AD7747 Differential Mode


I want to detect objects between two closing doors with the AD7747.

The Sensor consists of two pair of electrodes, which are one after the other. One pair of electrodes will sit on the top closing area and the other pair on the bottom closing area of the door.

I want to use the AD 7747 with the differential mode. In theory, there will be capacitance changes, when there is an object converging to one of the two electrodes.

My questions are:

  • What will be the output data of the AD7747? Will it be the difference (data = Cx – Cy)? So if no object is in the field of both electrodes. The difference will be zero.
  • Is it possible to extent the measuring wires to the electrodes? E.g use of a coax cable with the shield signal on the coax cable shield? Because of the need of two exactly symmetrical electrodes and not symmetry sitting AD7747 in the door.

Thank you very much for your help!!


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