Fluke 341A User manual

Notwithstanding any provision of any agreement the following warranty is exclusive:
The JOHN FLUKE MFG. CO., INC., warrants each instrument it manufactures to be free from defects in material and
workmanship under normal use and service for the period of 1-year from date of purchase. This warranty extends only
to the original purchaser. This warranty shall not apply to fuses, disposable batteries (rechargeable type batteries are
warranted for 90-days), or any product or parts which have been subject to misuse, neglect, accident, or abnormal
conditions of operations.
In the event of failure of aproduct covered by this warranty, John Fluke Mfg. Co., Inc., will repair and calibrate an
instrument returned to an authorized Service Facility within 1year of the original purchase; provided thewarrantor’s
examination discloses to its satisfaction that the product was defective. The warrantor may, at its option, replace the
product in lieu of repair. With regard to any instrument returned within 1year of the original purchase, said repairs or
replacement will be made without charge. If the failure has been caused by misuse, neglect, accident, or abnormal
conditions of operations, repairs will be billed at anominal cost. In such case, an estimate will be submitted before
work is started, if requested.
THE FOREGOING WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS,
OR ADEQUACY FOR ANY PARTICULAR PURPOSE OR USE. JOHN FLUKE MFG. CO., INC.. SHALL
NOT BE LIABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WHETHER IN
CONTRACT, TORT, OR OTHERWISE.
If any failure occurs, the following steps should be taken:
1. Notify the JOHN FLUKE MFG. CO., INC., or nearest Service facility, giving full details of the difficulty, and
include the model number, type number, and serial number. On receipt of this information, service data, or
shipping instructions will be forwarded to you.
2. On receipt of the shipping instructions, forward the instrument, transportation prepaid. Repairs will be
made at the Service Facility and the instrument returned, transportation prepaid.
SHIPPING TO MANUFACTURER FOR REPAIR OR ADJUSTMENT
All shipments of JOHN FLUKE MFG. CO., INC., instruments should be made via United Parcel Service or "Best Way"
prepaid. The instrument should be shipped in the original packing carton; or if it is not. available, use any suitable
container that is rigid and of adequate size. If asubstitute container is used, the instrument should be wrapped in paper
and surrounded with at least four inches of excelsior or similar shock-absorbing material.
CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL PURCHASER
The instrument should be thoroughly inspected immediately upon original delivery to purchaser. All material in the
container should bechecked against the enclosed packing list. The manufacturer will not be responsible for shortages
against the packing sheet unless notified immediately. If the instrument is damaged in any way, aclaim should be filed
with the carrier immediately. (To obtain aquotation to repair shipment damage, contact the nearest Fluke Technical
Center.) Final claim and negotiations with the carrier must be completed by the customer.
The JOHN FLUKE MFG. CO., INC, will be happy to answer all applications or use questions, which will enhanceyour
use of this instrument. Please address your requests or correspondence to: JOHN FLUKE MFG. CO., INC., P.O. BOX
43210, MOUNTLAKETERRACE, WASHINGTON 98043, ATTN: Sales Dept. For European Customers: Fluke (Holland)
B.V., P.O. Box 5053, 5004 EB, Tilburg, The Netherlands.
'For European customers, Air Freight prepaid.
John Fluke Mfg. Co., Inc., P.O. Box 43210, Mounifake Terrace, Washington 98043
Rev. 4/80

Section Title Page
IINTRODUCTION AND SPECIFICATIONS I-I
1-1. Introduction 1-1
1-5. Electrical Specifications 1-1
1-6. Environmental Specifications 1-2
1-7. Mechanical Specifications 1-3
1-
8. General Specifications 1-3
II OPERATING INSTRUCTIONS 2-1
2-
1. Introduction 2-1
2-4. Operating Features 2-1
2-6. Controls, Terminals and Indicators 2-1
2-8. Input Power Requirements 2-1
2-10. Preliminary Operation 2-1
2-12. AC Line Connections 2-1
2-14. Sense Connections 2-1
2-18. Current Limit. Operation 2-5
2-20. Overload Protection 2-5
2-23. Mechanical Zero Adjustment 2-5
2-25.. Operation as aVoltage Calibrator 2-5
2-
27. Applications 2-6
2-29. Operation as a Differential Voltmeter 2-6
2-
31. Operation as a10 ppm Source 2-6
III THEORY OF OPERATION 3-1
3-
1. Introduction 3-1
3-3. Block Diagram Analysis 3-1
3-12. Circuit Analysis 3-3
3-
13. +15 Volt Reference and Auxiliary Supplies 3-3
3-16. Chopper-Stabilized Amplifier 3-3
3-20. Series Regulator 3-3
3-23. Controlled Current Limiter 34
3-27. Negative Voltage Limiter 34
3-29. Sink Supply and Crowbar 34
3-34. Control Circuit 3-5
3-38. High Voltage Power Supply 3-6
340. Meter Circuit 3-6
3-42. Beta String 3-6
(continued on page ii)
t

