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Fdc2212, Capacitance to Digital

Geoffrey Probert62
Prodigy 10 points
Other Parts Discussed in Thread: FDC2212, TIDA-00509

I would very much like to use the new FDC2212 to measure capacitance. I want to measure the capacitance of a coax cable connected to ultrasound piezo. Probes in the medical arena have up to 256 of these in a single bundle. We have high voltage switch to select a single coax. By comparing the capacitance of all of the cables, we can find broken ones. Section 10.3 of your data sheet says "The FDC does not support hot-swapping of the sensors. Do not hot-swap sensors, for example by using external multiplexers." What are the issues in doing this? Can this be done if I sample at a slower rate? Other than this issue, the FDC2212 looks to be ideal fro my application.

  • 0
    TI__Guru* 93715 points
    Geoffrey,


    I've moved this post to the Capacitive Sensing Forum. You should be able to get an answer here.


    Joseph Wu
  • 0
    TI__Expert 7400 points

    Hi Geoffrey:

    It is possible to use external multiplexers. When it mentions that it does not support hot-swapping, that means, that the device cannot be driving the waveform when the multiplexers are switched. If that happens, the device could get damaged. To get an idea of how multiplexers can be implemented, please see TIDA-00509. This reference design is based on our LDC, inductive technology, of which the FDC2212 uses a similar architecture.

    Thanks

    -David Wang

    Capacitive Sensing Applications

  • 0 in reply to David Wang11
    Prodigy 20 points
    hi Dvid Wang11!
    i'm using FDC2212 for own our application to mesure oil level, but when i read data from FDC2212 and convert to capacitance follow equations 7 and 9 in datasheet FDC2212(page 19) the capacitance value not linear. any my mistakes?
  • 0 in reply to Quang Nguyen
    TI__Expert 7400 points

    Would it be possible to show me the data that you obtained? I would like to see what it looks like from empty to max at each unit level height.

    Also next time, please post in a new thread if you have a specific question on an application.

    Thanks

    -David Wang

    Capacitive Sensing Applications

  • 0 in reply to David Wang11
    Prodigy 20 points
    Hi David Wang,
    thank you for your reply, can i have your email?, my email: quang.nguyen@lisatech.vn that we can easy for communicate with you. waiting for your reply!