5 Verification and Performance Tests
Test Considerations
140 U3606A User’s and Service Guide
Test Considerations
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 (T
cal
) is stable and
between 18 °C and 28 °C. Ideally the calibration should be performed
at 23 °C ± 2 °C.
• Assure that the ambient relative humidity is less than 80%.
• Allow a 60- minute
[1]
warm- up period with a shorting plug connected to
the V (red) and LO (black) input terminals.
• Use shielded twisted- pair of Teflon- insulated cables to reduce settling
and noise errors. Keep the input cables as short as possible.
• Connect the input cable shields to earth ground. Except where noted in
the procedures, connect the calibrator
LO source to earth ground at the
calibrator. It is important that the
LO to earth ground connection be
made at only one place in the circuit to avoid ground loops.
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 of full
scale error specification.
For the DC voltage, DC current, and resistance gain verification
measurements, you should take careful measures to ensure that the
calibrator “0” output is correct. You will need to set the offset for each
range of the measuring function being verified.
[1] 120-minute warm-up period for instrument adjustments (calibration). See Chapter 6, “Calibration
Procedures,” starting on page 171 for more information on the calibration procedures.
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