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Capacitance I/O vs. CapTIvate

stenzer
Prodigy 210 points


Hi,

I'm looking for an MCU including a capacitance to digital converter like a single IC solution of Analog Devices (e.g. AD7745). It seems the mutual capacitance measurement provided by the CapTIvate technology has the same principle, with an excitation source and a receiver. Unfortunatly I have not found a proper document with technical specifications. Especially if the capacitance is profided by means of a digital coded value. Or is the detection of an object (e.g. finger) just represented by a single high or low level.

Furthermore I'm interested in the working principle e.g. which kind of excitation is used (sine- ore square wave) and how is the capacitance change evaluated (e.g. resonance circuit) .

BR

  • 0
    TI__Mastermind 25045 points
    Hi stenzer,

    We are looking into the matter and trying to get your request to the right team. We will get back to you in time.

    Regards,

    David
  • 0 in reply to DavidL
    TI__Expert 7535 points

    Stenzer,

    Have you seen the CapTIvate Technology Guide?  This is a web-based documentation resource for CapTIvate.

    The Capacitive Sensing Basics chapter introduces the equivilent circuits for self and mutual capacitance, and the Technology section introduces the operational principles of the CapTIvate technology.

    CapTIvate is a relative measurement technology- it measures changes in capacitance over time, but not absolute capacitance.  Capacitive touch and proximity sensing applicaitons do not require absolute capacitance capability, as the variable of interest is the rate of change of capacitance over time.  If you need to measure absolute capacitance, CapTIvate may or may not be ideal depending on your use-case.  What are you looking to do in your applicaiton?  Is this a touch sensing application, or some other use-case?

    CapTIvate measurements are controlled and interpreted by the CapTIvate Software Library (which is also described in the tech guide).  You can have access to processed outputs (touch versus no touch) or raw data that is representitive of the capacitance measured.

    Best regards,

    Walter

  • 0 in reply to Walter Schnoor
    Prodigy 210 points

    Hi Walter,


    thank you for the link.

    For my proposed system I do not need an absolute capacitance value. I just wanna detect capacitance changes. Nevertehless a quantitative capacitance change should be detectable e.g. 25% of the maximal detectable capacitance value. Thus it is important for me to know how long the CapTIvate technology needs to detect a change and also what's the minimal and maximal detectable change is.


    Furthermore, if its possible I want to use an external frequency excitation source (e.g. DDS) to be as flexible as possible.

    I will take a deeper look at the posted link tomorrow.

    Thank you!

  • 0 in reply to stenzer
    TI__Mastermind 25045 points
    I'm marking the thread closed due to inactivity, but you can always use "reject answer" or simply post back to re-open it if you need more help on this issue.

    Regards,

    David

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