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Shielding Inputs From Stray Capacitance (General Advice)

Question asked by Dave_Tripp on Jul 12, 2016
Latest reply on Jul 14, 2016 by Dave_Tripp

Hi,

 

I'm using an AD7147 as a force sensor on a PCB, connected to the AD7147 evaluation board right now. I have two metal pads on my PCB that I have placed a square of silicone rubber on to act as a dielectric, with an aluminum square on top connected to ground to act as the other plate in the capacitor. I am having issues though because even though I have connected the top plate to ground, the capacitance values change whenever my hand gets close to the sensor. I'll attach a schematic of my board below, the board I've designed is simply connecting to the edge connector of the evaluation board. I have the AC shield connected to a plane around the sensors.

 

Does anyone know how I can shield my sensors so they are unaffected by the environment around them? Unfortunately the effect of my hand moving within a few cm of the sensor is greater than the effect of the applied force.

 

Thanks,

Dave

 

(I asked this question earlier, sorry, realized I should have used a better title).

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