National Instruments RM-26999 Manual

December 2020
RM-26999
Calibration Procedure

RM-26999 Calibration Procedure
© National Instruments Corporation 1
This document contains the verification and adjustment procedures for the
RM-26999. Use the procedures in this document to automate calibration or to
conduct manual calibration. Review and become familiar with the entire procedure
before beginning the calibration process.
Contents
Terms and Definitions ......................................................................................................2
Calibration Overview........................................................................................................2
Calibration Condition Guidelines...............................................................................3
Calibration Resources ......................................................................................................4
Required Software.......................................................................................................4
Recommended Documentation.................................................................................5
Test Equipment ...........................................................................................................5
Initial Equipment Setup ...................................................................................................7
Warm Up the DUT .............................................................................................................8
Perform Verification .........................................................................................................8
DC Gain Verification.....................................................................................................8
AC Gain Verification...................................................................................................12
Perform Adjustment.......................................................................................................17
Initial Test Connection..............................................................................................17
Adjustment Procedure..............................................................................................19
Perform Reverification ...................................................................................................22
Revision History..............................................................................................................22
NI Services.......................................................................................................................23

RM-26999 Calibration Procedure
2ni.com/calibration
Terms and Definitions
DUT DUT is an acronym for Device Under Test, and refers to the NI product being
calibrated. For this procedure, DUT refers to the RM-26999.
As-Found Limits These limits are derived from the published specifications for the DUT. NI
uses these limits to determine if the DUT is performing within the
recommended calibration interval specifications at the time of calibration
and before any adjustment is performed.
As-Left Limits These limits are derived from the published specifications for the DUT minus
guardband to ensure a high probability that the DUT will meet its
specifications over the next recommended calibration interval.
Functional Test Functional Tests determine whether the DUT is operating correctly.
Functional tests are not directly related to performance specifications.
Verification Verification evaluates the measured calibration results against the defined
As-Found Limits. The result of the evaluation is expressed as a Pass/Fail
condition in the calibration certificate using an established evaluation
formula.
Adjustment Adjustment performs a set of operations on the DUT to optimize the
measurement performance and conform it to the assigned calibrated values.
Reverification Reverification evaluates the measured calibration results against the As-Left
limits after adjustment. The As-Left limits may be tighter than the As-Found
limits.
Recommended
Calibration
Interval
This interval indicates the recommended period between each round of
verification and adjustment of the DUT. There is a high probability that,
within this interval, the DUT will remain within the published warranted
performance specifications. Some measurement DUTs have warranted
specifications for different calibration intervals, for example: 24 hours, 90
days, 1 year, and 2 years. In this case, the specification depends on the
calibration cycle chosen by the user.
Calibration Overview
Recommended Calibration Interval
1 year

RM-26999 Calibration Procedure
© National Instruments Corporation 3
Password
NI
Note
This is the default password for all password-protected operations. This
password is site-specific.
Task Estimated Test Time Operator Connections Test Points
Setup 5 minutes 8 connections —
Warm Up 30 minutes — —
Verify, Adjust, and Reverify 35 minutes 28 connections 88 points
Verify only 15 minutes 8 connections 41 points
Adjust only 5 minutes 12 connections 6 points
Note
Estimated test times assume the user is conducting a manual calibration.
For most procedures, automating the calibration significantly reduces test
times.
Environmental Conditions for Calibration
Ambient temperature 23 °C ± 5 °C
Relative humidity 20% to 80%
Calibration Condition Guidelines
Keep cabling as short as possible. Long cables act as antennas, picking up extra
noise that can affect measurements.
Ensure that all connections to the DUT are secure.
Allow adequate warm up time for all components of the calibration system.

RM-26999 Calibration Procedure
4ni.com/calibration
Make all connections as shown in diagrams.
Use shielded copper wire for all cable connections to the DUT.
Use twisted-pair wires to eliminate noise and thermal offsets.
Ensure that the PXI/PXI Express chassis fan speed is set to HIGH, that the fan
filters are clean, and that the empty slots contain filler panels. For more
information, refer to the Maintain Forced-Air Cooling Note to Users document
available at ni.com/manuals.
If a DUT fails reverification after adjustment, ensure that the Test Conditions
have been met before returning the DUT to NI.
Allow the calibrator and DMM to settle fully before taking any measurements. NI
recommends a settling time of 10 seconds. Consult the calibrator and DMM user
documentation for more information.
Allow 2 minutes for the thermal EMF to stabilize after changing connections to
the calibrator, DMM, or DUT.
Calibration Resources
Required Software
Note
Ensure that the most recent version of the required driver software is
installed before conducting the calibration.
Install the following software on the calibration system:
LabVIEW 2017 SPI Base/Full/Pro or later
NI-DAQmx 17.0 or later
RM-26999 API from the VI Package Manager

