Review on Ultrasonic Water Tank Liquid Depth Level Meter Sensor: High/Low Alarm, Temperature Display, 3.3 Inch LED by Charles Dean

This unit works fine but there is a problem with the controller and the minimum allowable air gap between the top of the maximum water level and the sensor. Not many tanks I know have a big gap. This device requires quite a bit of clearance and is therefore not accurate when the tank is full as you cannot set it to the actual level. There's also no calibration, so you can tweak the settings a bit to be more accurate.