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FDC2214EVM: How to design a sensor for my application using FDC2214EVM

Henry3374
Prodigy 190 points
Part Number: FDC2214EVM

I have a machine and I want to keep the Z head a fixed distance above the material as I move the Z head in the XY plane without touching the surface.

I've successfully done this using a LDC1000 and a coil for metal objects eg if I move the head up then the LDC1000 gives me a reliable reading difference so I am able to maintain a position of say 1mm above the surface at all times even if the surface is curved or bowed.  In this case, I wrapped a coil and the inductor coil was the sensor.

I want to do the same thing but make it work for both metallic and non-metallic objects so look to the FDC2214EVM.

However, I am a bit confused how to make this work.  The idea I understand is there are two pins that form two plates eg a ground plate and a sensor plate.  On the EVM, the sensor plate is a copper pad on the PCB bu the ground is disconnected?  Why is the ground disconnected eg where is the second plate?

For my application, can I use any metal object as the sensor eg can I use a metal cone or rod does it have to be a flat plate?  

Do I just leave the ground disconnected or should I connect it to the machine body?  The machine body is all metal and the surface I'm trying to detect sits inside the machine.  If the object is conductive, do I need to insulate the object from the machine body otherwise wouldn't it just be grounded to the rest of the machine and undetectable?

Thank you for any suggestions.

  • 0
    TI__Genius 17440 points

    Hello,

    In general, the sensor electrodes form one half of a parallel plate capacitor. The other half is formed by the target object (NOT one of the INxA/B pins). In some cases this object is connected directly to ground, and in some cases this object is indirectly grounded. 

    The electrode can be any shape, and its sensing distance is based on its surface area. If your target is metal, I do recommend grounding it. This will increase the capacitance and sensitivity between the sensor electrode and the target. If you have a large grounded object near your target (like the machine body), then your sensitivity to the target will decrease. It would be best to insulate the target from the machine body.

    Best Regards,