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AD7147 Theory of Operation

Question asked by creilly on Feb 3, 2014
Latest reply on Feb 11, 2014 by DarraghCorrigan

I would like to better understand how the AD7147 actually works and was wondering if someone could help answer some questions. I understand that the chip switches between exciting the CINx electrodes with the 250kHz signal and measuring the capacitance. However, how is the capacitance measured (charge, current, etc.)? Also, is the capacitance that is measured the electrode's self capacitance or a mutual capacitance? Lastly, does the interacting conductor need to be "grounded" or can it be floating? More specifically, would accurate detection work with a floating silicon chip acting as the the second capacitor plate instead of a finger that is grounded?