National Instruments NI 9231 Manual
CALIBRATION PROCEDURE
NI 9231
8 AI, ±5 V, 24 Bit, 51.2 kS/s/ch Simultaneous, AC/DC Coupling, IEPE
AC Coupling
This document contains the verification and adjustment procedures for NI 9231. For more
information about calibration solutions, visit ni.com/calibration.
Contents
Software.................................................................................................................................... 1
Documentation.......................................................................................................................... 1
Test Equipment..........................................................................................................................2
Test Conditions..........................................................................................................................3
Initial Setup............................................................................................................................... 3
Verification................................................................................................................................4
Accuracy Verification....................................................................................................... 4
Adjustment................................................................................................................................ 5
Accuracy Adjustment........................................................................................................5
EEPROM Update......................................................................................................................6
Reverification............................................................................................................................6
Accuracy under Calibration Conditions....................................................................................6
Worldwide Support and Services.............................................................................................. 7
Software
Calibrating the NI 9231 requires the installation of NI-DAQmx 18.1 or later on the calibration
system.
You can download NI-DAQmx from ni.com/downloads. NI-DAQmx supports LabVIEW,
LabWindows™/CVI™, ANSI C, and .NET. When you install NI-DAQmx, you only need to
install support for the application software that you intend to use.
Documentation
Consult the following documents for information about the NI 9231, NI-DAQmx, and your
application software. All documents are available on ni.com and help files install with the
software.
NI cDAQ-9174/9178 USB Chassis Quick Start
NI-DAQmx installation and hardware setup
NI 9231 Getting Started Guide
NI 9231 connection information
NI 9231 Datasheet
NI 9231 circuitry and specifications
NI-DAQmx Readme
Operating system and application software support in NI-DAQmx
LabVIEW Help
LabVIEW programming concepts and reference information about NI-DAQmx VIs
and functions
NI-DAQmx C Reference Help
Reference information for NI-DAQmx C functions and NI-DAQmx C properties
NI-DAQmx .NET Help Support for Visual Studio
Reference information for NI-DAQmx .NET methods and NI-DAQmx .NET
properties, key concepts, and a C enum to .NET enum mapping table
Test Equipment
The following table lists the equipment recommended for the performance verification and
adjustment procedures. If the recommended equipment is not available, select a substitute
using the requirements listed.
Table 1. Recommended Equipment
Equipment Recommended Model Requirements
Calibrator Fluke 5502A, Fluke 5522A,
Fluke 5730A
Use a high-precision voltage
source with gain error of
<100 ppm and offset error
<0.1 mV.
BNC (F) to Banana
Adapter Pomona Electronics 1270 —
2| ni.com | NI 9231 Calibration Procedure
Table 1. Recommended Equipment (Continued)
Equipment Recommended Model Requirements
10-32 (M) to BNC (F)
Coupler 769416-01 Characteristic impedance:
50 Ω
Chassis NI cDAQ-9178 —
Test Conditions
The following setup and environmental conditions are required to ensure the device meets
published specifications.
• Keep connections to the device as short as possible. Long cables and wires act as
antennas, picking up extra noise that can affect measurements.
• Verify that all connections to the device are secure.
• Maintain an ambient temperature of 23 °C ± 5 °C. The device temperature will be greater
than the ambient temperature.
• Keep relative humidity below 80%.
• Allow a warm-up time of at least 10 minutes to ensure that the device measurement
circuitry is at a stable operating temperature.
Initial Setup
Complete the following steps to set up the NI 9231.
1. Install NI-DAQmx.
2. Make sure that the NI cDAQ-9178 power source is not connected to the chassis.
3. Connect the NI cDAQ-9178 chassis to the system safety ground.
a) Attach a ring lug to a 14 AWG (1.6 mm) wire.
b) Connect the ring lug to the ground terminal on the side of the NI cDAQ-9178 using
the ground screw.
c) Attach the other end of the wire to the system safety ground.
4. Install the module in slot 8 of the NI cDAQ-9178 chassis. Leave slots 1 through 7 of the
NI cDAQ-9178 chassis empty.
5. Connect the NI cDAQ-9178 chassis to your host computer.
6. Connect the power source to the NI cDAQ-9178 chassis.
7. Launch Measurement & Automation Explorer (MAX).
8. Right-click the device name and select Self-Test to ensure that the module is working
properly.
NI 9231 Calibration Procedure | © National Instruments | 3
Verification
The following performance verification procedure describes the sequence of operation and
provides test points required to verify the NI 9231. The verification procedure assumes that
adequate traceable uncertainties are available for the calibration references.
Accuracy Verification
Complete the following procedure to determine the As-Found status of the NI 9231.
1. Set the calibrator to Standby mode (STBY).
2. Connect channel 0 of the NI 9231 to the calibrator as shown in the following figure.
Figure 1. Analog Input Verification Connections
NI 9231
+
–
HI
LO
Calibrator
AIx
Note The chassis ground lug connection to ground is the NI 9231 ground
connection.
3. Set the calibrator voltage to a Test Point value indicated in the NI 9231 Verification Test
Limits table.
4. Set the calibrator to Operate mode (OPR).
5. Acquire and average samples for each channel.
a) Create and configure an AI voltage task according to the following NI 9231 AI
Voltage Task Configuration table.
Table 2. NI 9231 AI Voltage Task Configuration
Minimum (V) Maximum (V) Scaled Units Physical Channels Channel Configuration
-5 5 Volts AIxDC Coupled
b) Configure the task timing according to the following NI 9231 Timing Configuration
table.
