38 Keysight 8478B Thermistor Mount
Maintenance
Thermistor Compensation
4-
Thermistor Compensation
If the resistance reading is satisfactory, it may be possible to re-compensate
the mount, and return it to service. The drift with temperature changes will be
higher because of the damage to the thermistors, but it will be possible to zero
the meter and to make accurate measurements. The Effective Efficiency and
Calibration Factor imprinted on the label will no longer be valid (refer to
). There are two adjusting screws which permit
re-compensation within limits.
Figure 4-4
Printed Circuit Board
Refer to
and proceed as follows:
1. Remove the three screws (A).
2. Slide terminal shield away from instrument.
3. Plug connector J2 into Model 432A.
4. Connect mount to 50
Ω
load.
5. Set:
If meter is pegged downscale:
1. Set RANGE to COARSE ZERO.
2. Set COARSE ZERO and adjustment to mid range.
MOUNT RES:
200
Ω
POWER:
ON
