HBDF is an intelligent sensor with a built-in microprocessor. It is designed to measure ice formation on evaporators(Air-Coolers). It emits a 4-20 mA signal. Apart from the 4-20 mA signal, the sensor also has built-in relays for start/stop defrost and external temperature sensor for measuring when the ice is melted.Product Features:Defrost starts only when needed (on demand)Stop the defrost when ice is melted (input from temperature sensor located on evaporator surface)Save energy compared with timer based defrostingGain more capacity - fewer and shorter defrost cyclesEasy installation - also on existing sites