The Turbimax CUS71D from Endress+Hauser Inc., Greenwood, IN, is an ultrasonic immersion sensor for interface measurements in processes where suspensions are separated into their liquid and solid components by sedimentation. The sensor can continuously monitor the separation and transition zones of the clarification and settling phases. It uses a piezoelectric crystal to generate an ultrasonic signal and measures the time required for the signal to reach solid particles in the separation zone and then return to the receiver. Each model can detect the interface level at distances of 1–32 ft. from the sensor; max. error is 1.3 in. Two models are available: a standard sensor and a sensor with a wiper to avoid film and air bubble formation at the transducer.