Guided Wave Radar Level Transmitter is thekind of measuring instrument that is based on the principle of time travel.  The radar wave travels at the speed of light,and its running time can be converted into a level signal by the electroniccomponents.  The probe emitshigh-frequency pulses which spread along the cable, and the pulses arereflected back when they encounter the material surface and received by thereceiver inside the meter.  The distancesignal is then converted to the level signal.