Fluke 742A-10k User manual

P/N 850255
September 1988
©1988, John Fluke Mfg. Co., Inc., all rights reserved. Litho in U.SA

WARRANTY
John Fluke Mfg. Co., inc. (Fluke) warrants this instrument to be free from defects in material and workmanship
under normal use and service for aperiod of 1year from date of shipment. Software is warranted to operate in
accordance with its programmed instructions on appropriate Fluke instruments, it is not warranted to be error
free. This warranty extends only to the original purchaser and shall not apply to fuses, computer media,
batteries or any instrument which, in Fluke’s sole opinion, has been subject to misuse, alteration, abuse or
abnormal conditions of operation or handling.
Fluke’s obligation under this warranty is limited to repair or replacement of an instrument which is returned to
an authorized service center within the warranty period and is determined, upon examination by Fluke, to be
defective. If Fluke determines that the defect or malfunction has been caused by misuse, alteration, abuse, or
abnormal conditions of operation or handling, Fluke will repair the instrument and bill the purchaser for the
reasonable cost of repair. If the instrument is not covered by this warranty, Fluke will, if requested by
purchaser, submit an estimate of the repair costs before work is started.
To obtain repair service under this warranty purchaser must forward the instrument, (transportation prepaid)
and adescription of the malfunction to the nearest Fluke Service Center. The instrument shall be repaired at
the Service Center or at the factory, at Fluke’s option, and returned to purchaser, transportation prepaid.
FLUKE ASSUMES NO RISK FOR IN-TRANSIT DAMAGE.
THE FOREGOING WARRANTY IS PURCHASER’S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED
WARRANTY OF MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE OR USE. FLUKE
SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR
LOSS WHETHER IN CONTRACT, TORT, OR OTHERWISE.
M
Immediately upon arrival, purchaser shall check the packing container against the enclosed packing list and
shall, within thirty (30) days of arrival, give Fluke notice of shortages or any nonconformity with the terms of the
order, If purchaser fails to give notice, the delivery shall be deemed to conform with the terms of the order.
The purchaser assumes all risk of loss or damage to instruments upon delivery by Fluke to the carrier. If an
instrument is damaged in transit, PURCHASER MUST FILE ALL CLAIMS FOR DAMAGE WITH THE CARRIER
to obtain compensation. Upon request by purchaser, Fluke will submit an estimate of the cost to repair
shipment damage.
Fluke will be happy to answer ali questions to enhance the use of this instrument. Please address your
requests or correspondence to: JOHN FLUKE MFG. CO., INC., P.O. BOX C9090, EVERETT, WA 98206,

INTRODUCTION
The 742ASeries are small, light, rugged resistance standards. The standards require no
temperature-controlled air or oil bath. The 742A Series are well suited for use as the
following:
•Working standards
•Portable transfer standards
•Calibration support for the Fluke 5700A Calibrator
Stability and temperature coefficients of the 742A Series make them ideal for easy trans-
port to and operation in any working environment within the range of 18 to 28° C. The
standards come with six-month and one-year uncertainty specifications. Depending on
the accuracy required, a742A can be recertified at intervals based on either specification.
Each 742Acomes with aReport of Calibration and arear panel label showing the mea-
sured value. The rear panel also has a Fluke Primary Standards Lab calibration label,
labels that show temperature coefficient alpha and beta centered on 23° C, and the stan-
dard’s serial number.
NOTE
Refer to “How Temperature Correction Factors are Calculated, ”
further on in this manualfor definitions of alpha and beta.

SPECIFICATIONS
Table 1lists specifications for the available 742A Series Resistance Standards.
ODEL NOMIN
RESiSTA
AT 23° C
742A-1 IQ ±5.0 ppm +8.0 ppm ±1.0 ppm 3.0 ppm 500 mA
(500 mV)
742A-10k 10 kQ ±2.5 ppm ±4.0 ppm ±1.0 ppm 1.5 ppm 3mA (30V) 0.6 mA
GENERAL SPECIFICATIONS:
Accuracy: The initial resistance is trimmed to +2 ppm of nominal. The measured value is
printed on the rear panel.
Operating Temperature Range: 23 ±5°C
Storage Temperature Range: 0to 40° C
Report of Calibration: The report of calibration includes atable of resistance values in 0.5° increments
from 18 to 28° C.
Size: 8.64 cm Hx10.54 cm Wx12.70 cm L(including binding posts)
(3.4 in Hx4.15 in Wx5.0 in L(including binding posts))
Binding posts: 2.54 cm (1.0 in)
Weight: 0.91 kg (2.0 lbs)

DESIGN AND CONSTRUCTION NOTES
The 742A Series are constructed of arrays of Fluke wirewound precision hermetically-
sealed resistors. No adjustable resistors of any kind are used.
Each 742Ais built with atemperature coefficient near zero at 23° C. To further reduce
errors caused by temperature changes, the binding posts are constructed of low-thermal
emf material.
FEATURES
Figure 1shows afront panel view. Figure 2shows arear panel view. Table 2describes
binding post functions. Table 3describes the rear panel labels.
Figure 1. Typical Front Panel View
Table 2. Functions of the Binding Posts
742A BINDING POST FUNCTION
CURRENT HI Input for the current source from an ohmmeter
CURRENT LO Input for the current source from an ohmmeter
SENSE HI Measurement point for afour-wire ohmmeter
SENSE LO Measurement point for afour-wire ohmmeter
CHASSIS GROUND Connected to the case for shielding

MEASURED VALUE
TEMPERATURE COEFFICIENTS (AT 23°C)
ALPHA —-0.09 E-6
BETA --0,039 E-6
PRIMARY STANDARDS LABORATORY
CERTjF)ED—
fluke JOHN FLUKE MFG CO., INC.
IWtVMt
Measured value label. Shows the measured value at 23±0.6°; the same as on the Report of
Calibration.
Temperature coefficient label. Shows alpha and beta centered on 23° C. Refer to “How
Temperature Correction Factors are Calculated,” further on in this manual for definitions of
alpha and beta, and the formula to predict exact resistance at different temperatures.
Fluke Primary Standards Lab Calibration Label documents traceability to the U.S. National
Bureau of Standards.
Serial number label. Shows the standard's serial number. This number and the full model
number (i.e., 742A-1) positively identify aparticular unit.