RM-26999 Calibration Procedure
© National Instruments Corporation 5
Recommended Documentation
Go to ni.com/manuals to locate the following documentation for more information
when performing this calibration:
RM-26999 Specifications
RM-26999 Getting Started Guide
RM-26999 User Manual
Test Equipment
This section details the equipment NI recommends for each test performed as part
of this calibration procedure.
NI Calibration Executive Users
Refer to the Calibration Executive Help to find an updated list of test
equipment for this calibration procedure.
Standard Recommended Model Where Used Functional Requirement(s)
Calibrator Fluke 5730A
Verifications:
DC Gain
AC Gain
DC Range: ±1000 V
DC Accuracy: ±20 µV/V
AC Range: ±1000 V
AC Accuracy:
< 100 kHz: ±0.3%
< 1 MHz: ±1.5%
Calibrator Amp Fluke 5725A
Verifications:
AC Gain
AC Range: ±1000 V
AC Accuracy:
< 100 kHz: ±0.3%
< 1 MHz: ±1.5%

RM-26999 Calibration Procedure
6ni.com/calibration
DMM Keysight 3458A
Verifications:
DC Gain
AC Gain
DC Range: ±10 V
DC Accuracy: ±20 µV/V
AC Range: ±10 V
AC Accuracy: <1 MHz: ±0.02%
Low Thermal EMF
Cable with
Banana Plugs
Fluke 5730A-7002
Verifications:
DC Gain
AC Gain
—
BNC (f) to Banana
Plug Adaptor Pomona Model 1269
Verifications:
DC Gain
AC Gain
—
Power Supply NI PS-16
Verifications:
DC Gain
AC Gain
24 V DC, 5 A
BNC (f) to BNC (f)
cable
Verifications:
DC Gain
AC Gain
—
Calibrator Amp
Cable Fluke 842901
Verifications:
AC Gain No substitution.
SMIO (DAQ)
Module
PXIe-6356, PXIe-6358,
PXIe-6366, PXIe-6368,
PXIe-6376, or PXIe-6378
Verifications:
DC Gain
AC Gain
—
DAQ Device Cable NI SH68F-68F-EPM — —

RM-26999 Calibration Procedure
© National Instruments Corporation 7
Initial Equipment Setup
1. Verify that the calibrator has been calibrated within 1 year and that DC Zero
Calibration has been performed within the last 30 days.
Note
Consult the calibrator user documentation for calibration instructions.
2. Verify that the DMM has been calibrated within 1 year. Verify that ACAL (self-
calibration) has been performed within the last 24 hours or when the
temperature drifts more than ±1 °C from last ACAL temperature. The DMM
must also be within ±5 °C from TCAL. TCAL is the temperature at which an
external calibration was performed on the DMM.
Note
Conducting ACAL on the DMM provides additional c
orrection for errors that
result from measurement, such as temperature drift. Refer to the DMM
user
documentation for more information on conducting ACAL. Account for
additional uncertainty if ACAL is not performed correctly or if TCAL
is outside
the bounds of
±
5
°
C.
3. Verify that the calibrator and DMM have warmed up for at least 1 hour before
making any measurements for this procedure.
4. Allow the calibrator and DMM to settle before taking any measurements.
Note
NI recommends a settling time of 10 seconds. Refer to the calibrator and
DMM documentation for more information about manufacturer-
recommended settling times.
5. Clean any oxidation from the banana connectors on the cables before
connecting them to the calibrator, DMM or DUT.
Note
Oxidation tarnishes the copper plugs so that they appear dull rather than
shiny and increases thermal EMF.

