Radar transmitters use high-frequency electromagnetic waves and are best for liquids that are tricky to measure because they work even if there’s condensation, foam, or other difficult conditions. They also measure the level of liquids with solids and small solids. In addition to the traditional 4-20 mA output, these transmitters can also send measurements to your Android smartphone or tablet using Bluetooth. There’s an app you can use to set up your transmitter and calibrate it for your system.