OPERATING NOTES
This part of the manual explains operational and environmental considerations for the
742A Series. Follow these guidelines when operating or storing the resistance standard.
Precautions for handling are under “Care and Maintenance.”
Connecting to the 742A Series
CAUTION
Do not apply voltages above the maximum voltage printed on the
front panel. Excessive voltage can cause apermanent shift in resis-
tance value or damage.
The specifications for models with CURRENT and SENSE binding posts require four-
wire connections to the standard. Use these binding posts as described in Table 2.
For the case to act as ashield, the CHASSIS GROUND binding post must be connected
to earth ground or instrument guard at some point in acalibration system. Normally
when two or more instruments with guards are connected together, the use of asingle
common grounding point avoids ground loops. If applicable, ground the 742A CHAS-
SIS GROUND binding post to that common grounding point.
Figure 3shows atypical connection to afour-wire ohmmeter. Figure 4shows the connec-
tion used to calibrate the 10 internal resistance standard in the 5700A.
Cable Recommendations
For optimum results, use two sets of the Fluke 5440A-7004 Low Thermal Test Leads,
which are designed to reduce errors caused by thermal emfs.

Figure 4. Connection to Calibrate the 5790A
You can use the 742A Series in ambient temperatures between 18 and 28° C. To predict
the deviation from nominal at temperatures other than 23° C, use the temperature char-
acterization table provided with each unit. The table shows the calculated value and the
deviation from nominal at temperatures between 18 and 28° Cin half-degree increments.
An example of this table is included as Table 4.
Alabel on the rear panel shows temperature coefficient factors alpha and beta centered
on 23° C. (See Figure 2for the label location.) The values of alpha and beta are individual-
ized for each 742A. Alpha and beta are established by measurement in the Fluke Primary
Standards Lab at 18°C, 23° C, and 28° C. The temperature characterization table is
generated from these three measurements and the following formula:
R, =R23 [1 +a(t-23) +P(t-23)2J
Where, Rt=Resistance at t°C
R23 =Resistance at 23°C
a=Slope of the curve (ppm/°C) at 23°C
p=Rate of change of slope of the cun/e (ppm/°C 2)
aand pare constants which do not change appreciably over
time and hence need to be determined only once.
In the case of the example 742A-1 used in this manual, aand p
are calculated as follows:
a(R28-Ris)
At
-0.9 E-6
to'"
-"" -0.09 E-6
P
Where,
(R28 +Ris
)
2
f.) 2
2>
R23 -0.85 E-6
25 -0.034 E-6
R2s =Resistance at 28°C
Ris =Resistance at 18°C
R23 =Resistance at 23°C
At =(28- 18) =10

Test
Date:
Page
Number: XXXX
04-Aug~88
2of 2
Serial No,: XXXXXX
Alpha --0.090 E-6
Beta =-0.034 E-6
Temp
(Celsius
)
Resistance
(OHMS }
Dev from nominal
(in ppm)
18.0 1.0000006 0.6
18.5 1.0000007 0.7
19.0 1.0000008 0.8
19.5 1.0000009 0.9
20.0 1,0000010 1.0
20.5 1.0000010 1.0
21,0 1.0000010 1.0
21.5 1,0000011 1.1
22.0 1.0000011 1.1
22.5 1.0000010 1.0
23.0 1.0000010 1.0
23.5 1.0000009 0.9
24.0 1.0000009 0.9
24.5 1,0000008 0.8
25.0 1.0000007 0.7
25,5 1.0000006 0.6
26.0 1.0000004 0.4
26.5 1.0000003 0.3
27.0 1.0000001 0.1
27.5 0.9999999 -0.1
28.0 0.9999997 -0.3

Figure 5shows agraph of the value of the 742A-l represented by the sample tempera-
ture characterization chart (Table 4). To illustrate use of the formula, calculations for
resistance at 20° Cand 26° Care shown. You can see that using the formula shown with
alpha and beta you get the same value as in the characterization table.
TEMP °C
figure 5. Graph of Resistance VS. Temperature for Sample 742A-1
Rt *R23 (1+a(t-23) +P(i-23)2]
At ss 20°C
R20 *1.0000010 [1+{-0.09 E-6) (-3) +{-0.034 E-6) {-3)2J
=1.0000010 {1.0000003- 0.0000003)
=1.0000010 {1.0000000 )
=i.oooooi on
R{=R23 [1+a{t-23 )+p(t -23 )2]
At =26°C,
R26 =1.0000010 [1+(-0.09 E-6) (3) +{-0.034 E-6) (3)2]
=1.000001 0(1 -0.0000003 -0.0000003 )
=1.0000010 (1 -0.0000006)
=1.0000004Q
Storage Temperature Range
To maintain accuracy within the specified limits, do not subject the 742A Series to
temperatures below 0° Cor above 40° C. If exposure to temperatures outside this range is
unavoidable, you can minimize the adverse effects by doing the following:
•Keep the standards in the optional transit case (Option 742A-7002). The transit case
is insulated and helps protect the standards during short-term temperature extremes.
Keep exposure to temperature extremes brief.