4 Calibration Procedures
76 Keysight 34970A/34972A Service Guide
Test Considerations
To ensure proper instrument operation, verify that you have selected the correct
power line voltage prior to attempting any procedure in this chapter. See “If the
Instrument Does Not Turn On” on page 41.
Errors may be induced by AC signals present on the input leads during a self-test.
Long test leads can also act as an antenna causing pick-up of AC signals.
For optimum performance, all procedures should comply with the following
recommendations:
– Assure that the calibration ambient temperature is stable and between 18 °C
and 28 °C. Ideally the calibration should be performed at 23 °C ±1 °C.
– Assure ambient relative humidity is less than 80%.
– Allow a 2-hour warm-up period with a copper short connected and the
multiplexer module installed before verification or adjustment.The connections
are shown in the figure on page 69.
– Use shielded twisted pair PTFE insulated cables to reduce settling and noise
errors. Keep the input cables as short as possible.
– Connect the input cable shield to the source LO output.Except where noted in
the procedures, connect the calibrator LO source to earth ground.
Two-wire Ohms measurements are affected by the entire path length, including
the plug-in card trace length and slot trace lengths. On the 34901A, Channel 10 is
recommended as the median path length (on the 34902A, use Channel 8) for
2-wire Ohms verification and adjustments. Install the input multiplexer in slot 200.
Because the instrument is capable of making highly accurate measurements, you
must take special care to ensure that the calibration standards and test
procedures used do not introduce additional errors. Ideally, the standards used to
verify and adjust the instrument should be an order of magnitude more accurate
than each instrument range full scale error specification.
For the DC voltage, DC current, and resistance gain verification measurements,
you should take care to ensure the calibrator’s “0” output is correct. If necessary,
the measurements can be referenced to the calibrator’s “0” output using Mx + B
scaling (see page 57). You will need to set the offset for each range of the
measuring function being verified.
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