Hello community,
We have FDC2214EVM module connected to four plates via ~1m long triax cables.
The plates (5cmx5cm) are arranged around the test object as follows: one plate (labeled as "S") is sitting in front of it, one is above ("A"-plate), and two lateral plates on the left and right sides of the object ("L" and "R", respectively).
And we see difference in the device performance i.e. different capacitive signal patterns, depending from day to day when we connect plates to same channels or change plate connection pattern.
For instance, attached below graphs show capacitive signal patterns when we connect plates to same channels (A plate to ch0, S plate to Ch1, R to ch 2 and L to Ch3) on differnt times.
In the given experiment plates are satying stationary and the object is shifted by 1 mm steps away from S plate. As you see, the capacitive change is largest on the channel, connected to S plate, but sometimes we see and sometimes we dontsee capacitive changes on other channels. Similar phenomenon is observed when we change connection pattern.
All triaxes are connected to the FDC2214EVM in the same way: the center conductor of the triax is connected to channel input A, the inner braid is floating and the outer braid is grounded to the device ground.
The channel input B is not used. FDC2214EVM is set to work in differential mode. Single-ended configuration provides the same result.
The voltages on each channel were adjusted and tested with the scope to be ~1.77 V.
Did you have similar experience with the performance variation with cable connection?
Would you please recommend how to rectify it.
Warm regards,
Alex