Can I Read Raw Measurement Voltages Between Coils on the PXIe-4340?

Updated Nov 30, 2023

Reported In

Hardware

  • PXIe-4340

Software

  • LabVIEW Professional

Driver

  • NI-DAQmx

Issue Details

I have a 5-wire connection to an LVDT. Can I read the (AI+ to CT) and (AI- to CT) voltages from the PXIe-4340 in NI-DAQmx using LabVIEW?

Solution

There is no way to obtain the values of the raw voltages between the two coils in LabVIEW. Our driver will calculate and return position values when you use an LVDT DAQmx task.

In some cases, you may be able to gather the information needed by working backwards through the equation that provides displacement. Note, even when connected in a 5-wire or 6-wire configuration, the PXIe-4340 always uses the displacement equation for a 4-wire configuration because the center tap wires are  not utilized by the PXIe-4340. The equation is as follows:
D = (V1 - V2)/(Vex * Sensitivity)
 
D is the displacement, V1 and V2 are measured at the LVDT, and Vex is the excitation voltage.

Additional Information

For a 5-wire LVDT/RVDT you need to recalculate the sensitivity,if not you are going to get the wrong measurements.

To recalculate the sensitivity follow the equation below:

                                                                                                Sensitivity = (V1 - V2) / (Vex* D)


D is the displacement in degrees, V1 and V2 are measured at the LVDT, and Vex is the excitation voltage

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