©
National Instruments Corporation
5
NI 4070/4072 Calibration Procedure
Additional Requirements for the NI 4072
The following equipment is required for calibrating the capacitance and
inductance modes of the NI 4072:
•
25
Ω
, 125
Ω
, 5 k
Ω
, and 100 k
Ω
resistors with thermal drift
≤
5 ppm/°C
and tolerance
≤
1%. The distance between the resistor leads and the
NI 4072 terminals should be
≤
1 in.
•
Verification capacitors calibrated to at least four times the accuracy of
the NI 4072, with temperature coefficients
≤
250 ppm/°C. The values
of the verification capacitors should cover the complete capacitance
range. NI suggests using traceable capacitor standards with values
≥
10% of full range for all ranges, except the 300 pF range. For the
300 pF range, a capacitor with values between 90–100% of full scale
should be used. NI suggests using the capacitance standards of the
SCA Series from IET Labs. This calibration procedure assumes the use
of 270 pF, 1 nF, 100 nF, 10
μ
F, and 1000
μ
F standards.
•
If you are using cables to connect the verification capacitors to the
NI 4072 banana plug connectors, NI recommends using Pasternack
PE3005 banana-to-banana coaxial cables with length
≤
4 inches and
total capacitance
≤
40 pF. Before performing the verification
procedure, you should know the total capacitance up to the end of the
banana connectors that plug into the NI 4072.
Test Conditions
Follow these guidelines to optimize the connections and the environment
during calibration:
•
Ensure that the PXI chassis fan speed is set to
HI
(if calibrating the
NI PXI-4070/4072) and that the fan filters are clean.
•
Use PXI filler panels in all vacant slots to allow proper cooling.
•
Plug the PXI chassis or PC and the calibrator into the same power strip
to avoid ground loops.
•
Power on and warm up both the calibrator and the NI 4070/4072 for at
least 60 minutes before beginning this calibration procedure.
•
Maintain an ambient temperature of 23 ±1 °C.
•
Maintain an ambient relative humidity of less than 60%.
•
Allow the calibrator to settle fully before taking any measurements.
Consult the Fluke 5700A/5720A user documentation for instructions.
•
Allow the thermal EMF enough time to stabilize when you change
connections to the calibrator or the NI 4070/4072. The suggested time
periods are stated where necessary throughout this document.
•
Keep a shorting bar connected between the
V GUARD
and
GROUND binding posts of the calibrator at all times.
