My application is similar to liquid level monitoring method that described below, pasting the ruler outside the container and monitor the liquid level inside the container.
We build our own the ruler (~5cm x ~2cm and without grounding) and connect 4 wires to EVAL-AD7746EBZ and then showing the capacity and water level on PC software "AD7746 Capacitive Level Sensor Demo v2.2", the result is what we expected but when we build a longer ruler, the capacity value is very unstable and easy to hit the maximum level 4pF when inside have water.
Below are my questions:
1) We keep searching on Engineer Zone, but cannot find any reference circuit about EVAL-AD7746LDZ and any design guideline for the "Ruler" that may fit for our application?
2) Is it possible to calculate / design the PCB traces for measuring over 30 cm of water if just pasting outside the container?
3) Is there any way to adjust the maximum capacity level if keep using the PC software?
Thank and regards,