The SR50AH heated sonic distance sensor provides a non-contact method for determining snow or water depth. It determines depth by emitting an ultrasonic pulse and then measuring the elapsed time between the emission and return of the pulse. An air temperature measurement is required to correct for variations of the speed of sound in air. The SR50AH includes an integrated heater that prevents ice and rime from coating the transducer. Note: Campbell Scientific recommends model SR50A-316SS-L for marine environments.