TABLE OF CONTENTS, continued
Section Title Page
IV MAINTENANCE 4-1
4-1. Introduction
4-3. Service Information
4-6. Test Equipment
4-8. General Maintenance
4-9. Maintenance Access
4-13. Adjustment Locations
4-15. Cleaning
4-18. 115/230 Volt Conversion
4-20. Fuse Replacement
4-22. Lamp Replacement
4-24. Performance Tests
4-26. Line Regulation
4-28. Load Regulation
4-30. Ripple
4-32. Output Voltage Accuracy
4-36. Troubleshooting
4-39. Test Point Resistance Check ..,.
4-41. Standby Test
4-43. Auxiliary Supply Voltages
4-45. Power-On Test
4-47. Chopper Amplifier
4-49. Series Regulator
4-51. Controlled Current Limiter
4-53. Crowbar
4-55. High Voltage Power Supply
4-57. Beta String
4-59. Panel Meter
4-61. Model 341 ACalibration
4-63. Preliminary Operations
4-64. Reference Voltage Adjustment . . .
4-65. Zero Output Adjustments
4-66. Beta String Linearity Adjustments
4-67. Range Adjustments
4-68. Calibration Verification
4-1
4-1
4-1
4-1
4-3
4-3
4-4
4-5
4-5
4-5
4-6
4-6
4-6
4-7
4-8
4-8
4-8
4-8
4-9
4-30
4-11
4-11
4-12
4-12
4-3 2
4-13
4-13
4-14
4-14
4-14
4-14
4-14
4-34
4-3 5
(continued on page Hi)

TABLE OF CONTENTS, continued
Section Title Page
4-70. Model 343A Preliminary Calibration 4-15
4-72. Preliminary Operations 4-15
4-73. Reference Voltage Adjustment 4-16
4-74. Zero Output Adjustments 4-16
4-75. Beta String Linearity Adjustments 4-16
4-76. Temperature Stabilization 4-17
4-
77. Model 343A Final Calibration .. .4-17
4-79. Zero Output Adjustments 4-17
4-80. Beta String Linearity Adjustments 4-17
4-83. Range Adjustments 4-19
4-84. Calibration Verifications 4-20
VLIST OF REPLACEABLE PARTS 5-1
5-
1. Introduction .5-1
5-3. Column Description ‘
. . .5-1
5-5. How To Obtain Parts 5-2
5-8. List of Abbreviations 5-2
5-9. Serial Number Effectivity 5-45
7GENERAL INFORMATION 7-1
8SCHEMATIC DIAGRAMS 8-1
iii

Figure Title
Frontispiece Model 341A and Model 343A DC Voltage Calibrators vi
1-
1. Model 341 A/343A Outline Drawing 1-3
2*1. Controls, Terminals and Indicators (Sheet 1of 2) 2-2
2-
1.Controls, Terminals and Indicators (Sheet 2of 2) 2-3
2-2. Nomograph of Voltage Drop in Load Wires 2-4
2-3. Differential Voltmeter 2-6
2-
4. Operation as a10 ppm Source 2-7
3-
1. Model 341A/343A Block Diagram 3-1
3-
2. Basic Instrument Circuitry 3-2
4-
1. Test and Calibration Equipment 4-2
4-2. Model 341 AAdjustment Locations 4-3
4-3. Model 343A Adjustment Locations 4-4
4-4. 115/230 Volt Conversion 4-5
4-5. Ripple Specifications 4-7
4-6. Multivibrator Signal -- TP9 4-10
4-7. Chopper Amplifier Signal -- TP 10 4-11
4-8. High Voltage Power Supply Output Voltages 4-13
4-9. Beta String Switching Requirements 4-13
4-10. 341 ALinearity Adjustments 4-15
4-11. 341A Output Voltage Requirements 4-15
4-12. Model 343A Preliminary Linearity Adjustments (Sheet 1of 2) 4-16
4-12. Model 343A Preliminary Linearity Adjustments (Sheet 2 of 2) 4-17
(continued on page v
)

