Electronic Calibration of the 3458A (Product Note 3458A-3) B
Keysight 3458A Calibration Manual 125
One-time adjustments
The following electronic adjustments are only
performed once at the factory or following repair
of the circuitry involved.
1 Determine the actual frequency value of the
crystal used for frequency and period
measurements.
2 Adjust time base interpolator accuracy.
3 Adjust high frequency response of the AC
attenuator and amplifier by transfer of
accuracy at 100 kHz to 2 MHz and 8 MHz.
Traceability
The above methods result in all functions and
ranges being traceable to one or both of the
internal reference standards. These internal
standards are, in turn, traceable to the external
standards. The problem is knowing the
uncertainty to which they are traceable. The
answer lies in knowing the maximum uncertainty
of each transfer measurement made. The
dominant sources of transfer uncertainty are the
linearity errors of the internal circuits and the
noise of each measurement. Each transfer
measurement contributes some error. With
multiple transfers between ranges, the error is
cumulative.
However, the excellent short-term stability of the
internal references and the superior linearity of
the analog-to-digital converter minimizes these
errors. For example, the cumulative transfer error
for the 3458A multimeter is less than 1 part per
million on the lower three DC volt ranges.
All calibration transfer errors and noise errors are
included in the published accuracy specifications
of the 3458A multimeter.
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