TB 9-6625-133-40
(15) Allow time for indication to stabilize then adjust the 100:1 control, if necessary,
for "0" on the nullmeter
(16) Continue down-ranging the nullmeter and adjusting the 100:1 control until the
nullmeter indicates "0" 1 uV in both 100:1+ and 100 positions. Do not use the
BALANCE control.
(17) Up range nullmeter and set calibrator output to STBY.
(18) Set the reference divider CALIBRATE switch to OPERATE.
h. Characterize the calibrator DC voltage output by performing (1) through (25) below.
(1) Connect equipment as shown in figure A-1, connection A and B. Remove line
power from nullmeter and transfer standard. All measurements should be made using
battery power.
(2) Set reference divider MODE to 10V. Ensure that reference divider CALIBRATE
switch is set to OPERATE.
(3) Lock calibrator on the 22 V dc range.
(4) Set calibrator output to the same value as the test reported value of the transfer
standard 10 V tap (i.e., 10.000072), output to OPR.
(5) Down range nullmeter while using calibrator rotary knob to obtain finest null on
lowest possible nullmeter range that was zeroed (i.e., 3 uV range).
(6) Record the value of the calibrator output display (i.e., 10.000074 V) in the
"calibrator display" column in table A-2, row 5.
(7) Record the value on the calibrator error display as ERROR ppm (i.e., -0.2 ppm)
for use in (9) below.
(8) Up range nullmeter and set calibrator output to STBY.
(9) Apply the ERROR ppm recorded in (7) above to the 19.000000 V dc output using
ERROR ppm
ACTUAL = NOMINAL -
the formula below.
,
,
Where:
ACTUAL= Calibrator displayed output.
NOMINAL = 19.000000 (True applied voltage)
ERROR ppm = Value on the calibrator error display
(10) Record the value calculated in (9) above in the Calibrator Display column in
table A-2, row 7.
(11) Set calibrator range to AUTO.
(12) Set reference divider MODE to 100V/10:1.
(13) Set calibrator output to 10 times the test reported value of the transfer standard
10 V tap (i.e., 100.00072 V), output to OPR.
A-6