341
A
343A
LIST OF ILLUSTRATIONS, continued
Figure Title Page
4-13. Beta String Linearity Test Setup 4-17
4-14. 343ALinearity Adjustments -Deck B 4-18
4-15. 343ALinearity Adjustments -Deck A4-18
4-16. Range Adjustment and Calibration Verification Test Setup 4-19
4-
17. Model 343A Output Voltage Requirements 4-20
5-
1. 341 ADC Voltage Calibrator (Sheet 1of 2) 54
5-1. 341 ADC Voltage Calibrator (Sheet 2of 2) 5-5
5-2. Front Panel Assembly 5-6
5-3. Rear Panel Assembly (341 A) 5-7
5-4. Main P/C Assembly (Left Hand Side) 5-12
5-5. Main P/C Assembly (Right Hand Side) 5-13
5-6. Reference P/C Assembly (341 A) 5-29
5-7. Sample String P/C Assembly 5-32
5-8. 343A DC Voltage Calibrator (Sheet 1of 2) 5-35
5-8. 343A DC Voltage Calibrator (Sheet 2of2) 5-36
5-9. Front Panel Assembly (343A) 5-37
5-10. Rear Panel Assembly (343A) 5-38
5-11. Reference P/C Assembly 5-40
5-12. Sample String P/C Assembly 543
v

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MODEL 343
A
$
33
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1-1. INTRODUCTION
1-2. The Fluke Model 341 Aand Model 343A DC
Voltage Calibrators provide dc voltages of 0to 1100 volts
in three ranges. Voltages are selected by eleven-position
decade switches, which provide in-line, digital readout of
the instrument output voltage. The Model 341 Aemploys
six-dial readout, with 1ppm resolution, and the Model
343A employs seven-dial readout, with 0.1 ppm resolution.
Model 343A:
Range (volts
10
100
1000
RESOLUTION
Model 341 A:
Model 343A:
Output (volts)
0to i1.1 111 10 (1 uv steps)
0to 111.11110 (10 uv steps)
Oto 1111.1110(100 uv steps)
1ppm of range (10 uv maximum)
0.1 ppm of range (1 uv maximum)
1-3. Acontrolled current limiter, afixed current limit-
er, and an electronic crowbar circuit provide protection
against instrument malfunction and operator error. Output
current or voltage, depending on function desired, are con-
tinuously monitored by afront panel meter.
1-4. The instruments are designed for rack-mount
installation, using the mounting brackets supplied, and are
equipped with resilient feet and tilt-down bail for field or
bench use.
1-5. ELECTRICAL SPECIFICATIONS
ACCURACY OF OUTPUT
NOTE: The following accuracy specifications apply after
(1 hour) warmup at standard reference conditions of
23°C±5°C for the Model 341Aand 23<) C±1°C for the
Model 343A, up to 70% relative humidity, constant, line
voltage, and constant load.
Model 341 A:
Range Accuracy (whichever is greater)
10V ±0.01% of setting or ±0.0003% of range
100 V±0.01% of setting or ±0.0002% of range
1000 V±0.01% of setting or ±0.0002% of range
OUTPUT VOLTAGE
Model 341 A: 0to 1111.110 volts dc
Model 343A: 0to 1111.1110 volts dc
VOLTAGE RANGES
Range (volts)
10
100
1000
Output (volts)
0to 11.11110 (10 uv steps)
0to 111.1110 (100 uv steps)
0to 1111.1 10 (1 mv steps)
Range Accuracy (whichever is greater)
10V ±0.003% of setting or ±0.0003% of range
100 V±0.003% of setting or ±0.0001% of range
1000 V±0.003% of setting or ±0.0001% of range
TEMPERATURE COEFFICIENT OF OUTPUT
Model 341 A: Less than (5 ppm of setting +0.1 ppm of
range +2 uv) per °C from +15° to +35°C. Less than (8
ppm of setting +0.1 ppm of range +2 u.y) per °C from 0°
to +50°C.

