National Instruments NI 9251 Manual

CALIBRATION PROCEDURE
NI 9251 with mini XLR
2 AI, 3 Vrms, 24 Bit, 102.4 kS/s/ch Simultaneous, AC/DC Coupling
This document contains the verification and adjustment procedures for NI 9251 with
mini XLR. 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 9251 with mini XLR requires the installation of NI-DAQmx 16.1 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 9251 with mini XLR,
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 9251 with mini XLR Getting Started Guide
NI 9251 with mini XLR connection information
NI 9251 with mini XLR Datasheet
NI 9251 with mini XLR 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 5530A
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 1269 —
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Table 1. Recommended Equipment (Continued)
Equipment Recommended Model Requirements
BNC (M) to BNC (M)
Coupler
Pomona Electronics 3533 Characteristic impedance :
50 Ω
BNC F-F-F-T-Connector Pomona Electronics 3284 Characteristic impedance :
50 Ω
mXLR to BNC (M) Cable
(quantity 2)
NI 140150A-XXX
• 0R46 for 0.46 m
• 0R91 for 0.91 m
• 2R4 for 2.4 m —
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.
• Use shielded copper wire for all cable connections to the device. Use twisted-pairs wire
to eliminate noise and thermal offsets.
• 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 9251 with mini XLR.
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.
NI 9251 Calibration Procedure | © National Instruments | 3

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.
Verification
The following performance verification procedure describes the sequence of operation and
provides test points required to verify the NI 9251 with mini XLR. 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 9251 with
mini XLR.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9251 with mini XLR to the calibrator as shown in the following figure.
Figure 1. Analog Input Verification Connections
NI 9251Calibrator
AI0–
AI0+
Chassis GND
HI
LO
AI1+
AI1–
Note The chassis ground lug connection to ground is the
NI 9251 with mini XLR ground connection.
3. Set the calibrator voltage to a Test Point value indicated in the NI 9251 with mini XLR
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 9251 with mini XLR AI Voltage Task Configuration table.
Table 2. NI 9251 with mini XLR AI Voltage Task Configuration
Minimum (V) Maximum (V) Scaled Units Physical Channels Channel Configuration
-4.243 4.243 Volts AI0:1 DC Coupled
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b) Configure the task timing according to the following NI 9251 with mini XLR Timing
Configuration table.
Table 3. NI 9251 with mini XLR Timing Configuration
Sample Mode Samples Per Channel Rate (kS/s)
Finite Samples 10240 102.4
c) Start the task.
d) Read the samples from the NI 9251 with mini XLR.
e) Average the samples for each AI channel.
f) Clear the task.
6. Set the calibrator to Standby mode (STBY).
7. Compare the averaged samples to the limits in the NI 9251 with mini XLR Verification
Test Limits table to verify the input accuracy. If the value is within these limits, the device
passes the test.
8. Repeat steps 3 through 7 for each test point in the NI 9251 with mini XLR Verification
Test Limits table.
9. Disconnect the calibrator from the device.
Table 4. NI 9251 with mini XLR Verification Test Limits
Test Point 2-Year Limits
Location Value (V) Lower Limit (VDC) Upper Limit (VDC)
Minimum -1.9 -1.905161 -1.894839
Mid-scale 0 -0.002885 0.002885
Maximum 1.9 1.894839 1.905161
Note The test limits listed in the NI 9251 with mini XLR Verification Test Limits
table are derived using values from the NI 9251 with mini XLR Accuracy Under
Calibration Conditions table.
Adjustment
The following performance adjustment procedure describes the sequence of operation required
to adjust the NI 9251 with mini XLR.
Accuracy Adjustment
Complete the following procedure to adjust the accuracy performance of the
NI 9251 with mini XLR.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9251 with mini XLR to the calibrator as shown in the Accuracy
Verification section.
NI 9251 Calibration Procedure | © National Instruments | 5

3. Adjust the NI 9251 with mini XLR.
a) Initialize a calibration session on the NI 9251 with mini XLR. The default password
is NI.
b) Input the external temperature in degrees Celsius.
c) Call the NI 9251 with mini XLR get C Series adjustment points function to obtain an
array of recommended calibration voltages for the NI 9251 with mini XLR.
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 9251 with mini XLR adjustment function according to
NI 9251 with mini XLR Adjustment Configuration table.
Table 5. NI 9251 with mini XLR Adjustment Configuration
Physical Channel Reference Value
cDAQ1Mod8/AI0:1 The 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 9251 with mini XLR from the calibrator.
EEPROM Update
When an adjustment procedure is completed, the NI 9251 with mini XLR 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.
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The following accuracy table is valid for calibration under the following conditions:
• Ambient temperature 23 °C ± 5 °C
• NI 9251 with mini XLR installed in slot 8 of an NI cDAQ-9178 chassis
• Slots 1 through 7 of the NI cDAQ-9178 chassis are empty
Table 6. NI 9251 with mini XLR Accuracy under Calibration Conditions
Device Percent of Reading (Gain Error) Percent of Range1
NI 9251 with mini XLR ±0.1198% ±0.0680%
Note For operational specifications, refer to the most recent
NI 9251 with mini XLR 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 NI Factory Installation Services, repairs, extended warranty, and
other services.
Visit ni.com/register to register your NI product. Product registration facilitates technical
support and ensures that you receive important information updates from NI.
A Declaration of Conformity (DoC) is our claim of compliance with the Council of the
European Communities using the manufacturer’s declaration of conformity. This system
affords the user protection for electromagnetic compatibility (EMC) and product safety. You
can obtain the DoC for your product by visiting ni.com/certification. If your product supports
calibration, you can obtain the calibration certificate for your product at ni.com/calibration.
NI corporate headquarters is located at 11500 North Mopac Expressway, Austin, Texas,
78759-3504. NI also has offices located around the world. For telephone support in the United
States, create your service request at ni.com/support or dial 1 866 ASK MYNI (275 6964). For
telephone 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,
support phone numbers, email addresses, and current events.
1Range equals 4.243 V.
NI 9251 Calibration Procedure | © National Instruments | 7

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376360A-01 April 10, 2017