RM-26999 Calibration Procedure
8ni.com/calibration
Warm Up the DUT
Warm up time is not required for the DUT prior to taking measurements. All test
equipment used in this procedure require a warm up time of at least 1 hour.
Perform Verification
DC Gain Verification
Test Limits
Table 1: DC Gain Verification Test Limits
High Voltage
Input Value
Low Voltage
Input Value
Calibrator
Range DMM Range
As-Found Test Limit As-Left Test Limit
Lower
Limit
Upper
Limit
Lower
Limit
Upper
Limit
1000 V 5 V 1100 V 10 V - 502 mV + 502 mV - 251 mV + 251 mV
750 V 3.75 V 1100 V 10 V - 377 mV + 377 mV - 189 mV + 189 mV
500 V 2.5 V 1100 V 10 V - 252 mV + 252 mV - 126 mV + 126 mV
200 V 1 V 220 V 1 V - 102 mV + 102 mV - 51 mV + 51 mV
100 V 500 mV 220 V 1 V - 52 mV + 52 mV - 26 mV + 26 mV
10 V 50 mV 11 V 0.1 V - 7 mV + 7 mV - 3 mV + 3 mV
0 V 5 mV 11 V 0.1 V - 2 mV + 2 mV - 1 mV + 1 mV
-10 V 50 mV 11 V 0.1 V - 7 mV + 7 mV - 3 mV + 3 mV
-100 V 500 mV 220 V 1 V - 52 mV + 52 mV - 26 mV + 26 mV
-200 V 1 V 220 V 1 V - 102 mV + 102 mV - 51 mV + 51 mV
-500 V 2.5 V 1100 V 10 V - 252 mV + 252 mV - 126 mV + 126 mV
-750 V 3.75 V 1100 V 10 V - 377 mV + 377 mV - 189 mV + 189 mV
-1000 V 5 V 1100 V 10 V - 502 mV + 502 mV - 251 mV + 251 mV

RM-26999 Calibration Procedure
© National Instruments Corporation 9
Initial Test Connection
Caution: Possibility of Electric Shock
Power off all high-voltage signals before making any connections.
Figure 1: DC Gain Connection
1.
Calibrator
7.
BNC
-2090A
2.
Low
thermal EMF cable with banana plugs
8.
PXIe
-6356
3.
RM
-26999
9.
SH68F
-68F-EPM cable
4.
Power supply
10.
BNC cable
5.
Twisted, shielded power cable
11.
BNC to
banana plug adaptor
6.
SH68F
-68F-EPM cable
12.
DMM

RM-26999 Calibration Procedure
10 ni.com/calibration
Verification Procedure
1. Connect all test equipment except the calibrator, as shown in Figure 1.
Repeat 4 times, once for each channel.
2. Ensure the DUT is identified by the DAQ device.
a. Refer to the RM-26999 Device Enumeration.vi in the
NI Examples Finder.
3. Ensure that the calibrator output is powered off
Caution: Possibility of Electric Shock
Power off all high-voltage signals and set the calibrator to standby before
making any connections.
4. Connect the calibrator output to the appropriate channel on the DUT. Wait
2 minutes for thermal EMF to stabilize.
Repeat 13 times, once for each set of voltage input values.
5. Configure the DMM to measure the appropriate low voltage input value, as
shown in Table 1.
a. Set the DMM range.
b. Implement PRESET before taking the measurement.
c. Set NPLC to 100.
d. Perform ACAL, if ACAL has not been performed within the last
24 hours or if the temperature has drifted more than ±1 °C from last
ACAL temperature.
e. Enable MATH NULL.
6. Configure the calibrator to the appropriate high voltage input value, as
shown in Table 1.
7. Enable the calibrator to source the high voltage input value.

RM-26999 Calibration Procedure
© National Instruments Corporation 11
8. Allow the DMM and calibrator to settle before taking a measurement. NI
recommends a settling time of 10 seconds.
Note
A settling time of 10 seconds accommodates any changes to range,
polarity, and thermal EMF effects that increase the base settling time.
9. Take the measurement with the DMM.
10. Scale the DMM measurement with the coefficients stored on the DUT
EEPROM.
a. RM-26999 Initialize Voltage Channel.vi
b. RM-26999.lib\_getChannelsFromTask.vi
c. RM-26999.lib\_filterPhysicalChannels.vi
d. RM-26999.lib\_retrieveVoltageScaling.vi
e. RM-26999 Close.vi
Note
To find the RM-26999 VIs, navigate to vi.lib»NI»RM-26999»rm-26999.llb
in
the LabVIEW folder.
11. Compare the scaled measurement with the test limits defined in Table 1.
DUT Measurement = DMM Measurement × DUT Gain + DUT Offset
12. Power off the calibrator output.

