Fluke 5220A, Instruction Manual

Page: 59 / 138

Maintenance
Calibration Adjustments
4
4-13
4-30. Initial Conditions
Before starting the following procedures, condition the 5220A as follows:
1. Disconnect all input and remote connections to the 5220A, and connect a short
jumper wire between the selected output terminals.
2. Connect the unit to line power and set the POWER switch to ON. Only the STDBY
and FRONT LEDs should light.
3. Set the 5220A to the operate mode and allow it to warmup for at least 30 minutes.
4. Remove the top and large inner cover from the unit, and complete the following
procedures.
4-31. Input Offset Adjustment
The following procedure is used to adjust input offset (R6) on the A5 Preamplifier PCB
Assembly:
1. Connect the load resistor (0.1 ohm) to the enabled (front/rear) 5220A output
terminals.
2. Connect the DVM to the sense terminals on the load resistor and select the 100 mV
dc range.
3. Connect a short jumper wire between the front VOLTAGE INPUT terminals.
4. Set the 5220A to the operate mode.
5. Adjust R6 on the A5 Preamplifier PCB Assembly for a DVM reading of -.010 to -
.010 mV dc (0 +10
µ
V dc).
6. Set the 5220A to the standby mode.
4-32. Driver Offset Adjustment
The following procedure is used to adjust input offset (R6) on the A6 Driver PCB
Assembly. The procedure is accomplished with the 5220A in the standby mode:
1. Jumper test lead between TP7 (-15 V dc) on the A4 Regulator and TP4 (Turn on 1)
on the A8 Analog Control. This enables the A8 Analog Control and A7 Output while
the A5 Preamplifier is clamped to zero (standby).
2. Adjust R6 on the A6 Driver for a DVM reading of -1.000 to +1.000 mV dc.
3. Disconnect the test lead from TP4 and TP7.
4. Remove the load resistor from the 5220A output terminals.
5. Remove the jumper wire from the front-panel VOLTAGE INPUT terminals.