341
A
343A
Model 343A: Less than (3 ppm of setting +0.1 ppm of
range +2 uv) per °C from +15° to +35°C. Less than (5
ppm of setting +0.1 ppm of range +2 uv) per °C from 0°
to +50°C.
STABILITY OF OUTPUT
The following stability specifications apply at the standard
reference conditions noted under ACCURACY OF OUT-
PUT:
Model 341 A:
10V range (whichever is greater)
±0.0007% of setting or 5uv per hour
±0.003% of setting or 15 uv per month
100V range (whichever is greater)
±0.0007% of setting or 10uv per hour
±0.003% of setting or 25 uv per month
1000V range (whichever is greater)
±0.0007% of setting or 20 uv per hour
±0.003% of setting or 50 uv per month
Model 343A:
10V range (whichever is greater)
±0.0005% of setting or 5uv per hour
±0.001 5% of setting or 15uv per month
100V range (whichever is greater)
±0.0005% of setting or 10 uv per hour
±0.0015% of setting or 25 uv per month
1000V range (whichever is greater)
±0.0005% of setting or 20 uv per hour
±0.001 5% of setting or 50 uv per month
OUTPUT CURRENT
0to 25 milliamps at any output voltage.
OVERCURRENT PROTECTION
Automatically limits output current at any present level
between 1and 25 milliamps via continuously variable front
panel control. Panel lamp illuminates during limiting.
SHORT-CIRCUIT PROTECTION
At output voltage dial settings of 299 .99X (299.999X on
the Model 343 A) or less, normal operation is restored upon
removal of overload. At output voltage dial settings of
300.000 (300.0000 on the Model 343A) or above, the
instrument trips to STANDBY when the output is short-
circuited.
RIPPLE AND NOISE (all frequencies)
Model 341A:
60 Hz Line -Less than 100 uv rms or 1mv p-p.
400 Hz Line -Less than 100 uv rms or 2mv p-p.
Model 343A:
60 Hz Line -Less than 50 uv rms or 400 uv p-p.
400 Hz Line -Less than 100 uv rms or 2mv p-p.
SETTLING TIME
Model 341 A: Within 50 ppm of final output in 5 seconds.
Model 343A: Within 25 ppm of final output in 5 seconds.
LINE REGULATION
0.0005% of setting +25 uv for a10% line voltage change
from nominal.
LOAD REGULATION
0.0005% of setting +25 uv for afull load change.
ISOLATION
Either output terminal may be floated up to 500 volts dc
from chassis ground.
REMOTE SENSE
Separate terminals are provided for sensing the output vol-
tage directly at the load, thereby eliminating errors due to
voltage drop in the instrument-to-load connecting wires.
WARM-UP TIME
Model 341A: Within 50 ppm of final output at turn-on.
Within 15ppm of final output in 30 minutes.
Model 343A: Within 25 ppm of final output at turn-on.
Within 5ppm of final output in 30 minutes.
INPUT POWER
115/230 volts ac ±10%, 50 to 440 Hz, single phase.
Approximately 70 volt-amperes fully loaded.
1-0. ENVIRONMENTAL SPECIFICATIONS
TEMPERATURE RANGE
Operating: '0° to +50°C
Storage: -40° to +65°C
Withstands 15 g, 11 millisecond, half sine wave shock per
MIL-T-212G0.
1-2

VIBRATION
Withstands 10 Hz to 55 Hz, 4.5 gmaximum per MIL-
T-21200.
ALTITUDE
Up to 10,000 feet operating and 50,000 feet non-operating,
per MIL-T-21200.
1-7. MECHANICAL SPECIFICATIONS
SIZE
3Hinches high by 17 inches wide by 18 inches deep.
MOUNTING
Mounting brackets provided for standard EIA 19-inch rack
mount, and resilient feet provided for bench use. Tapped
341
A
343A
holes also provided for attaching chassis slides. The instru-
ment outline drawing is shown in Figure 1-1
.
WEIGHT
23 pounds
1-8. GENERAL SPECIFICATIONS
DESIGN
Solid-state throughout
FUSES
Single-fused ac line and high voltage
METER
Monitors output voltage and current
Figure 1-1. MODEL 341A/343A OUTLINE DRAWING
1-3

