We want to measure differential level across our travelling band filters to monitor the condition of the filters and control the speed accordingly. These screens are installed at sea water intake and previously installed bubbler system does not work properly. Now we want to install non-contact type (Ultrasonic) sensors to monitor differential level across screens and manage the speed of screen. We will appreciate if somebody who is already using ultrasonic sensors with digital output (relay activation) for such application share his/her experience with us. What make of sensors and transmitters are used and how they are performing?