NI PXIe-4081 Use and care manual

CALIBRATION PROCEDURE
PXIe-4081
PXIe, 7½-Digit, ±1,000 V, Onboard 1.8 MS/s Isolated Digitizer, PXI
Digital Multimeter
This document contains the verification and adjustment procedures for the PXIe-4081. Refer
to ni.com/calibration for more information about calibration solutions.
Contents
Required Software.....................................................................................................................1
Related Documentation.............................................................................................................2
Password................................................................................................................................... 2
Calibration Interval................................................................................................................... 2
Test Equipment..........................................................................................................................2
Calibration Procedures..............................................................................................................3
Initial Setup............................................................................................................................... 3
Test Conditions..........................................................................................................................4
As-Found and As-Left Limits................................................................................................... 4
Verification................................................................................................................................5
Verifying DC Voltage........................................................................................................5
Verifying AC Voltage........................................................................................................7
Verifying 4-Wire Resistance............................................................................................. 9
Verifying 2-Wire Resistance........................................................................................... 11
Verifying DC Current......................................................................................................14
Verifying AC Current......................................................................................................17
Adjustment.............................................................................................................................. 19
Adjusting DC Voltage..................................................................................................... 19
Adjusting Resistance.......................................................................................................20
Adjusting AC Voltages....................................................................................................23
Adjusting Current............................................................................................................25
Completing the Adjustment Procedures......................................................................... 27
Reverification..........................................................................................................................27
Worldwide Support and Services............................................................................................ 28
Required Software
Calibrating the PXIe-4081 requires you to install the following software on the calibration
system:
• NI-DMM version 15.2 or later

You can download all required software from ni.com/downloads.
Related Documentation
For additional information, refer to the following documents as you perform the calibration
procedure:
•NI Digital Multimeters Help
•NI PXIe-4080/4081/4082 Getting Started Guide
•NI PXIe-4081 Specifications
Visit ni.com/manuals for the latest versions of these documents.
Password
The default password for password-protected operations is NI.
Calibration Interval
Recommended calibration interval 2 years
Test Equipment
The following table lists the equipment required for calibrating your device. If you do not have
the recommended instruments, use these specifications to select a substitute calibration
standard.
Equipment Recommended
Models
Where Used Minimum Requirements
Multifunction
calibrator
Fluke 5720A or
Fluke 5730A
Voltage, Current,
Resistance
Maintained at 90 day
specifications
Three sets of low
thermal
electromotive force
(EMF) copper
cables
Fluke 5440 Voltage and
>1 mA Current
(1 set),
Resistance (2
sets), ≤1 mA
Current (3 sets)
Shielded twisted pair copper
cables with copper or gold-
plated copper banana plugs
Banana shorting bar Pomona 5145 DCV, 2-Wire
Resistance
≤ 40 mΩ resistance
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Equipment Recommended
Models
Where Used Minimum Requirements
Double banana plug
with binding posts
Pomona 5405 2-Wire
Resistance
Gold-plated copper
Two insulated low
thermal EMF spade
lugs
Pomona 2305 2-Wire
Resistance
Gold-plated copper
Ammeter Keysight 3458A ≤1 mA DC
Current
• ≤ 40 ppm uncertainty
(100 µA and 1 mA
ranges)
• Optional:
– ≤ 160 ppm
uncertainty (10 µA
range)
– ≤ 300 ppm
uncertainty (1 µA
range)
Calibration Procedures
The calibration process includes the following steps:
•Initial Setup - Set up the test equipment.
•Verification Procedures - Verify the existing operation of the device. This step confirms
whether the device is operating within its specified range prior to calibration.
•Adjustment Procedures - Perform an external adjustment of the device that adjusts the
calibration constants with respect to standards of known values.
•Reverification - Repeat the verification procedure to ensure that the device is operating
within its specifications after adjustment.
Initial Setup
Note Ensure that both the calibrator and the PXIe-4081 are warmed up for at least
60 minutes before you begin this procedure.
To set up the test equipment, complete the following steps:
1. Remove all connections from the four inputs on the PXIe-4081.
2. Verify that the calibrator has been calibrated within the time limits specified in the Test
Equipment section, and that DC zeros calibration has been performed within the last 30
days. Consult the calibrator user documentation for instructions.
PXIe-4081 Calibration Procedure | © National Instruments | 3

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.
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Verification
The performance verification procedures assume that adequate traceable uncertainties are
available for the calibration references.
You can use the verification procedures described in this section for both pre-adjustment and
post-adjustment verification. You can omit sections (for example, the Verifying AC Current
section), however, any function not verified during post-adjustment will no longer be traceable
and should not be used for measurements.
Note Self-calibrate the PXIe-4081 before performing the verification procedures.
Verifying DC Voltage
Complete the following steps to verify DC voltage:
1. Plug in the shorting bar between the HI and LO terminals of the PXIe-4081.
2. Wait two minutes for thermal EMF to stabilize.
3. Reset the PXIe-4081.
4. Initialize the PXIe-4081 for DC voltage with a range of 100 mV and resolution of
7.5 digits.
5. Verify the accuracy for each configuration in the following table:
a) Acquire the measurement at each specified range and input resistance.
b) Compare to the specified limits.
DMM Settings As-Found Limits As-Left Limits
Range Input Resistance Lower Upper Lower Upper
100 mV >10 GΩ / 10 MΩ -2.80 µV 2.80 µV -2.50 µV 2.50 µV
1 V >10 GΩ / 10 MΩ -4.5 µV 4.5 µV -2.8 µV 2.8 µV
10 V >10 GΩ / 10 MΩ -7 µV 7 µV -7 µV 7 µV
100 V 10 MΩ -0.25 mV 0.25 mV -0.20 mV 0.20 mV
1000 V 10 MΩ -0.5 mV 0.5 mV -0.5 mV 0.5 mV
6. Remove the shorting bar from the PXIe-4081.
7. Set the calibrator to Standby.
8. Connect the PXIe-4081 to the calibrator using low thermal EMF cables according the
following figure.
PXIe-4081 Calibration Procedure | © National Instruments | 5