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EZ430RF2500(MSP430) under wet environment

Xu Meng
Prodigy 50 points

Dear,

I am using EZ430RF2500 Demo to monitor pressure information under wet environment. 

A MEMS capacitance sensor connectted to the board through the wire.

The measurement done by charging and discharging the capacitance. 

The prototype works well in air but not in water even the device is coated well by different water resistance materials.

Also I am seeing a capacitance reading increased by the function of time. 

Dose anything I miss regarding the MSP430?

Thanks

Xu

 

  • 0
    Prodigy 50 points

    This is how I measure.

    Capcitance -> Charging Time -> Internal Clock Cycle(Counts)

    I have the other fixed cap -> Counts too.

    Then Sensor Counts -> real capaciance.

     

  • 0 in reply to Xu Meng
    Guru 12160 points

    Hi Xu Meng,

    Are you considering temperature in your measurements?  Both the capacitive pressure sensor and the "fixed" reference cap probably have temperature coefficients.  Not sure which parts you are submerging, but they change temperature over time while submerged to match the water temperature.

    Just a thought.

    Jeff

  • 0 in reply to Jeff Tenney
    Prodigy 50 points

    Hey Jeff,

    Thanks for your input. 

    Actually, it was submerged in the water bath around 37 C degree.

    The internal temperature sensor of MSP430 indicate the temp was fixed.

    I did the whole submerge and only sensor submerged. 

    So far, my circuit works in air but not water. Try several times and different water proof. Crazy Glue, silicon, dielectircal liquid tape.

    Xu

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