NI 9945 or NI 9944 with an NI 9237 Connection Guide - KnowledgeBase - Support

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NI 9945 or NI 9944 with an NI 9237 Connection Guide

Primary Software: Utility Software>>Measurement & Automation Explorer
Primary Software Version: 4.0
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: CompactRIO>>Analog Input Modules>>NI 9237, CompactRIO>>Analog Input Modules>>NI 9237

Problem:
How do I connect my strain gauge to a NI 9944 or NI 9945 and NI 9237?

Solution:
In Measurement and Automation Explorer (MAX), there is a connection diagram tab in the task configuration that will dynamically update depending on the configuration. This connection diagram shows how to correctly wire the NI 9944 or NI 9945. Note that CH+ in the diagram is the same as IN+ on the module and in documentation.

To connect a 2 lead strain gauge in this case, connect on lead to pin 0 (EX+), another to pin 1 (CH+ or IN+), and wire pins 1 and 2 together (CH+ or IN+ and QTR).

EX+: Excitation
CH+ or IN+: Channel/Signal input
QTR: Quarter Bridge Completion Terminal

There is a diagram in the NI 9944/9945 Quarter Bridge Completion Accessory User Guide that labels the four pins connections.

To configure the NI 9945 create a global virtual channel within MAX, and set it up to acquire an analog signals » analog input » strain. Select the NI 9237 module and appropriate channel, and name the task. Then configure the task.

Note that if you hold your mouse cursor over the Strain Configuration field, MAX will display the circuit diagram in the bottom right.

In this case, R4 is the strain gauge, and R3 is the resistor to shunt across. All circuitry, with the exception of the strain gauge, is internal.

To access the connection diagram click on the connection diagram tab. Make the connections shown in the diagram.

The final step is to calibrate the strain gauge. Go back to the NI-DAQmx Global Channel tab and select the device tab at the top. Now select strain calibration.

For details about each category and instructions on completing the calibration, click on Help on the bottom.

Note: Configuring the NI 9237 Module in MAX with an NI-DAQmx Global Channel while the 9237 is in a cRIO chassis will not work because the module will not be a DAQmx device. The cRIO chassis will show up under Remote Systems in MAX and will not use the DAQmx functionality.

Related Links:
Product Manuals: NI 9944/9945 Quarter Bridge Completion Accessory User Guide Rev A

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