Table 3. NI 9231 Timing Configuration
Sample Mode Samples Per Channel Rate (kS/s)
Finite Samples 5120 51.2
c) Start the task.
d) Read the samples from the NI 9231.
e) Average the samples for each AI channel.
f) Clear the task.
4| ni.com | NI 9231 Calibration Procedure
6. Compare the averaged samples to the limits in the NI 9231 Verification Test Limits table
to verify the input accuracy. If the value is within these limits, the device passes the test.
7. Repeat steps 3 through 7 for each test point in the NI 9231 Verification Test Limits table.
8. Set the calibrator to Standby mode (STBY).
9. Repeat steps 1 through 8 for each channel on the NI 9231.
Table 4. NI 9231 Verification Test Limits
Test Point 2-Year Limits
Location Value (V) Lower Limit (VDC) Upper Limit (VDC)
Minimum -4.9 -4.907121 -4.892879
Mid-scale 0 -0.001565 0.001565
Maximum 4.9 4.892879 4.907121
Note The test limits listed in the NI 9231 Verification Test Limits table are derived
using values from the NI 9231 Accuracy Under Calibration Conditions table.
Adjustment
The following performance adjustment procedure describes the sequence of operation required
to adjust the NI 9231.
Accuracy Adjustment
Complete the following procedure to adjust the accuracy performance of the NI 9231.
1. Set the calibrator to Standby mode (STBY).
2. Connect channel 0 of the NI 9231 to the calibrator as shown in the Accuracy Verification
section.
3. Adjust the NI 9231.
a) Initialize a calibration session on the NI 9231. The default password is NI.
b) Input the external temperature in degrees Celsius.
c) Call the NI 9231 get C Series adjustment points function to obtain an array of
recommended calibration voltages for the NI 9231.
d) Set the calibrator to a reference value determined by the array of recommended
calibration voltages.
e) Set the calibrator to Operate mode (OPR).
f) Call and configure the NI 9231 adjustment function according to NI 9231
Adjustment Configuration table.
NI 9231 Calibration Procedure | © National Instruments | 5
Table 5. NI 9231 Adjustment Configuration
Physical Channel Reference Value
cDAQ1Mod8/AIxThe actual value of the voltage output of the calibrator
g) Set the calibrator to Standby mode (STBY).
h) Repeat steps d through g for each point in the array.
i) Close the calibration session.
4. Disconnect the NI 9231 from the calibrator.
5. Repeat steps 1 through 4 for each channel on the NI 9231.
EEPROM Update
When an adjustment procedure is completed, the NI 9231 internal calibration memory
(EEPROM) is immediately updated.
If you do not want to perform an adjustment, you can update the calibration date and onboard
calibration temperature without making any adjustments by initializing an external calibration,
setting the C Series calibration temperature, and closing the external calibration.
Reverification
Repeat the Verification section to determine the As-Left status of the device.
Note If any test fails Reverification after performing an adjustment, verify that you
have met the Test Conditions before returning your device to NI. Refer to the
Worldwide Support and Services section for assistance in returning the device to NI.
Accuracy under Calibration Conditions
The values in the following table are based on calibrated scaling coefficients, which are stored
in the onboard EEPROM.
The following accuracy table is valid for calibration under the following conditions:
• Ambient temperature 23 °C ± 5 °C
• NI 9231 installed in slot 8 of an NI cDAQ-9178 chassis
• Slots 1 through 7 of the NI cDAQ-9178 chassis are empty
6| ni.com | NI 9231 Calibration Procedure
Table 6. NI 9231 Accuracy under Calibration Conditions
Device Percent of Reading (Gain Error) Percentage of Range (Offset Error)1
NI 9231 ±0.1134% ±0.0313%
Note For operational specifications, refer to the most recent NI 9231 Datasheet
online at ni.com/manuals.
Worldwide Support and Services
The NI website is your complete resource for technical support. At ni.com/support, you have
access to everything from troubleshooting and application development self-help resources to
email and phone assistance from NI Application Engineers.
Visit ni.com/services for information about the services NI offers.
Visit ni.com/register to register your NI product. Product registration facilitates technical
support and ensures that you receive important information updates from NI.
NI corporate headquarters is located at 11500 North Mopac Expressway, Austin, Texas,
78759-3504. NI also has offices located around the world. For support in the United States,
create your service request at ni.com/support or dial 1 866 ASK MYNI (275 6964). For
support outside the United States, visit the Worldwide Offices section of ni.com/niglobal to
access the branch office websites, which provide up-to-date contact information.
1Range equals 5 V.
NI 9231 Calibration Procedure | © National Instruments | 7
Information is subject to change without notice. Refer to the NI Trademarks and Logo Guidelines at ni.com/trademarks for
information on NI trademarks. Other product and company names mentioned herein are trademarks or trade names of their
respective companies. For patents covering NI products/technology, refer to the appropriate location: Help»Patents in your
software, the patents.txt file on your media, or the National Instruments Patent Notice at ni.com/patents. You can find
information about end-user license agreements (EULAs) and third-party legal notices in the readme file for your NI product. Refer
to the Export Compliance Information at ni.com/legal/export-compliance for the NI global trade compliance policy and how
to obtain relevant HTS codes, ECCNs, and other import/export data. NI MAKES NO EXPRESS OR IMPLIED WARRANTIES AS
TO THE ACCURACY OF THE INFORMATION CONTAINED HEREIN AND SHALL NOT BE LIABLE FOR ANY ERRORS. U.S.
Government Customers: The data contained in this manual was developed at private expense and is subject to the applicable
limited rights and restricted data rights as set forth in FAR 52.227-14, DFAR 252.227-7014, and DFAR 252.227-7015.
© 2018 National Instruments. All rights reserved.
378044A-01 June 20, 2018
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