Fluke 540B - Preliminary Transfer Calibration Check

4-18. SENSITIVITY TEST CALTBRATION. Calibration
of the SENSITIVITY TEST circuit requires a de voltage
source with an accuracy of ±0. 003%. Refer to Figure
5-2 for adjustment locations. Remove the bottom cover
of the Model 540B and proceed as follows:
a. GALV switch OPEN
RANGE switch. 5
MODE
switch DC SEARCH
SENSITIVITY
switch LOW
b. Connect
0. 50055 volts de to the DC INPUT terminals.
c. Set all REFERENCE ADJUST controls to the center
of their ranges.
d. MODE switch DC TRAN SFER
GALV switch LOCK
e. Adjust COARSE and MEDIUM contro ls for zero
reading on the GALVANOMETER.
f. GALV
switch OPEN
SENSITIVITY
switch HIGH
g. Adjust GALV ZERO for zero reading on the GAL-
VANOMETER.
h. GAL V
switch to LOCK.
i. Adjust MEDIUM and FINE controls for zero reading
on the GALVANOMETER.
j. Adjust external voltage source for 0. 50005 volts de
at the DC INPUT terminals.
k. SENSITIVITY TEST switch to 0. 1%.
1. Adjust R402 for zero ±5 minor divisions GALVANo-
METER deflection.
m. Set SENSITIVITY TEST switch to OPR, and adjust
external voltage source for 0. 50055 volts de.
n. GALV
switch to OPEN.
o. Adjust GALV ZERO
for zero reading on the GAL-
VANOMETER.
p. GALV switch to LOCK.
q. Adjust MEDIUM and FINE controls for zero reading
on
the GALVANOMETER.
r .
Adjust external voltage source for 0. 50050 volts
de at the DC INPUT terminals.
s. SENSITIVITY TEST switch to 0. 01% .
t. Adjust R401 for zero ±0. 5 minor divisions GAL-
VANOMETER deflection.
u. SENSITIVITY TEST switch OPR
GALV switch OPEN
v. Disconnect
test equipment and replace bottom cover
on Model 540B.
540B
4-19. PRELIMINARY TRA N SFER CA LI BRA TI O N
CHECK
4- 20. GENERAL
4-21. Any method of checking
the Model 540B transfer
calibration consists of checking it against a standard
of known accuracy. Laboratory transfer equipment,
whose accuracy equals or exceeds the specifications of
the Model 540B, with a current test report from NBS
traceable standards may be used. A Model 540B with
a
recently issued test report may be used to check a-
nother Model 540B over its entire range. In addition to
a known standard of comparison, it will also be neces-
sary to have a complete set of equipment as outlined in
Figure 2-3.
4-22. The Model 540B under test must pass all of the
isolation tests (3) and the reversal tests, before a valid
check may
be made of trans f er calibration. It is neces-
sary to note that should the Model 540B fail to pass the
calibration check of the . 5 volt range, it is reasonable
to assume that all of the ranges are out of calibration.
The basic compensation is made in the • 5 volt range
and all ranges are dependent upon t his compensation.
Should the • 5 volt range be within the limits of cali-
bration it is reasonable to proceed with the calibration
checks of tJle other ranges. No other range will so effect
the calibration of any other range, as each range is
compensated dependent on the . 5 volt compensation and
its own compensating elements.
4-23. If a range is found to be out of specified limits
and it is not feasible to send the instrument back to the
factory for recalibration, it may be checked at each
frequency and voltage to be used and a correction chart
made to calculate the deviations. Should the reversal
error or heater to couple isolation tests fail to meet
specifications it will be necessary to replace the ther-
mocouple and the instrument should be recalibrated.
4-24 . REVERSAL ERROR
4-25. Check in accordance with Section 2-15.
4-26 : HEATER TO COUPLE ISOLATION
4-27. The purpose of this test is to insure the adequate
isolation between the heater and the couple element of
the thermocouple. Proceed as follows:
a. POWER switch OFF .
MODE
switch DC TRANSFER.
GALV
switch OPEN.
HIGH
FREQ CONVERTER plug remo v ed.
b. Measure the resistance between pin 1 or pin 2 of
the HIGH FREQ CONVERTER jack and the negative
DC INPUT (lower) binding post. This resistance
must be 10 megohms or higher. Restore the HIGH
FREQ CONVERTER plug and turn the MODE switch
to OFF .
4-28. GALVANOMETER GROUND ISOLATION
4-29. The purpose of this test is to verify the isolation
of the galvanometer
circuit from chassis ground. Pro-
4-5