The Basics of Three Types of Ultrasonic Sensors
Ultrasonic sensors are valuable components of modern automated production processes. These sensors use sound waves to detect the presence or absence of objects and are thereby not affected by color or transparency and little by texture. These properties make them ideal for a variety of problem-solving applications. Dittman & Greer supplies customers with three basic types of ultrasonic sensors: diffuse proximity, retro-reflective and through-beam.
Ultrasonic diffuse proximity sensors
These sensors employ a special sonic transducer, which allows for alternate transmission and reception of sound waves. The transducer emits a series of sonic pulses and then “listens” for their return as they are reflected from the target. Once the reflected signal is received, the sensor signals an output to a control device such as a PLC.
These sensors are capable of reliably detecting a variety of targets, including solids, liquids, granules or powders, irrespective of color and opacity, at sensing ranges up to 2.5 m. Their sensitivity, defined as the time window for “listen” cycles versus “send” cycles, may be adjusted via a teach-in button or a potentiometer. While standard diffuse ultrasonics will give simple presence/absence of target information, analog versions provide for actual distance measuring, by offering a 4-20 mA or 1-1- V output dependent on range to the target. This output can easily be converted into useable distance information.
Ultrasonic retro-reflective sensors
Retro-reflective sensors detect objects within a specified sensing distance by measuring propagation time. The sensor emits a series of sonic pulses that bounce off of a fixed opposing “reflector.” The reflector can be any flat, hard surface such as a piece of machinery or board. The sound waves must return to the sensor within a fixed user-adjusted time interval. The sensor signals an output if that time interval changes due to an obstructing object in its sensing path. Since the sensor is, in essence, “listening” for any change in propagation time, as opposed to a returned signal, it is ideal for the detection of sound absorbent and sound deflecting materials like cotton, foam, cloth and foam rubber.
Ultrasonic through-beam sensors
Unlike proximity and retro-reflective sensors, these sensors separate the emitter and the receiver into separate housings. The emitter sends a continuous signal, which is then picked up by the receiver. When an object disrupts the sonic beam, the receiver reacts and triggers an output. These sensors are ideal in applications that require the detection of a continuous object such as a web of clear plastic. If the clear plastic breaks, the output of the sensors will trigger the attached PLC or load.
We at Dittman & Greer would be happy to recommend an ultrasonic sensor for dependable service in your specific application. Please contact us to discuss your requirements.
( From Internet)