RM-26999 Calibration Procedure
12 ni.com/calibration
AC Gain Verification
Test Limits
Table 2: AC Gain Verification Test Limits
Frequency
High
Voltage
Input Value
Low Voltage
Input Value
Calibrator
Range
DMM
Range
As-Found Test Limit As-Left Test Limit
Lower Limit Upper Limit Lower Limit Upper Limit
500 Hz
1000 VRMS 5 VRMS 1100 V 10 V -1.0 VRMS +1.0 VRMS -500 mVRMS +500 mVRMS
500 VRMS 2.5 VRMS 1100 V 10 V -513 mVRMS +513 mVRMS -260 mVRMS +260 mVRMS
50 VRMS 0.25 VRMS 22 V 1 V -63 mVRMS +63 mVRMS -30 mVRMS +30 mVRMS
5 VRMS 0.025 VRMS 22 V 0.1 V -18 mVRMS +18 mVRMS -9 mVRMS +9 mVRMS
1 kHz
1000 VRMS 5 VRMS 1100 V 10 V -2.0 VRMS +2.0 VRMS -1.0 VRMS +1.0 VRMS
500 VRMS 2.5 VRMS 1100 V 10 V -1.0 VRMS +1.0 VRMS -500 mVRMS +500 mVRMS
50 VRMS 0.25 VRMS 22 V 1 V -113 mVRMS +113 mVRMS -55 mVRMS +55 mVRMS
5 VRMS 0.025 VRMS 22 V 0.1 V - 80.5 mVRMS +80.5 mVRMS -40 mVRMS +40 mVRMS
5 kHz
1000 VRMS 5 VRMS 1100 V 10 V -9.0 VRMS +9.0 VRMS -4.5 VRMS +4.5 VRMS
500 VRMS 2.5 VRMS 1100 V 10 V -4.5 VRMS +4.5 VRMS -2.1 VRMS +2.1 VRMS
50 VRMS 0.25 VRMS 22 V 1 V -463 mVRMS +463 mVRMS -230 mVRMS +230 mVRMS
5 VRMS 0.025 VRMSRMS 22 V 0.1 V - 80.5mVRMS +80.5 mVRMS -40 mVRMS +40 mVRMS
10 kHz
1000 VRMS 5 VRMS 1100 V 10 V -11.5 VRMS +11.5 VRMS -5.5 VRMS +5.5 VRMS
500 VRMS 2.5 VRMS 1100 V 10 V -5.8 VRMS +5.8 VRMS -2.6 VRMS +2.6 VRMS
50 VRMS 0.25 VRMS 22 V 1 V -588 mVRMS +588 mVRMS -290 mVRMS +290 mVRMS
5 VRMS 0.025 VRMS 22 V 0.1 V - 80.5mVRMS +80.5 mVRMS -40 mVRMS +40 mVRMS
15 kHz
1000 VRMS 5 VRMS 1100 V 10 V -13.5 VRMS +13.5 VRMS -6.5 VRMS +6.5 VRMS
500 VRMS 2.5 VRMS 1100 V 10 V -6.8 VRMS +6.8 VRMS -3.4 VRMS +3.4 VRMS
50 VRMS 0.25 VRMS 22 V 1 V -688 mVRMS +688 mVRMS -340 mVRMS +340 mVRMS
5 VRMS 0.025 VRMS 22 V 0.1 V - 80.5mVRMS +80.5 mVRMS -40 mVRMS +40 mVRMS

RM-26999 Calibration Procedure
© National Instruments Corporation 13
100 kHz
750 VRMS 3.75 VRMS 750 V 10 V -10.1 VRMS +10.1 VRMS -5.0 VRMS +5.0 VRMS
500 VRMS 2.5 VRMS 750 V 10 V -6.8 VRMS +6.8 VRMS -3.4 VRMS +3.4 VRMS
50 VRMS 0.25 VRMS 22 V 1 V -688 mVRMS +688 mVRMS -340 mVRMS +340 mVRMS
5 VRMS 0.025 VRMS 22 V 0.1 V - 80.5mVRMS +80.5 mVRMS -40 mVRMS +40 mVRMS
1 MHz
220 VRMS 1.1 VRMS 220 V 1 V -30.8 VRMS +30.8 VRMS -15.4 VRMS +15.4 VRMS
100 VRMS 0.5 VRMS 220 V 1 V -14.0 VRMS +14.0 VRMS -7.0 VRMS +7.0 VRMS
20 VRMS 0.1 VRMS 22 V 0.1 V -2.8 VRMS +2.8 VRMS -2.4 VRMS +2.4 VRMS
5 VRMS 0.025 VRMS 22 V 0.1 V -713 mVRMS +713 mVRMS -350 mVRMS +350 mVRMS

RM-26999 Calibration Procedure
14 ni.com/calibration
Initial Test Connection
Caution: Possibility of Electric Shock
Power off all high-voltage signals before making any connections.
Figure 2: AC Gain Connection
1
.
Calibrator
7.
NI BNC
-2090A
2
.
Calibrator amp cable
8.
BNC cable
3
.
Calibrator amp
9.
BNC to banana plug adaptor
4
.
Low
thermal EMF cable with banana plugs
10.
DMM
5
.
NI
RM-26999
11.
Power supply
6
.
NI SH68F
-68F-EPM cable

