National Instruments 9252 Manual

CALIBRATION PROCEDURE
NI 9252
8 AI, ±10 V, 24 bit, 50 kS/s/ch Simultaneous
This document contains the verification and adjustment procedures for NI 9252. 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................................................................................................................................3
Accuracy Verification....................................................................................................... 3
Adjustment................................................................................................................................ 5
Accuracy Adjustment........................................................................................................5
EEPROM Update......................................................................................................................6
Reverification............................................................................................................................6
Accuracy under Calibration Conditions....................................................................................6
Revision History....................................................................................................................... 7
Worldwide Support and Services.............................................................................................. 7
Software
Calibrating the NI 9252 requires the installation of NI-DAQmx 19.1 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 9252, 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 9252 Getting Started Guide
NI 9252 connection information
NI 9252 Datasheet
NI 9252 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 Use a high-precision DC voltage source
with a gain uncertainty of <57 ppm and an
offset uncertainty of <0.6 mV.
Chassis NI cDAQ-9178 —
DSUB Connection
Accessory1
NI 9923 —
1For NI 9252 with DSUB variant
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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.
• 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 9252.
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.
Verification
The following performance verification procedure describes the sequence of operation and
provides test points required to verify the NI 9252. 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 9252.
NI 9252 Calibration Procedure | © National Instruments Corporation | 3

1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9252 to the calibrator as shown in the following figure.
Figure 1. Analog Input Verification Connections
NI 9252Calibrator
AIx–
AIx+
COM
HI
LO
Guard
NI 9252Calibrator
AIx–
AIx+
COM
HI
LO
12
1. Connections when using a calibrator with a guard connection.
2. Connections when using a calibrator with no guard connection.
Note If the calibrator outputs are truly floating, connect the negative output to
a quiet earth ground as well as COM to give the entire system a ground
reference.
3. Set the calibrator voltage to a Test Point value indicated in the NI 9252 Verification Test
Limits table.
4. Set the calibrator to Operate mode (OPR).
5. Acquire and average samples.
a) Create and configure an AI voltage channel according to the following NI 9252 AI
Voltage Task table.
Table 2. NI 9252 AI Voltage Task
Physical Channels Range Terminal Configuration
cDAQMod8/AI0:7 ±10.5 V Differential
b) Configure the AI voltage channel timing according to the following NI 9252 Task
Timing table.
Table 3. NI 9252 Task Timing
Samples Per Channel Acquisition Mode Rate (kS/s)
1000 Finite Samples 50
c) Set the filter frequency to 3125 Hz using the Channel Property ( Analog Input »
General Properties »Filter »Frequency ).
d) Start the task.
e) Read the samples from the NI 9252.
f) Average the samples.
g) Clear the task.
6. Compare the averaged samples to the limits in the NI 9252 Verification Test Limits table
to verify the input accuracy. If the values are within these limits, the device passes the
test.
7. Set the calibrator to Standby mode (STBY).
4| ni.com | NI 9252 Calibration Procedure

8. Repeat steps 3 through 7 for each test point in the NI 9252 Verification Test Limits table.
9. Disconnect the calibrator from the device.
Table 4. NI 9252 Verification Test Limits
Test Points 2-Year Limits
Location Value (VDC) Lower Limit (VDC) Upper Limit (VDC)
Min -10.0000 -10.0166 -9.9834
Mid 0.0000 -0.0026 0.0026
Max 10.0000 9.9834 10.0166
Note The test limits listed in the NI 9252 Verification Test Limits table are derived
using values from the NI 9252 Accuracy Under Calibration Conditions table.
Adjustment
The following performance adjustment procedure describes the sequence of operation required
to adjust the NI 9252.
Accuracy Adjustment
Complete the following procedure to adjust the accuracy performance of the NI 9252.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9252 to the calibrator as shown in the Accuracy Verification section.
3. Adjust the NI 9252.
a) Initialize a calibration session on the NI 9252. The default password is NI.
b) Input the external temperature in degrees Celsius.
c) Call the NI 9252 get C Series adjustment points function to obtain an array of
recommended calibration voltages for the NI 9252.
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 9252 adjustment function according to NI 9252
Adjustment Configuration table.
Table 5. NI 9252 Adjustment Configuration
Physical Channel Reference Value
cDAQ1Mod8/AI0:7 The actual value of the voltage output of the calibrator
Note The module acquisition is started each time the adjust function is
called. There is a delay of approximately 550 µs from the acquisition start
until module data becomes available.
NI 9252 Calibration Procedure | © National Instruments Corporation | 5

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.
j) Clear the task.
4. Disconnect the NI 9252 from the calibrator.
EEPROM Update
When an adjustment procedure is completed, the NI 9252 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 9252 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 9252 Accuracy under Calibration Conditions
Device Percent of Reading (Gain Error) Percentage of Range (Offset Error)2
NI 9252 0.14% 0.025%
Note For operational specifications, refer to the most recent NI 9252 Datasheet
online at ni.com/manuals.
2Range equals 10.5 V.
6| ni.com | NI 9252 Calibration Procedure

Revision History
Part Number Edition Date Section Changes
378062B-01 August 2020 Accuracy
Verification
Added callout notes to the analog input
verification connections figure
Updated Channel Property setting
sequence in step 5.c)
Updated the verification test limits table
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.
NI 9252 Calibration Procedure | © National Instruments Corporation | 7

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378062B-01 September 2, 2020