I recently purchased two of the Grove capacitive water sensors https://wiki.seeedstudio.com/Grove-Water-Level-Sensor/ I will use them to measure the amount of water in a small tank used for watering plants.
Upon testing they work great, but when you unpower the device and then power it again - the sensor returns zero. The device is working and responding to I2C calls, but it is not returning the correct value. To make it work, I have to take the sensor out of the tank, wipe it with a dry cloth and then it will start measuring correctly.
Both the sensors I purchased work exactly the same. If I unpower them, they no longer show the correct value.
This basically makes the sensor useless to me and for anyone that had hoped to build this into an unattended system? Did you not test this before starting to sell it?