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EVAL-AD7746LDZ - Ground electrode connected to liquid

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?
 

 

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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