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Using a Quarter-Bridge Configuration with NI 9237 and NI 9949

Updated Aug 19, 2022

Reported In

Hardware

  • NI-9237
  • NI-9949

Issue Details

The manual of NI 9237 states that you can use a Quarter-Bridge configuration with the NI 9237 if you add a resistor externally to create a Half-Bridge. How can this be done using the NI 9949 accessory box?

Solution

The NI 9237 has two internal resistors for Half-Bridge completion. To connect a strain gage (R4) in the Quarter-Bridge configuration, you need an external precision resistor (R3) to complete the bridge circuit. Wire the strain gage and the precision resistor as shown. For shunt calibration, connect wires across the precision resistor as shown.
The list of pin connections between the NI 9949 and the NI 9237 can be found below:
NI 9949NI 9237 Terminals
Pin 1SCShunt Resistor end 1
Pin 2AI+Channel Input +
Pin 3AI-Channel Input -
Pin 4RS+Remote Sense +
Pin 5RS-Remote Sense -
Pin 6EX+Excitation +
Pin 7EX-Excitation -
Pin 8T+TEDS+
Pin 9T-TEDS-
Pin 10SCShunt Resistor end 2

Additional Information

If you have a shielded strain gage then you need to connect the shield wire of your strain gage to the “S” terminal on NI 9949.

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