LVDT

[Cuchito]

hola alguien como debe calibrarse un LVDT para usarlo en nimax con un nidaq ?

el lvdt es de +-7,5 mm con un vex 3 volt y una sensibilidad de 83mv/V

[GerdW]

Hi Cuchito,

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@Cuchito wrote:

Hello, someone, how should an LVDT be calibrated to use in nimax with a nidaq?

the lvdt is +-7.5 mm with a vex 3 volt and a sensitivity of 83mv/V

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"Calibration" is independent of the DAQ devices you want to use your sensor with…

Are you (still) using NI-DAQ (traditional) or do you use NI-DAQmx ("modern" API since 10+ years)?

Which DAQ device do you use?

[Henrik_Volkers]

Calibration of an LVDT will need:

- A reference distance representation (say some gage blocks, µm-screw,... ) calibrated of course 😉

- A sine source (3V in your case ) capable to drive the LVDT load.  Signalgenerators (say an analog output of a DAQ-card) often can't provide the current needed. So maybe an amplifier is needed (Could be an mono audio amplifier 😉 )

- I would use a two channel symultanious (!) DAQ (ADC) unit to capture excitation and LDVT output. And if you want to do a qualified calibration, the ADC unit migth/will need a calibration too.

- Some software to read both channels , calculate amplitudes and phase(for the sign)  and the ratio.

  (Your information is not really complete, the sensitivity is usually xx (mV/V)/(length unit, say mm) 😉 )

You can start programming using the soundcard 🙂  the Headphone driver should be able to drive the LVDT, but you need one or two voltage deviders for the line input

Using the tone detection vi (extract tone vi) can run into problems if the LVDT output is about zero, since the frequency is known, better use 3 parameter linear sine approximation on both channels. If the resulting frequencies of the extract tone vi isn't the same the result is questionable.

If you use the soundcard (usually 24 bit ) the dynamic range and linearity should be sufficient to use the same range vor excitation and LVDT output. If you measure twice with swapped channels and calculate the complex geometric mean, the gain and phase errors of the soundcard cancels and no ADC calibration is needed... (Needs some standing in an audit 😄 )  ... but still leaves the nonlinearity as error source.