static
AMessage From
John Fluke Mfg. Co., fnc.
Some semiconductors and custom IC’s can be
damaged by electrostatic discharge during
handling. This notice explains how you can
minimize the chances of destroying such devices
by:
1. Knowing that there is aproblem.
2. Learning the guidelines for handling them.
3. Using the procedures, and packaging and
bench techniques that are recommended.
The Static Sensitive (S.S.) devices are identified in the Fluke technical manual parts list with the symbol
The following practices should be followed to minimize damage to S.S. devices.
2. KEEP PARTS IN ORIGINAL CONTAINERS
4. HANDLE S.S. DEVICES BY THE BODY

L
5. USE ANTI-STATIC CONTAINERS FOR
HANDLING AND TRANSPORT
6. DO NOT SLIDE S.S. DEVICES OVER
ANY SURFACE
7. AVOID PLASTIC, VINYL AND STYROFOAM®
IN WORK AREA
PORTIONS REPRINTED
WITH PERMISSION FROM TEKTRONIX, INC,
AND GENERAL DYNAMICS, POMONA DIV.
®Dow Chemical
8WHEN REMOVING PLUG-IN ASSEMBLIES,
HANDLE ONLY BY NON-CONDUCTIVE
EDGES AND NEVER TOUCH OPEN EDGE
CONNECTOR" EXCEPT AT STATIC-FREE
WORK STATION PLACING SHORTING
STRIPS ON EDGE CONNECTOR USUALLY
PROVIDES COMPLETE PROTECTION TO
INSTALLED SS DEVICES.
9. HANDLE S.S. DEVICES ONLY AT A
STATIC-FREE WORK STATION
10. ONLY ANTI-STATIC TYPE SOLDER-
SUCKERS SHOULD BE USED.
11. ONLY GROUNDED TIP SOLDERING
IRONS SHOULD BE USED.
Anti-static bags, for storing S.S. devices or pcbs
with these devices on them, can be ordered from the
John Fluke Mfg. Co.. Inc.. See section 5in any Fluke
technical manual for ordering instructions. Use the
following part numbers when ordering these special
bags.
John Fluke Part No. Description
453522
453530
453548
454025
Pink Poly Sheet
30"x60“x60 Mil
P/N RC-ASJ 200
$20.00
6" X8” Bag
8" X12” Bag
16” X24” Bag
12” X15” Bag
Wrist Strap
P/N TL6-60
$7.00
J0089B-07U7810/SE EM Litho in U.S..

343A
OPERATING INSTRUCTIONS
2-1. INTRODUCTION
2-2. This section contains operating instructions and
applications infromation for the Model 34 1Aand Model
343AVoltage Calibrators. Unless otherwise specified, all
instructions apply to both instruments.
2-3. If any problem is encountered in operating the
instrument, contact the nearest John Fluke Sales Repre-
sentative or write directly to the John Fluke Manufactur-
ing Company. Please include the instrument serial number
when writing.
2-4. OPERATING FEATURES
2-5 .The following paragraphs describe instrument con-
trols and power requirements.
2-6. CONTROLS, TERMINALS, AND INDICATORS
2-7. The name and function of the front and rear panel
controls, terminals, and indicators are shown in Figure 2-1.
2-8. INPUT POWER REQUIREMENTS
2-9. The instrument operates on either 115 or 230 volt
ac power, and is normally supplied with connections for
11.5 volt use. Dual primary windings in the power trans-
former permit ready conversion from one operating voltage
to the other. The conversion procedure is described in sec-
tion IV, paragraph 4-18.
2-10, PRELIMINARY OPERATION
2-11. The following paragraphs describe preliminary
connections, control settings, adjustments and safety pre-
cautions, which should be observed before operating the
instrument.
2-12, AC LINE CONNECTIONS
2-13. Connect the Model 341 A/343 Aline plug to a
1 1 5volt ac (or to 230 volts ac if the instrument is so
wired), 50 to 440 Hz, single phase, three-wire outlet.
WARNING!
The round pin on the polarized three-prong
plug connects the instrument case to power
system ground. Verify that the ac outlet is pro-
vided with the earth ground wire normally
found in athree wire single-phase connector.
If the third wire is not present in the outlet
or if athree-to-two-wire adapter is used, ensure
that the instrument ground wire is connected
to ahigh quality earth ground.
2-14. SENSE CONNECTIONS
2-15. When aload is connected to the Model 341 A
/
343A, there may be an appreciable voltage drop between
the instrument and the load due to the resistance of the
connecting leads. The nomograph shown in Figure 2-2
can be used to determine the approximate voltage de-
veloped in the leads. If the voltage drop is excessive,
the instrument can then be connected for remote sensing.
2-16. Using The Nomograph. With a straight edge,
connect the point representing output current on scale
1to the point representing the gauge of the connecting
wires on scale 2. The voltage developed in the connecting
wires, expressed in millivolts per foot, is read on. scale 3.
To determine the total voltage developed in the connecting
leads, multiply the total length in feet by the value ob-
tained from scale 3. For example, assume that two AWG
2-1

