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FDC2114: detect the capacitance between the two metal plates

Amy Luo
Expert 6895 points
Part Number: FDC2114
Other Parts Discussed in Thread: FDC2214

Hi team,

One of our customers needs to detect a variable capacitance consisting of two metal plates:

The two metal plates are parallel to each other and the distance is constant, and the upper metal plate moves horizontally to cause the two metal plates to change their area opposite, causing a change in capacitance value, which the customer wants to detect. The capacitance value range is 0~6pF.

Can it be implemented using FDC2114, and if not, are there any other recommendations?

Best Regards,

Amy Luo

  • +1
    TI__Mastermind 18545 points

    Hello Amy, 

    That capacitive change is within the operating range for the FDC2114. What is the resolution requirement for this? If they need to detect very small increments of change, they may want to consider the FDC2214 instead of the FDC2114 due to a higher resolution on the output. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Expert 6895 points

    Hi Justin,

    Thank you for your reply.

    However, I see the following link FAQ about FDC2X1X (screenshot below) that states that such sensor cannot be used for Metal detection. Please confirm again whether it can detect metal, or for what reason this FAQ makes this conclusion

    https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/976712/faq-fdc2x1x-capacitive-sensing-faqs

    If FDC2X1X  can measure, can the following wiring method be used? One metal plate as sensor and the other as target object

    Best Regards, 

    Amy Luo

  • 0 in reply to Amy Luo
    TI__Mastermind 18545 points

    Hello Amy,  

    It is within range of the device but inductive sensing approaches tend to work better so they are generally preferred. In inductive sensing approach, the sensor plate would be replaced by an inductive coil. The design of the coil would depend on the requirements of the overall system requirements. Would this be a detection (on/off) type application? Would the customer need to determine the position of the metal plate? Also, what is the size of the moving metal plate? 

    Best Regards, 

    Justin Beigel