Test Conditions
The following setup and environmental conditions are required to ensure the PXIe-4081 meets
published specifications:
•
Ensure that the PXI Express chassis fan speed is set to HIGH and that the fan filters are
clean.
•
Use PXI Express filler panels in all vacant slots to allow proper cooling.
•
Plug the PXI Express chassis and the calibrator into the same power strip to avoid ground
loops.
•
Power on and warm up both the calibrator and the PXIe-4081 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 80%.
•
Allow the calibrator to settle fully before taking any measurements. Consult the calibrator
user documentation for instructions.
•
Allow the thermal EMF enough time to stabilize when you change connections to the
calibrator or the PXIe-4081. 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.
•
Clean any oxidation from the banana plugs on the cables before plugging them into the
binding posts of the calibrator or the connectors of the PXIe-4081. Oxidation tarnishes
the copper plugs so that they appear dull rather than shiny and leads to greater thermal
EMF.
•
Prevent the cables from moving or vibrating by taping or strapping them to a
nonvibrating surface. Movement or vibration causes triboelectric effects that can result in
measurement errors.
As-Found and As-Left Limits
The
as-found limits
are the published 2-year specifications for the device. NI uses these limits
to determine whether the device meets the device specifications when it is received for
calibration.
The
as-left limits
are based on the published 24-hour specifications for the device, with
consideration for measurement uncertainty. NI uses these limits to determine whether the
device will meet the device specifications over its calibration interval.
Where a TUR of less than 4:1 was determined, a guardband technique was applied to the test
limits to maintain the same Probability of False Accepts (PFA) as if it was 4:1. The method
selected was the ANSI/NCSL Z540.3 method 6: Guard Bands Based on Test Uncertainty
Ratio.
4
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PXIe-4081 Calibration Procedure
