The S18UBA from Banner Engineering is an Ultrasonic Sensor with discrete output and TEACH-Mode programming. The U-GAGE™ S18U series sensor emit one or multiple pulses of ultrasonic energy, which travel through the air at the speed of sound. A portion of this energy reflects off the target and travels back to the sensor. The sensor measures the total time required for the energy to reach the target and return to the sensor. To improve accuracy, an ultrasonic sensor may average the results of several pulses before outputting a new value. The speed of sound is dependent upon the composition, pressure and temperature of the gas in which it is travelling. For most ultrasonic applications, the composition and pressure of the gas are relatively fixed, while the temperature may fluctuate.