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When Should I Provide an External Voltage to NI 9237 Module?

Updated Nov 23, 2021

Reported In

Hardware

  • NI-9237

Issue Details

I am using the NI-9237 to measure some bridge-based sensors and I am not sure if I have to use external or internal excitation. When do I have to connect an external excitation supply?

Solution

When you use internal excitation, the total power consumed by the sensors has to be below 150 mW. The NI 9237 automatically reduces internal excitation voltages as needed to stay below 150 mW.
  • Although the sensor industry does not recognize a single standard excitation voltage level, excitation voltage levels of between 2.5 V and 10 V are common. You can program the NI 9237 to supply 2.5 V, 3.3 V, 5 V, or 10 V of excitation voltage, and the module can provide up to 150 mW of excitation power.
If your sensors consume more than150 mW, you have to use external excitation to provide more power. 
  • Refer to page 6 of the NI 9237 Datasheet to learn more about how to calculate the power required by your sensor. 

Additional Information

Refer to Use of External Excitation With the NI 9237 Module to understand more about the wiring of the external excitation according to the connector type of your NI-9237 (Dsub or RJ-50) and some additional considerations.