Section Iii Preliminary Operations; Preliminary Instructions; Equipment Setup - HP 431B Calibration Procedure

TB 9-6625-086-35

6. Preliminary Instructions

a. The instructions outlined in this section are preparatory to the calibration process.
Personnel should become familiar with the entire bulletin before beginning the calibration.
b. Items of equipment used in this procedure are referenced within the text by common
name and item identification number as listed in tables 2 and 3. For the identification of
equipment referenced by item numbers prefixed with A, see table 2, and for prefix B, see
table 3.
HIGH VOLTAGE is used during the performance of this
calibration. DEATH ON CONTACT may result if personnel
fail to observe safety precautions.

7. Equipment Setup

a. Connect autotransformer (A1) to the power source and adjust for 115 volts ac.
Throughout this procedure, make sure the TI is deenergized
while connecting or disconnecting a thermistor mount or when
repositioning the MOUNT RES switch.
b. Connect the TI to autotransformer.
c. Adjust the TI mechanical zero setscrew clockwise until the pointer is left of zero,
moving up scale. Stop when the pointer indicates zero.
If pointer overshoots zero indication during adjustment, repeat
c above.
d. Adjust the zero setscrew approximately 15 degrees counterclockwise to free the
setscrew from the meter movement.
e. If the pointer moves while freeing the setscrew, repeat c and d above.
f. Connect 200-ohm thermistor mount (A8) to the TI, using cable furnished with the TI
and terminate the mount with coaxial termination (B6).
g. On model 431C, set the CALIB FACTOR PERCENT switch to 100 and leave it in
this position for the remainder of the procedure.
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SECTION III
PRELIMINARY OPERATIONS
WARNING
CAUTION
NOTE