341
A
343A
Sets the meter mechanical zero. Adjust only after instrument has
been turned off for at least 3minutes.
Selects one of three full-scale voltage ranges: 10, 100 or 1000 volts
dc.
REF. NO. NAME
1Mechanical zero adjust
2RANGE switch
3Power ON indicator
4FUNCTION switch
5LIMIT ON indicator
Illuminates when instrument is fully operable.
Controls instrument input power and output monitoring functions.
In STANDBY/RESET position, all circuitry except the high voltage
power supply is energized. In power ON position, the instrument
is fully operable. When instrument is ON, output voltage is moni-
tored in METER VOLTAGE position and output current in METER
Illuminates when the controlled current limiter is activated. When
lit, output current is limited to apreset value.
Figure 2-1. CONTROLS, TERMINALS AND INDICATORS (Sheet 1of 2)
2-2

341
A
343A
REF. NO. NAME FUNCTION
6CURRENT LIMIT
control
Sets operating point of controlled current limiter, which limits max-
imum output current to any value from zero to about 25 milliamps.
7Ground Terminal Connection for grounding either positive or negative OUTPUT term-
inal to power line ground.
8OUTPUT terminals Output voltage connections, .with both terminal isolated from instru-
ment case and power line ground. Terminals may be floated up to
500 volts dc from chassis.
9SENSE terminals Direct connection to instrument regulating circuitry. Connected to
OUTPUT terminals or remote load to provide optimum load regu-
lation.
10 Decimal lamps Indicate location of decimal point for voltage dial readout, and are
controlled by the RANGE switch.
11 Voltage dials Six voltage dials (seven dials on the 343A) set output voltage and pro-
vide in-line digital readout from 0 to 1 1 11.110 volts dc (0 to 111 1.
1 1 10 volts dc for the Model 343A). Adial set to "X" (10) repre-
sents 0with acarry of 1to the left, thus 11.1 1110 would be dialed
as 10.XXXXX. NOTE: In dial readout notation, the underscore
(10) denotes asingle dial that is displaying two significant digits.
12 Meter Indicates OUTPUT voltage or load current, depending on setting of
FUNCTION switch. The meter voltage range corresponds to the
setting of the RANGE switch. Voltage is indicated on a0to 10
scale, with 10% over-ranging. The meter current range is fixed at 0
to 30 milliamps. NOTE: Meter current includes beta string current.
This introduces asmall error, which is negligible on the 10 and 100
volt ranges; in the 1000 volt range, the error will be equal to +1
milliamp.
13 Terminal strip Provides output, sense, and ground connections for rack-mount in-
stallations. Standard on the Model 343A and option only on the
Model 341 A.
14 Fuse, high voltage High voltage power supply output fuse, rated at 1/16 amp, slow blow.
15 Fuse, line Power line fuse, 1amp slow blow for 115 volts ac operation and 1/2
amp slow blow for 230 volts ac operation.
Figure 2-1. CONTROLS, TERMINALS AND INDICATORS (Sheet 2of 2)
No. 28 wires, each 3ft long, are used to connect aload,
requiring 25 milliamps to the OUTPUT terminals of the
Model 341 A/343 A. With astraight edge, connect the
known current on scale 1(25 ma) and the wire size on
scale 2(No. 28). The resulting IR drop on Scale 3is
approximately 1.65 millivolts per foot. Therefore, the
connecting wires develop atotal voltage of 12 millivolts
(2 x3ft x1.65 mv/ft =9.9 mv), which is more than one
and one-half times the published load regulation of the
instrument at 1000 volts output. To compensate for this.
2-3