RM-26999 Calibration Procedure
© National Instruments Corporation 15
Verification Procedure
1. Connect all test equipment except the calibrator, as shown in Figure 2.
Repeat 4 times, once for each channel.
2. Ensure that the calibrator output is powered off.
Caution: Possibility of Electric Shock
Power off all high-voltage signals and set the calibrator to standby before
making any connections.
3. Connect the calibrator to the appropriate channel on the DUT. Wait
2 minutes for thermal EMF to stabilize.
Repeat 7 times, once for each frequency setting.
4. Set the calibrator and the DMM to the appropriate frequency defined in
Table 2.
Repeat 4 times, once for each set of voltage input values.
5. Configure the DMM to measure the appropriate low voltage input value,
as defined in Table 2.
a. Implement PRESET before taking the measurement.
b. Set the ACV function to Synchronously sub-sampled computed
true rms technique.
c. NI recommends enabling LFILTER for frequencies below 50 kHz.
d. Perform ACAL, if ACAL has not been performed within the last
24 hours or if the temperature has drifted more than ±1 °C from
last ACAL temperature.
6. Configure the calibrator to the appropriate high voltage input value, as
defined in Table 2.
7. Enable the calibrator to source the high voltage input value.

RM-26999 Calibration Procedure
16 ni.com/calibration
8. Allow the DMM and calibrator to settle before taking a measurement. NI
recommends a settling time of 10 seconds.
Note
A settling time of 10 seconds accommodates any changes to range,
polarity, and thermal EMF effects that increase the base settling time.
9. Take the measurement with the DMM.
10. Scale the DMM measurement with the coefficients stored on the DUT
EEPROM.
a. RM-26999 Initialize Voltage Channel.vi
b. RM-26999.lib\_getChannelsFromTask.vi
c. RM-26999.lib\_filterPhysicalChannels.vi
d. RM-26999.lib\_retrieveVoltageScaling.vi
e. RM-26999 Close.vi
Note
To find the RM-26999 VIs, navigate to vi.lib»NI»RM-26999»rm-26999.llb
the LabVIEW folder.
11. Compare the scaled measurement with the test limits defined in
Table 2.
DUT Measurement = DMM Measurement × DUT Gain + DUT Offset
12. Power off the calibrator output.

RM-26999 Calibration Procedure
© National Instruments Corporation 17
Perform Adjustment
Perform an adjustment at least once within the calibration interval. Adjustment
automatically updates the calibration constants, the date, and the temperature in
the DUT EEPROM. If the DUT passes the verification procedures within the As-Left
test limits, an adjustment is not required.
Note
NI recommends an adjustment to optimize the measurement performance
of the DUT even if it passes verification within the As-Left limits.
Initial Test Connection
Caution: Possibility of Electric Shock
Power off all high-voltage signals before making any connections.

RM-26999 Calibration Procedure
18 ni.com/calibration
Figure 3: DC Gain Connection
1.
Calibrator
6.
BNC cable
2.
Low
thermal EMF cable with banana plugs
7.
BNC to banana plug adaptor
3.
NI RM
-26999
8.
DMM
4.
NI SH68F
-68F-EPM cable
9.
Power supply
5.
NI
BNC-2090A

RM-26999 Calibration Procedure
© National Instruments Corporation 19
Adjustment Procedure
1. Connect all test equipment except the calibrator, as shown in Figure 3.
2. Call RM-26999 Open External Calibration.vi.
Note
Do not call RM-26999 Close External Calibration.vi before
completing all adjustment steps. Closing the session early will invalidate
all adjustments and measurements.
3. Call RM-26999 Configure DC Calibration Stimulus.vi.
a. Use the high voltage values from Table 3 as input for the VI.
Repeat 2 times, once for each polarity.
Repeat 4 times, once for each channel.
4. Power off the calibrator output.
Caution: Possibility of Electric Shock
Power off all high-voltage signals before making any connections.
5. Connect the calibrator output to channel 1 on the DUT.
Repeat 4 times, once for each set of voltage values.
Table 3: DC Adjustment Test Points
High Voltage Value Calibrator Range Low Voltage Value DMM Range
995 V
1100 V
4.975 V
10 V
500 V 2.5 V
200 V
220 V
1 V
1 V
-200 V -1 V
-500 V
1100 V
-2.5 V
10 V
-995 V -4.975 V