Performance Verification Tests
The performance verification tests are recommended as acceptance tests when you first receive the instrument. The
acceptance test results should be compared against the 90 day test limits. You should use the 24 hour test limits only
for verification within 24 hours after performing the adjustment procedure. After acceptance, you should repeat the
performance verification tests at every calibration interval.
If the instrument fails performance verification, adjustment or repair is required.
Adjustment is recommended at every calibration interval. If adjustment is not made, you must establish a guard band,
using no more than 80% of the specifications, as the verification limits.
Input Connections
Test connections to the instrument are best accomplished using an Agilent Technologies 34172B calibration short for
low–thermal offset measurements and a 34171B DMM connector configured to interface to the calibrator output.
Shielded, twisted–pair, PTFE interconnect cables of minimum length are recommended between the calibrator and the
multimeter to reduce settling and noise errors. HI and HI Sense should be a twisted pair. LO and LO Sense should be a
twisted pair. Cable shields should be earth ground referenced. This configuration is recommended for noise reduction
and settling time performance during calibration.
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:
l Ensure that the calibration ambient temperature (Tcal) is stable and between 18 °C and 28 °C. Ideally the
calibration should be performed at 23 °C ±2 °C.
l Ensure ambient relative humidity is less than 80%.
l Allow a 90 minute warm–up period with a copper short connected.
l 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 care to ensure that the
calibration standards and test procedures 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 2-wire ohms measurements, remove lead resistance by doing a null measurement with the leads shorted or with a
precision 4–terminal low thermal short. For offset calibration a 4–terminal low thermal short is required.
Agilent Truevolt Series DMM Operating and Service Guide 313
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