OPERATING
CURRENT
MILLIAMPERES
IR DROP m
CONDUCTOR
MV/FOOT
0,02-4-
0.2 --
1
WIRES

341
A
the Mode! 341A/343A is equipped with remote sensing,
which maintains regulation at the load independent of
lead length.
343A
Set the FUNCTION switch to STANDBY/RESET
and remove the short from across the OUTPUT ter-
minals.
2-17. Remote Sensing. If the voltage developed in the
load connecting leads is found to be excessive, proceed as
follows:
a. With the FUNCTION switch set to OFF or to
STANDBY/RESET, remove the front-panel shorting
links between the SENSE and OUTPUT terminals.
b. Using atwisted pair of insulated wires, connect the
+SENSE terminal to the positive side of the load,
and connect the -SENSE terminal to the negative
side of the load.
CAUTION!
Ensure that the SENSE terminals are connected
to the load in the proper polarity. Incorrect
connections will result in loss of regulation and
possible damage to the instrument. When re-
mote sensing is not used, the SENSE terminals
must be connected to the OUTPUT terminals
with the front-panel shorting links.
2-18. CURRENT LIMIT OPERATION
2-19. The CURRENT LIMIT control sets the operating
point of the controlled current limiter, which limits the
instrument output current to any value between 1and 25
milliamps. The approximate value of limiting current is
indicated by a1to 25 scale circumscribed about the
CURRENT LIMIT control on the front panel. If no cur-
rent limiting is desired, set the CURRENT LIMIT control
fully clockwise (25). In this position, maximum instru-
ment output current is available at all voltage settings. If
some degree of current limiting is desired, proceed as fol-
lows:
2-20. OVERLOAD PROTECTION
2-21. The Model 341A/343A is automatically protected
against current overload, and acontinuous short circuit will
in no way harm the unit. At output voltage dial settings of
299.99X (299.999Xon the Model 343A) or less, the output
voltage will return quickly upon removal of the overload.
At voltage dial settings of 300.000 (300.0000 on the Mod-
el 343A) and above, ashort circuit at the output will trip
the instrument to STANDBY. Trip is evidenced by illu-
mination of the CURRENT LIMIT lamp and extinction of
the ON lamp. After the overload condition is corrected,
the instrument may be reset by setting the FUNCTION
switch to the STANDBY/RESET position momentarily
and then back to ON.
2-22. Output voltages are fully controlled when down-
ranging or switching to STANDBY. This is accomplished
by apair of crowbar relays, which discharge the high vol-
tage filter capacitors in aseries of steps. The action of the
crowbar relays is very rapid and is audible to the user.
When downranging from the 1000 volt range (500 to
1000 volt dial settings) to the 100 or 10 volt ranges, crow-
bar operation can be heard as arattle as the switch position
is changed. The crowbar circuit provides continuous pro-
tection as long as downranging is not excessive; however,
if downranging occurs consistently at intervals less than
5seconds, the instrument will automatically trip to
STANDBY.
2-23. MECHANICAL ZERO ADJUSTMENT
2-24. When necessary, mechanically zero the meter with
the adjustment screw on the front panel. If the instrument
has been operating, it must be turned off for at least 3
minutes prior to this adjustment.
a. Set the Model 341A/343A control as follows: 2-25. OPERATION AS AVOL IAGE CALI-
BRATOR
FUNCTION
RANGE
Voltage dials
CURRENT LIMIT
STANDBY/RESET
10
1.00000 (Model 341 A)
1.000000 (Model 343A)
Fully clockwise
b. Place ashort across the +and -OUTPUT terminals.
2-26. To use the Model 341A/343A as a voltage source,
proceed as follows:
a. Set the FUNCTION switch to STANDBY/RESET.
Allow at least a10-minute warm-up period if the
instrument has just been energized.
c. Set the FUNCTION switch to METER CURRENT.
d. Set the output current limit by rotating the CUR-
RENT LIMIT control counterclockwise until the
panel meter indicates the desired limiting current.
Connect the SENSE terminals to the OUTPUT ter-
minals with the shorting links provided and. connect
the load. If remote sensing is desired, connect the
SENSE terminals to the load as described in para-
graph 2-17.
2-5

