NI 9237

[0206]

Hello.

I want to use the cDAQ with NI 9237 to measure strain.

From what I read the NI9237 has two internal resistors to complete the bridge. Are the values of these resistors constant or are the values configurable by software?

I think this is important in order to choose the best extensometers. By picking the right values I can maintain the bridge in equilibrium for zero strain (R1/R2=R4/R3).

Onother question is related with the type of connection to NI9237. The place I want to mount the extensometers will be far from cDAQ. Is the remote sensing configuration the best way to compensate the cables lenght?

Kind Regards,

Daniel

[Audrey_P]

Hi Daniel,

First, thank you for using the National Instruments discussion forum.

Generally knowing the nominal resistance of the completion resistor is not useful: the most important to know, is that they have the same value (10Kohm) and provide a stable reference voltage of Vex/2 (with Vex, the excitation voltage).

Here are two documents which can help you:
Why is there No Nominal Resistance Specification for NI 9237?
Connecting Strain Gauges and Shunt Resistors to the NI 9237

In order to respond to your second question, the remote sensing is a way to correct for errors in excitation leads, so it is the configuration to choose when the wire are long. It has to be notes that it is generally most appropriate for half- and full-bridge sensors.

Best regards,