Provides an adjustable +1.018000 to +1.018999 Vdc
output. This mode is used to standardize to 731
B
to astandard cell whose voltage falls within the
adjustable range.
1.019 +AE. .Provides an adjustable +1.019000 to +1.0 19999V dc
output. This mode is used to standardize the 731
B
to astandard cell whose voltage falls within the ad-
justable range.
5AE vernier
Control Avernier control which provides the manual AE adjustment. The control
is equipped with athree decade digital readout to permit exact settings
from 000 to 999 juV dc.
6OUTPUT
Terminals
Provides front panel connection to the 731 Boutput and guard circuits.
+“Voltage output terminals
GUARD Provides connection to the internal
guard circuit and is used to reduce
the effects of common mode voltages.
7Input Power
Connector
Provides the means of connecting the instrument through the power cord
to line power.
8Ground Terminal Provides aconvenient ground point during battery operation.
9Fuse Protects the ac input section of the power supply.
2-3

731B
c. When operating the instrument in the presence of
high level radiated noise, e. g., stay fields at the
power line frequency.
2-17. One of the most common cases requiring guarding
is that of differences in power line grounds. When the
731 Bis connected to another instrument, with both instm-
ments grounded through their respective power cords, a
potential difference may exist between the power line
grounds of these two instruments. This potential difference
can cause circulating ground currents which could cause
errors in the output voltage. To prevent these errors from
occurring, the 73 IB GUARD terminal should be connected
to the load in such amanner as to provide aseparate path
for circulating ground currents. For proper connection,
connect GUARD terminal directly to grounded side of
load, at the load. Figure 2-2 illustrates correct GUARD
terminal connection and the rerouted ground currents.
2-18. Battery Operation
2-19. The rechargeable nickel-cadmium battery provides
at least 30 hours of continuous operation before recharg-
ing is required. Batteries are automatically trickle charged
whenever the instrument is operating from the ac line. Re-
charging of completely discharged batteries requires ap-
proximately 12 hours.
NOTE
Aground terminal on the rear of the 73IB pro-
vides aconvenient method ofgrounding the in-
strument during battery operation.
Figure 2-2. GUARD CONNECTION
2-20. OPERATION
2-21. Turn-On Procedure
2-22. Use of the following procedure is suggested for
initial turn-on of the 73 IB:
a. Connect the instrument to ac line power (See para-
graph 2-6). This step is not necessary if battery
operation is desired.
b. Set the POWER switch to the ON position.
NOTE
The POWER switch actuator must he pulled out
before the switch position can be changed.
c. Ensure that the instrument is energized by observ-
ing the indication shown on the battery charge
meter. For line operation, the meter should indi-
cate BAT OK. If the meter indication falls below
BAT OK, the battery pack should be recharged.
2-23. Standard Cell Transfer
2-24. When standardized to an external standard cell,
the selected 73 IB output will be within 2ppm of the
standard cell voltage. Stability is better than 10 ppm
per month. Use the following procedure to standardize
the 73 IB.
a. Energize the 73 IB and allow a30-minute warm-
up period.
b. Obtain acertified standard cell and note its
voltage.
c. Set the mode switch to (1.018 +AE) or (1.019
+AE) whichever includes the equivalent of the
standard cell voltage.
d. Connect the standard cell and anull detector
(Fluke 845AB or equivalent) to the 73 IB as
shown in Figure 2-3.
e. Adjust the AE control so that the mode switch
setting pluse the AE setting is equal to the stand-
ard cell voltage.
f. Adjust the front panel CAL potentiometer for an
optimum null.
2-4

731B
g-
2-25.
2-26.
731B
NULL DETECTOR
Figure 2-3. STANDARDIZING THE 731 B.
Disconnect the standard cell and the null detector aAE, a1volt or a10 volt output with standard cell trans-
form the 73 IB OUTPUT terminals. fer accuracies of 2ppm, 3ppm or 5ppm, respectively. For
example, standardizing the 73 IB to astandard cell having an
Reference Voltage Modes absolute accuracy of 3ppm would provide a10 volt refer-
ence output which is accurate to 8ppm (3 ppm standard cell
Astandardized 73 IB can be used to provide either accuracy -i- 5ppm 73 IB transfer accuracy) or 0.0008%.
2-5/2-6