341
A
343A
c. Set the CURRENT LIMIT control fully clockwise
(25) or to a predetermined value, using the proce-
dure of paragraph 2-17.
d. Set the RANGE switch and voltage dials to the value
of the desired output voltage.
e. Set the FUNCTION switch to ON.
f. The output voltage delivered to the load will corres-
pond to the voltage indicated on the voltage dials.
To monitor output voltage or current, place the
FUNCTION switch in either the METER VOLTAGE
or METER CURRENT position.
2-27. APPLICATIONS
2-28. The Model 341 A/343AVoltage Calibrators pro-
vide parameters of stability, accuracy, temperature co-
efficient and response required by abroad range of labora-
tory and production applications. The following para-
graphs describe amethod of using the instrument as a
differential voltmeter and, in conjunction with areference
divider, as aprecision voltage source with traceability to
the National Bureau of Standards.
2-29. OPERATION AS ADIFFERENTIAL
VOLTMETER
2-30. The Model 341 A/343Acan be used in combina-
tion with anull detector, such as the Fluke Model 845AB,
as adifferential voltmeter. Connection of the equipment
for measurement of apositive voltage is shown in Figure
2-3. Proceed as follows:
MODEL 34 1A/343A
Figure 2-3. DIFFERENTIAL VOLTMETER
a. Connect the null detector INPUT terminal to the
positive terminal of the voltage to be measured, and
connect the null detector COMMON terminal to the
Model 341 A/343A+OUTPUT terminal. Connect
the Model 341A/343A -OUTPUT terminal to the
negative side of the voltage being measured.
WARNING!
To eliminate shock hazard, leave the ground
terminals of the Model 341 A/343Aand null
detector disconnected.
b. Set the null detector voltage range and Model 341 A/
343A voltage dials to approximately the voltage being
measured. If the voltage being measured is not
known, set the null detector to the 1000 volt range
initially.
c. Set the Mode] 341 A/343AFUNCTION switch to ON,
and set the CURRENT LIMIT control as desired.
d. Set the Model 341 A/343ARANGE switch and vol-
tage dials to the approximate voltage indicated by.
the null detector. The null detector should then
indicate anull.
e. Set the null detector for increased sensitivity, and
adjust the voltage dials for zero deflection on the
null detector.
f. The value of the voltage being measured is indicated
by the Model 341 A/343Avoltage dial setting at zero
deflection of the null detector.
g. To measure anegative voltage, reverse the connec-
tions at the Model 341 A/343AOUTPUT terminals.
2-3 1.OPERATION AS A 10PPM SOURCE
2-32. The Model 341 A/343Atogether with areference
divider such as the Fluke Model 750A can provide voltages
of 0.1, 0.5, 1, 1.1, 5, 10, 50, 100, 500, 1000, and 1100
volts dc, which have an accuracy of 10 ppm and are trace-
able to the National Bureau of Standards. Equipment
connection is shown in Figure 2-4. Proceed as follows:
a. Set the Model 750A input switch to RESET Adjust
the Model 341 A/343ACURRENT LIMIT control
for 2milliamps, using the procedure of paragraph
2-18.
b. Set the Model 341 A/343 AFUNCTION switch to
STANDBY/RESET. Set the Model 750A standard
cell voltage dials to the voltage of the standard cell.
2-6

341
A
343A
MODEL MODEL
750A341 A/343
A
SIMPLIFIED
MODEL 750A
Figure 2-4. OPERATION AS A10 PPM SOURCE
c. Set the input voltage switch of the Model 750A as
desired. Set the Model 341A/343A output to the
same voltage.
d. Set the Model 341 A/343AFUNCTION switch to ON
and set the Model 845 AB for 100 microvolts sensi-
tivity.
e. Adjust the voltage dials of the Model 341A/343A
and the coarse and fine dials of the Model 750A for
anull on successively more sensitive null ranges of
the Model 845 AB. Final null should be on the 10
microvolt range.
f. The output voltage of the Model 750A corresponds
to the output voltage switch setting.
2-7