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Input bias current and offset voltage calibration
The input bias current and offset voltage calibration procedures that follow should be per-
formed periodically to actively cancel input bias current and offset voltage, optimizing measure-
ment accuracy, particularly at low levels.
Front panel
Front panel input bias current calibration
1.
NOTE
2.
3.
4.
5.
6.
Front panel offset voltage calibration
1.
2.
3.
4.
5.
6.
Access the front panel calibration menu by pressing SHIFT then CAL.
See Section 19 for details on other calibration menu selections.
From the calibration menu, use the down RANGE key to display the following:
CAL: IOFFSET
Press ENTER. The instrument will prompt for the triax shielding cap as follows:
INPUT CAP
Connect a triax shielding cap to the rear panel INPUT jack. (Use a Keithley CAP-31 or
equivalent.)
Press ENTER to complete input bias current calibration.
If you wish to perform front panel offset voltage calibration, proceed to Step 2 of the pro-
cedure below. Otherwise, press EXIT to return to normal display.
Access the front panel calibration menu by pressing SHIFT then CAL.
From the calibration menu, use the up or down RANGE key to display the following:
CAL: VOFFSET
Press ENTER. The instrument will prompt for a short:
INPUT SHORT
Connect a triax short to the rear panel INPUT jack. (Use the supplied Model 237-ALG-
2 triax cable or equivalent with red and black alligator clips connected together.)
Press ENTER to complete offset voltage calibration.
Press EXIT to return to normal display.
Measurement Concepts
2-17
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