731B
Section 3
Theory of Operation
3-1. INTRODUCTION
3-2. This section of the manual contains an overall func-
tional description followed by adetailed block diagram analy-
sis of the Model 73 IB DC Reference Standard. Simplified
block diagrams and circuit diagrams are included as neces-
sary, to supplement the text.
3-3. OVERALL FUNCTIONAL DESCRIPTION
3-4. The 73 IB, is an ultra-stable dc power supply which,
when standardized, is capable of providing either astandard
1volt, 10 volt or 000 to 999 microvolt output. Tie desired
output voltage is selected by the Mode switch, and in the
AE mode the output is adjustable using the AE vernier con-
trol. The resistor networks in the Output Divider scale a
fixed precision dc voltage from the Reference Supply to
provide the output voltage selected by the Mode switch set-
ting. Operating voltage for the Reference Supply is derived
from the Charging Circuit. Either ac line power or the bat-
tery pack can be used to provide the unregulated operating
voltage to the Reference Supply. Wlien using the ac line,
the charging circuits also charge the battery pack.
3-5. BLOCK DIAGRAM ANALYSIS
3-6. General
3-7. Ablock diagram analysis of the functional circuits
of the 73 1Bis given in the following paragraphs. The cir-
cuits described correspond to the functional blocks defined
in Figure 3-1. Detailed schematics are included in Section 8
of this manual.
Figure 3-1. 731 BSIMPLIFIED BLOCK DIAGRAM.
5/75 3-1

731B
3-8. Charging Circuit
3-9. The Charging Circuit is included on the A3 Power
Supply PCB and corrsists of afull wave rectifier CRl 2, series
pass transistor Q3 and the associated components. The func-
tion of the charging circuit is two-fold, and depends on
whether the 73 1Bis being operated from the ac power line
or the battery pack. In the line power configuration, the
output of transformer A4T1 is rectified by CRl 2before
being used to supply the raw input voltage to the series-pass
regulator Q3. Since the rectified output of CRl 2exceeds
the battery pack voltage, atrickle charge is delivered to the
batteries, through CR5 and R30. Wlien the 731 Bis discon-
nected from the ac power line, it is operated from the in-
ternal Ni-cad battery pack. In this configuration, the series
regulator is by-passed and the battery output is delivered
directly to the output of the charging circuit via diode CR8.
3-10. The meter circuit is calibrated to indicate the rela-
tive battery charge level during battery operation, and full
scale during line operation. Resistors R31 and R32 are used
to set the meter indication during battery operation. For
line operation diode CR7 and R34 provide the extra drive
necessary for afull scale indication.
3-11. Reference Su pply
3-12. The Reference Supply (included on the Refer-
ence Regulator PCB) consists of acompensated zener refer-
ence amplifier U2, operational amplifier Ul, transistors Q1
and Q2, and their associated circuitry. The function of the
Reference Supply Is to regulate the output voltage supplied
by the charging circuit, and to provide aprecisely replated
+10V dc output signal. Reference amplifier U2 functions
as the primary element in the Reference Supply and is shown
in Figure 3-2. It contains asilicon NPN transistor connected
in series with azener diode and both are mounted on a
common substrate which is enclosed in asingle envelope.
The reference voltage, Vref, is the sum of the zener vol-
tage, and the transistor’s base-to-emitter voltage ^be-
Temperature variations affecting are compensated for
by corresponding changes in Vj^g.
3-13. In operation, the Reference Supply acts as asimple
series pass replator, with Q1 acting as the series pass ele-
ment. Replation is accomplished by the action of U2 which
compares its internal reference voltage witli the output vol-
tage and adjusts the base drive of Q1 ,via amplifier Ul ,until
both voltages are equal. Short circuit protection is provided
by current sensing resistor R28 and transistor Q2. Poten-
tiometer Rl 1is the front panel CAL adjust used to stand-
ardize the reference supply. The output of the supply,
when standardized, is exactly -MOV dc.
3-14, Output Divider
3-15. The 73 1Aoutput voltage is selected by means of the
front panel mode switch and aseries of resistive dividers at-
tached to the Reference Supply output. In the lOV mode
the Reference Supply output is connected directly to the
OUTPUT terminals. In all other modes the +I0V reference
voltage is reduced by avoltage divider before being made
available at the OUTPUT terminals. Separate calibration
potentiometers are provided for each of the selectable modes.
The IV output is adjusted by R19andthe 1.018 and 1.019
Voutputs are adjusted by R17 and R15, respectively. The
AE output is calibrated by R24, and is adjustable from 000
to 999 pV using the front panel AE vernier control (AlRl).
In the I.0I8 +AE and 1.019 +AE modes the AE divider is
operated in conjunction with the 1.018 and 1.019 dividers.
In the AE mode, the AE divider operates independently.
3-2

