Q: What are ultrasonic sensors?
A: Ultrasonic sensors are industrial control devices that use sound waves above 20,000 Hz, beyond the range of human hearing, to measure and calculate distance from the sensor to a specified target object.
Q: How does an ultrasonic sensor work?
A: The sensor has a ceramic transducer that vibrates when electrical energy is applied to it. The vibrations compress and expand air molecules in waves from the sensor face to a target object. A transducer both transmits and receives sound. The ultrasonic sensor will measure distance by emitting a sound wave and then "listening" for a set period of time, allowing for the return echo of the sound wave bouncing off the target, before retransmitting.
Q: When would I use an ultrasonic?
A: Because ultrasonic sensors use sound rather than light for detection, they work in applications where photoelectric sensors may not. Ultrasonics are a great solution for clear object detection and for liquid level measurement, applications that photoelectrics struggle with because of target translucence. Target color and/or reflectivity don't affect ultrasonic sensors which can operate reliably in high-glare environments.
Q: So why wouldn't I just use an ultrasonic, instead of an optical sensor?
A: Ultrasonics definitely have advantages when sensing clear objects, liquid level or highly reflective or metallic surfaces. Ultrasonics also function well in wet environments where as an optical beam may refract off the water droplets. However, ultrasonics are susceptible to temperature fluctuations or wind. With optical sensors, you can also have a small spot size, fast response and in some instances, you can project a visible spot on a target to help with sensor alignment.
Q: How do ultrasonic sensors deal with noise and interference?
A: Any acoustic noise at the frequency to which the ultrasonic sensor is receptive, may interfere with that sensor's output. This includes high-pitched noises such as those created by a whistle, the hissing of relief valves, compressed air or pneumatic devices. You might also get acoustical crosstalk by locating two ultrasonics of the same frequency close together. Another kind of noise, electrical noise is not exclusive to ultrasonic sensors.
Q: What environmental conditions affect an ultrasonic sensor?
A: The speed of an ultrasonic sensor's sound waves are affected by temperature fluctuation. As temperature increases, the sound waves travel faster to and from the target. While the target may not have shifted, it will seem to the sensor that the target is closer.
Air currents due to pneumatic equipment or fans may also deflect or disturb the path of the ultrasonic wave. This could lead a sensor to fail to recognize the correct location of a target.