Keysight 1143A, User'S And Service Manual

Page: 31 / 56

To adjust offset zero
This procedure adjusts the probe offset drive current to zero when the offset
is turned off.
Equipment Required
Equipment Critical Specification Recommended
Model/Part
Digital Multimeter Better than 0.1% accuracy 3458A
Resistor 511
Ω
, 0.5 W, 1% 0757-0814
Use the adjustment locator on page 28 to find the test points and adjustments.
Do not make this adjustment while using a probe as a load on the offset
circuit. It will give the wrong result.
1
Set the front-panel Probe 1 and Probe 2 offset controls for Zero and
Local.
2
Connect the DVM between TP5 (ground) and TP3 (Probe 1 Offset).
3
Connect the 511-
Ω
resistor between TP5 and TP3.
4 Adjust R9 (Probe 1 Offset Zero) for a reading of 0.0V
±
100
µ
V.
5
Connect the DVM between TP5 (ground) and TP4 (Probe 2 Offset).
6
Disconnect the 511-
Ω
resistor from TP3 and connect it to TP4
(between TP5 and TP4).
7 Adjust R27 (Probe 2 Offset Zero) for a reading of 0.0V
±
100
µ
V.
If the offset zero cannot be adjusted into tolerance, go to the "Troubleshooting
and Repair" section of this chapter.
Service
Making Adjustments
31