731B
Section 4
Maintenance
4-1. INTRODUCTION
4-2. This section of the manual contains maintenance
mformation for the Model 73 IB DC Reference Standard.
This includes service information, general maintenance, per-
formance test, calibration and troubleshooting information.
The performance test is recommended as apreventative
maintenance tool, and should be executed every 90 days to
verify proper instrument operation within the specifications
given in Section 1. Acalibration interval of 90 days is rec-
omended to ensure that the instrument remains within these
specifications. Table 4-1 lists the equipment required for
the performance test and calibration.
4-3. SERVICE INFORMATION
4-4. Each instrument that is manufactured by the John
Buke Mfg. Co., Inc. is warranted for aperiod of one year
upon delivery to the original purchaser. The WARRANTY
is given on the back of the title page located in the front of
the manual.
4-5. Factory authorized calibration and service for each
Buke product is available at various world-wide locations.
Acomplete list of these service centers is included with the
Table 4-1. REQUIRED TEST EQUIPMENT
EQUIPMENT
NOMENCLATURE RECOMMENDED
EQUIPMENT
Null Detector Fluke Model 845AB
DC Differential
Voltmeter Fluke Model 895A
True RMS Differ-
ential Voltmeter Fluke Model 93 IB
DC Voltage Source Fluke Model 341
A
DVM Calibrator
Standard Cell Guildline Instru-
ments Mode! 9152/P4
XI 000 Amplifier —
Voltage Divider Fluke Model 720A
Kelvin-Vartey Voltage
Divider
Low-Thermal
Switch Leeds &Northrop
Type 3702 Tapping Key
Autotransformer General Radio
W5MT3A or W10MT3A
4-1

731B
WARRANTY. Shipping information is given in the operat-
ing instructions section of this manual. If requested, an es-
timate will be provided to the customer before work is be-
gun on instruments that are beyond the warranty period.
4-6. GENERAL MAINTENANCE
4-7. Access Information
4-8. Use the following procedure to gain access to the
interior of the instrument (See Figure 4-1);
a. Remove the top dust cover.
b. Remove the guard cover.
c. Remove the bottom dust cover.
4-9. Cleaning
4-10. Clean the instrument periodically to remove dust,
grease and other contamination. Use the following proce-
dure:
a. Clean the surface of all PCB’s using clean dry air at
low pressure (< 120 psi). If grease is encountered,
spray with Freon T.F. Degreaser and remove grime
with clean dry air at low pressure.
b. Clean the front panel with asoft cloth dampened
with amild solution of detergent and water.
CAUTION!
Do not use aromatic hydrocarbons or chlorin-
ated solvents on the front panel of the 73 IB.
4-11. Fuse Replacement
4-12. The power fuse FI is located on the rear panel of
the Model 73 IB. If replacement is necessary, use the fol-
lowing rated fuses:
a. 115 Volt operation -AGC %Ampere
b. 230 Volt Operation —AGC 14 Ampere
4-13. Service Tools
4-44. No special tools are required to maintain or repair
the 73 IB.
4-15. PERFORMANCE TEST
4-16. The performance test is designed to verify the over-
all operation of the 73 IB. This test can be used as an accep-
tance check and/or periodic maintenance check. Table 4-1
lists the ecgiipment required to perform this test. If the
unit fails any part of the performance test, corrective
action is indicated. Tests should be conducted at an ambient
temperature of 25°C ±5°C and arelative humidity of less
than 70%. Allow a30 minute warm-up period prior to con-
ducting the performance test.
4-17. Line Regulation
a. Connect equipment as shown in Figure 4-2.
b. Adjust the autotransformer for an output voltage
of 115V ac.
c. Zero the 845 AB on the 1microvolt range, then set
it to the 10 microvolt range.
d. With the test switch open, adjust 73 1Boutput to
equal the standard cell voltage.
e. Close the switch and adjust 73 IB output for null
on the 845AB.
f. Vary autotransformer output from 115 to 105V ac
and from 115 to 125V ac. The 845AB indication
should not change more than ±1 microvolt.
g. Set the variac output to 11 5V ac.
4-18. Output Noise, DC to 1Hz.
a. Connect equipment as shown in Figure 4-2.
b. Zero the 845AB on the 1microvolt range, then set
it to the 10 microvolt range.
c. Adjust 73 IB output for null on 845 AB.
d. Observe the random voltage excursions indicated
on the 845AB over a10 second period. Excursions
should be less than 1microvolt peak to peak.
4-2

