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© National Instruments Corporation 37 NI 4070/4072 Calibration Procedure
Verifying Capacitance and Inductance (NI 4072 Only)
This verification procedure only applies to the NI 4072 and requires
additional test equipment, as indicated in the Additional Requirements for
the NI 4072 section.
Note The NI 4072 inductance accuracy is theoretically verified if the capacitance
accuracy meets the specifications. If you have access to precision inductors, you can verify
the inductance measurements by comparing your results with the published accuracy
specifications.
NI suggests using traceable capacitor standards with low thermal drift. You
can use different verification capacitors to verify each capacitance range.
You can verify two ranges with the same verification capacitor as long as
its value is ≥10% of the higher capacitor range. For example, you can use a
1 nF verification capacitor to test both the 10 nF and 1 nF ranges.
After taking each measurement, verify that the measurement falls between
the tolerances listed in Table 22. Tolerances are provided instead of
absolute limits, because you can use capacitance verification values other
than the values suggested, or the calibrated value may differ slightly from
the nominal capacitance (for example, 272.43 pF instead of 270.00 pF).
The tolerances shown in Table 22 correspond to the NI 4072 accuracy
specifications.
The following verification procedure assumes the use of verification
capacitors with the following values: 270 pF, 1 nF, 100 nF, 10 μF, and
1000 μF.
The configuration of the cables and fixtures should be consistent
throughout each measurement. If you are using cables to connect the
verification capacitors to the NI 4072 banana plug connectors, minimize
noise by ensuring that the cables remain fixed and do not move during the
measurement.
Keep direct contact with the verification capacitors to a minimum so that
they are constantly kept at the ambient temperature. After connecting a
capacitor to the NI 4072 terminals, NI recommends waiting 30 seconds for
the capacitor temperature to stabilize.
Note You should know the total capacitance up to the banana connectors that plug into the
NI 4072 before performing the verification procedure.