TB 9-6625-133-40
(8) Press nullmeter INPUT OFFSET knob as necessary to select "V".
(9) Rotate INPUT OFFSET knob until nullmeter indicates "0".
(10) Zero other nullmeter ranges as desired (see note above).
(11) Up-range nullmeter.
(12) Remove the short from the NULL DETECTOR terminals and move it to the
INPUT terminals of the reference divider. Do not disconnect or change the settings on the
calibrator.
(13) Press nullmeter INPUT OFFSET knob as necessary to select "I".
(14) Down range nullmeter and rotate INPUT OFFSET knob to maintain a
nullmeter "0" indication. Final adjustment should be made on the 3 uV range.
(15) Switch DC voltage divider between +100:1 and -100:1, adjusting nullmeter
INPUT OFFSET knob for best compromise between the two settings.
(16) Press nullmeter INPUT OFFSET knob as necessary to select the padlock.
(17) Up range nullmeter and set calibrator output to STBY.
(18) Remove the short from the INPUT terminals of the DC voltage divider. Do not
disconnect or change the settings on the calibrator.
g. Self calibrate the reference divider by performing (1) through (18) below.
(1) Ensure that the reference divider has been in a thermally stable environment
for at least 4 hours.
(2) Ensure that equipment is connected as shown in figure A-1 connection A.
(3) Ensure that the reference divider MODE switch is set to 752 CAL.
(4) Set the reference divider CALIBRATE switch to 10:1+.
(5) Set the calibrator output to 20 VDC, output to OPR.
(6) Set the nullmeter to the lowest range that allows an on-scale reading.
(7) Allow time for indication to stabilize then note the reading on the nullmeter.
(8) Set the reference divider CALIBRATE switch to 10:1-.
(9) Allow time for indication to stabilize then note the reading on the nullmeter. If
there is a difference between the switch positions, adjust the BALANCE control such that
the nullmeter readings are the same in both the "+" and "-" switch positions.
(10) If the nullmeter reading is not "0" after adjusting the BALANCE control, adjust
the 10:1 control for "0".
(11) Continue down-ranging the nullmeter while adjusting the BALANCE control
and the 10:1 control until the nullmeter indication is "0" 0.5 uV when switching between
10:1+.and 10:1- switch positions.
(12 Up range nullmeter.
(13) Set the reference divider CALIBRATE switch to 100:1+.
(14) Set the nullmeter to the lowest range that allows an on-scale reading.
A-5