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CCS/FDC2212: FDC2212 capacitive measurement value problem ??

ufukv
Prodigy 110 points
Part Number: FDC2212
Other Parts Discussed in Thread: FDC2214

Tool/software: Code Composer Studio

Hi dear developers,

I am using FDC2212. Measurument result:

Maximum distance capacity value : 120pF

Minimum distance capacity value : 121 pF

Parasitic value : 50-100 fF

Measurement resolution requirement is 1 ms. I am calibrating 10 sample in this range. While it's not possible 1pF (1000 fF ) capacitance difference. How can you help ? Thank you for helps.

  • 0
    Prodigy 110 points

    Is it possible to accurately measure a capacitive sensor that has a large dynamic range (~120pf to ~130 pf)?  How can you help ? Thank you for helps.

  • 0 in reply to ufukv
    TI__Genius 17440 points

    Hello,

    Can you clarify what you mean by "1ms" resolution? Typically we define resolution in terms of distance or capacitance steps.

    The FDC2212 can measure 10pF shifts in capacitance without difficulty. Can you clarify what you need help with?

    Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 110 points

    It is mean, I want to read 1000 pieces of data per second for distance. It is my sistem restirictions.(1 Khz or more)

    My main aim is increase shifting capacitance or decreasing parasitic capacitance. Why I can not measure 10 pF shifting ?

    I using moving average filter and kalman filter for decreasing parasitic capacitance, but distance conversion time is increasing too.

    1 - I can not implement more filter in my code  but sistem is sloving down. Is there any other software solution ?

    2 - The hardware amplifier and/or hardware filter necessary ?

  • 0 in reply to ufukv
    TI__Genius 17440 points

    Hello,

    One way to increase your capacitive response is to ground your target. Another option is to increase the size of your sensor. Increasing the size of your target will also help, though this is not possible for some applications.

    If you are already using a moving average algorithm, you may find this derivative integration algorithm for proximity sensing useful.  

    It's not necessary and not recommended to use a hardware filter. The LC tank is inherently a narrow bandpass filter and does not need additional filtering for noise immunity. Hardware filtering could interfere with the FDC2214's ability to drive the sensor.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 110 points

    Hi Kristin,

    I will consider your advice. This documents is awesome. Seems to be useful.

    Thank you.