Performance Tests and Calibration
4
34405A User’s and Service Guide
67
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 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 1- hour warm- up period with a Shorting Plug connected to the
HI and LO input terminals.
•
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 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 very 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.
Input Connections
Test connections to the instrument are best accomplished using the dual
banana plug with copper wire short between two terminals for
low- thermal offset measurement. Shielded, twisted- pair, PTFE interconnect
cables of minimum length are recommended between the calibrator and
the multimeter. Cable shields should be earth ground referenced. This
configuration is recommended for optimal noises and settling time
performance during calibration.
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