Thanks for the reference on the FDC1004 – there is an App Report
Capacitive-Based Liquid Level Sensing Sensor Reference Design
I’ve attempted some custom PCB electrode for measuring water depth. The discussion is excellent. The challenge is field calibration – if looking for a 0-1m (for example) change – how to know when installing in the field and measuring capacitance, that the specific numbers being measured represent 1m of length.
The reference electrode design is a bit un-wieldy – but useful for discussion and experimentation.
The holy grail is a simple wire.
I found some unusual properties of the capacitive field.
I had the Aquaplumb in a column (3″/8cm dia pipe) of water, and varied the height.
I got useful readings. However, even with a full pipe – the wire in a reasonably large volume of water, when I brought my hand (a relatively small volume of water) to about 10-30cm away, it did cause an effect on the reading. The only explanation I had was there was a really extended field effect, but something really interesting.
From the reference design idea – perhaps some aluminium (or copper) tape could be used.