Measuring water levels in tanks or on rivers using radar has always been very expensive. Though in recent years prices of these types of radars have come down, the HLK-LD2413 24GHz is in a completely different league. With a price around €10, and the promise of millimeter accuracy it is almost too good to be true.
Unfortunately the documentation on these HLK sensors is often limited, and if it is present it is still hard to get them going. This is my attempt to get the sensor working as a stand-alone instrument.