EVAL-AD7746LDZ - Ground electrode connected to liquid

Q

I read your article „Liquid Level Sensing Using Capacitive-to-Digital
Converters“ and I’m interested in this form of level sensing. We received the
EVAL-AD7746LDZ to make tests. But we have a question regarding the realization
of the sensor.

Can you please explain, why you use a ground plane connected to the liquid? Is
the liquid connection really necessary for the usage of the sensor? Did you try
it without this connection?

A

The external ground electrode connected to the liquid was added to improve the
overall performance and linearity of the sensor as the liquid moves up/down the
sensor.
If the ground is not common to the water then the water becomes part of the
sensor excitation signal and if i.e. a person touches the container the data
output can change. So, adding in the external ground stopped interference if
someone came into contact with the test system.

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