731
B
4-3

731B
731B
AUTO- .115 VAC
4
-4"TRANSFORMER 50-400 Hz
1"845AB
——
STANDARD CELL LOW THERMAL
SWITCH NULL DETECTOR
Piiure 4-2 EQUIPMENT CONNECTIONS FOR LINE REGULATION, DC TO IHz OUTPUT NOISE, AND TRANSFER
ACCURACY TESTS.
4-19, Output Noise, 1Hz to 1MHz
a. Coiniecl equipment as shown in Figure 4-3.
b. Set 93 IB range to 100 millivolts, mode switch to
TVM XI.
c. Set 73 IB output to 1.018000 volts. The 93 IB
should indicate less than 20 millivolts rms, which
represents 20 microvolts output from the 73 IB.
4-20. Common-Mode Rejection
a. Connect equipment as shown in Figure 4-4.
b. Set 34 1Afor zero volts output.
c. Set 73 IB output to 1.018000 volts.
d. Set 895Arange to 1volt, null sensitivity to 100
microvolts, and readout dials for null indication.
e. Set 341 Aoutput to 100 volts. The 895 Ameter
indication should be zero ±100 microvolts.
Figure 4-3. EQUIPMENT CONNECTIONS FOR 1HZ TO 1MHZ OUTPUT NOISE TEST.
4-4

731
B
731B
895A ••••
rti
Figure 4-4. EQUf PMENT CONNECTIONS FOR COMMON-MODE REJECTION TEST.
4-21. Isolation
a. Turn off the 73 1Band disconnect it from the pow-
er line.
b. Connect the negative output terminal of the 341 A
to the guard terminal of the 73 IB and the positive
output terminal of the 341 Ato case (ground) of
the 73 IB.
c. Set 341 Aoutput to 500 volts. The 341 Ameter
should indicate no discernable current flow.
d. Repeat steps (b) and (c) for the positive output ter-
minal of the 73 IB.
e. Repeat steps (b) and (c) for the negative output
terminal of the 73 IB,
4-22, Transfer Accuracy
a. Connect equipment as shown in Figure 4-2.
b. Zero 845 AB on the 1microvolt range, then set it
to the 10 microvolt, range.
c. With the switch open, adjust 731 Boutput to equal
standard cell voltage.
d. Close the switch and adjust 73 IB output for null on
the 845AB.
e. Lock the AE control on the 73 IB.
f. Open the test switch, remove all test leads from the
setup, and allow the 73 IB to operate for 20 min-
utes,
g. Reconnect equipment and check 731 Boutput for
null against standard cell. The 845 AB should in-
dicate less than ±2 microvolts deviation from null
(zero).
4-5