4 Calibration Procedures88 Keysight 34970A/34972A Service GuideInternal DMM AdjustmentsYou will need a 34901A 20-Channel Multiplexer to perform the followingprocedures (see page 69). Install the Multiplexer in slot 200.Zero AdjustmentEach time you perform a zero adjustment, the Internal DMM stores a new set ofoffset correction constants for every measurement function and range. TheInternal DMM will sequence through all required functions and rangesautomatically and store new zero offset calibration constants. All offsetcorrections are determined automatically. You may not correct a single range orfunction without re-entering ALL zero offset correction constants automatically.This feature is intended to save calibration time and improve zero calibrationconsistency.Zero Adjustment ProcedureThe zero adjustment procedure takes about 5 minutes to complete. Be sure toallow the instrument to warm up for 2 hours before performing the adjustments.Follow the steps outlined below. Review “Test Considerations” on page 76 beforebeginning this test. Also see page 56, for an example of how to initiate a zerocalibration.1 This procedure will use the copper shorts installed on Channels 209 and 219.Leave the Amps input connections (Channel 221) open.2 Select Channel 209. Select the DC VOLTS function.3 Press to enter the calibration menu. Press again to begin theadjustment procedure.4 Use the knob and arrow keys to set the number in the display to 0.000000 andpress .5 Perform the Zero Offset Verification tests (see page 80) to check zerocalibration results.NOTE Never turn off the Internal DMM during Zero Adjustment.This may cause ALLcalibration memory to be lost.
