National Instruments NI-9208 Manual

CALIBRATION PROCEDURE
NI 9208
16-channel, ±20 mA, 24-Bit Analog Input Module
This document contains the verification and adjustment procedures for the National
Instruments 9208. For more information on calibration, visit ni.com/calibration.
Contents
Software.................................................................................................................................... 1
Documentation.......................................................................................................................... 2
Test Equipment......................................................................................................................... 3
Test Conditions......................................................................................................................... 3
Initial Setup............................................................................................................................... 3
Verification ............................................................................................................................... 4
Accuracy Verification....................................................................................................... 4
Adjustment................................................................................................................................ 5
Current Accuracy Adjustment .......................................................................................... 5
EEPROM Update ..................................................................................................................... 6
Reverification ........................................................................................................................... 6
Accuracy Under Calibration Conditions .................................................................................. 7
Worldwide Support and Services ............................................................................................. 7
Software
Calibrating the NI 9208 requires the installation of NI-DAQmx 9.1 or later on the calibration
system. You can download NI-DAQmx from ni.com/downloads. NI-DAQmx supports
LabVIEW, LabWindows™/CVI™, C/C++, C#, and Visual Basic .NET. When you install
NI-DAQmx you only need to install support for the application software that you intend to use.
ni.com/manuals
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2|ni.com |NI 9208 Calibration Procedure
Documentation
Consult the following documents for information about the NI 9208, 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 9208 Operating Instructions and Specifications
NI 9208 specific information, specifications, and calibration interval
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

NI 9208 Calibration Procedure |© National Instruments |3
Test Equipment
Table 1 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 in Table 1.
Test Conditions
The following setup and environmental conditions are required to ensure the NI 9208 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 ± 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 NI 9208 measurement
circuitry is at a stable operating temperature.
Initial Setup
Complete the following steps to set up the NI 9208.
1. Install the NI-DAQmx driver software.
2. Make sure the NI cDAQ-9178 power source is not connected.
3. Install the NI 9208 in slot 8 of the NI cDAQ-9178 chassis. Leave slots 1 through 7 of the
NI cDAQ-9178 chassis empty.
4. Connect the NI cDAQ-9178 chassis to your host computer.
5. Connect the power source to the NI cDAQ-9178 chassis.
6. Launch Measurement & Automation Explorer (MAX).
7. Right-click the device name and select Self-Test to ensure that the device is working
properly.
Table 1. Recommended Equipment
Equipment
Recommended
Model Minimum Requirements
Source Fluke 5700A Use a high-precision current source with an
accuracy ≤100 ppm.
cDAQ Chassis NI cDAQ-9178 —
Connection Accessory NI 9923 —

4|ni.com |NI 9208 Calibration Procedure
Verification
The following performance verification procedure describes the sequence of operation and
provides test points required to verify the NI 9208. 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 9208.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9208 to the calibrator as shown in Figure 1.
Figure 1. NI 9208 Pin Assignments
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 current to a Test Point value indicated in Table 4.
4. Set the calibrator to Operate mode (OPR).
5. Acquire and average samples.
a. Create an AI current task on the NI 9208 according to Table 2.
1 Connections when using a calibrator with a guard connection.
2 Connections when using a calibrator with no guard connection.
Table 2. NI 9208 Configuration for Current Accuracy Verification
Input Range
Scaled Units Terminal ConfigurationMin Max
-0.02 0.02 Amps RSE
NI 9208Calibrator
COM
AIx
HI
LO
Guard
NI 9208Calibrator
COM
AIx
HI
LO
12

NI 9208 Calibration Procedure |© National Instruments |5
b. Configure the AI current task timing according to Table 3. Set the ADC timing mode
to high-resolution.
c. Start the task.
d. Average the readings.
e. Clear the task.
6. Compare the average to the limits in Table 4.
7. Set the calibrator to Standby mode (STBY).
8. Repeat steps 5 through 7 with the ADC timing mode on the NI 9208 set to high-speed.
9. Repeat steps 3 through 8 for each test point in Table 4.
10. Disconnect the calibrator from the device.
11. Repeat steps 2 through 10 for each channel on the NI 9208.
Adjustment
The following performance adjustment procedure describes the sequence of operation required
to adjust the NI 9208.
Current Accuracy Adjustment
Complete the following steps to adjust the current accuracy of the NI 9208.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9208 to the calibrator as shown in Figure 1.
3. Adjust the NI 9208 current accuracy.
a. Initialize a calibration session on the NI 9208. The default password is NI.
b. Input the external temperature in degrees Celsius.
Table 3. NI 9208 Current Timing Configuration
ADC Timing Mode Sample Mode Samples to Read
High-Resolution N Samples 5
High-Speed N Samples 75
Table 4. NI 9208 Test Limits for Current Accuracy Verification
Range (A) Test Point 1-Year Limits
Minimum Maximum Location Value (A) Lower Limit (A) Upper Limit (A)
-0.022000 0.022000 Positive FS 0.021000 0.020968 0.021032
-0.022000 0.022000 Mid 0.000000 -0.000004 0.000004
-0.022000 0.022000 Negative FS -0.021000 -0.021032 -0.020968

6|ni.com |NI 9208 Calibration Procedure
c. Call the NI 9208 get C Series adjustment points function to obtain an array of
recommended calibration currents for the NI 9208.
d. Set the calibrator to a reference value determined by the array of recommended
calibration currents.
e. Set the calibrator to Operate mode (OPR).
f. Call and configure the NI 9208 gain instance of the adjustment function according to
Table 5.
g. Set the calibrator to Standby mode (STBY).
h. Repeat steps d through g for each calibration current in the array.
i. Disconnect the calibrator from the NI 9208.
j. Call and configure the NI 9208 offset instance of the adjustment function for the
current channel.
k. Close the calibration session.
4. Repeat steps 1 through 3 for each channel on the NI 9208.
EEPROM Update
When an adjustment procedure is completed, the NI 9208 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 Worldwide
Support and Services for assistance in returning the device to NI.
Table 5. Gain Adjustment Configuration
Physical Channel Reference Value
cDAQMod8/aixThe reference value from the array of adjustment points

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Accuracy Under Calibration Conditions
The following accuracy table is valid for calibration under the following conditions:
• Ambient temperature of 23 ± 5 °C
• NI 9208 installed in slot 8 of an NI cDAQ-9178 chassis
• Slots 1 through 7 of the NI cDAQ-9178 chassis are empty
Note The test limits listed in Table 4 are derived using the values in Table 6.
Note For operational specifications, refer to the most recent NI 9208 Operating
Instructions and Specifications online at ni.com/manuals.
Worldwide Support and Services
The National Instruments 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.
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events.
Table 6. NI 9208 Accuracy Under Calibration Conditions
Percentage of Reading Percentage of Range*
0.132% 0.010%
* Range equals 22 mA.