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LDC1101: Repurpose the LDC1101 for use with Capacitive Probes

Joe Leonard
Prodigy 40 points
Part Number: LDC1101

Hello,

Is it possible to form the resonant LC section with capacitive probe and a fixed inductor or some coax . The resonant frequency would be modulated with the change in capacitance rather than inductance, the LDC1101 wouldn't know any better. 

Looking at your Capacitance to Digital portfolio none of them sample quite as quick as the LDC1101, so this would be an advantage in some scenarios. 

Any guidance on this would be appreciated.

Cheers,

Joe

  • 0
    TI__Mastermind 40295 points

    Joe,

    Thank you for your inquiry and your interest in TI products.

    In theory, your proposal would work, but please understand we have no experience with these devices being used in an active probe application.

    The device looks only at the change in the resonant frequency, so changing the capacitance will bring about that change.
    One of the implications of this is that these devices are better at determining a change in inductance, as opposed to a total inductance, like an LCR meter would provide. Measuring total inductance/capacitance will most likely require a careful calibration customized for your application. 

    Also, if you plan to use the switched output in your application, the settings of registers L_THRESH_HI/LOW_LSB/MSB may be different compared to an inductance measurement. Some of the Rp-oriented measurements & calculations may need to be translated to account for capacitance.

    I hope this helps. 

    Regards,
    John