An ultrasonic proximity sensor uses a piezoelectric transducer to send and detect sound waves. Transducer generate high frequency sound waves and evaluate the echo by the detector which is received back after reflecting off the target. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to the target. When the target enters the operating range the output switches. The ultrasonic proximity switches are equipped with temperature sensors and a compensation circuit, in order to be able to compensate for changes in operating distance caused by temperature fluctuations. The ultrasonic sensor can work in diffuse, reflex or thru-beam mode.
Thru-Beam: In this case the emitter and detector are 2 separate units. The emitter emits the light which is detected by the detector. A target is detected when it passes in-between the emitter and detector.
Diffuse Reflective: In this case the emitter and detector are put in the single package in such a way that their field of view cross. Here the emitter continuously emits the light. When the target comes within the operating range of the sensor the light from the emitter is reflected off the target and detected by the detector. Retro-Reflective: the main components of this sensor are the emitter, detector and the Retro-reflector. The emitter and the detector are in the same package. The Retro-reflector is placed little far from the sensor. The light from the emitter is reflected off the Retro-reflector and detected by the detector. When the target passes between the sensor and the Retro-reflector the beam is not reflected back to the detector. Here the problem can be that the beam could reflect from the target itself. For this the polarising filter is used in the sensor. Hence only the light reflected by the retro-reflector is detected by detector
The advantages of an Ultrasonic proximity sensor are
No physical contact with the object to be detected, therefore, no friction and wear
Unlimited operating cycles since there is no mechanical contact with the target
Ultrasonic proximity sensors are not affected by target colour or atmospheric dust, snow, rain..etc
Can work in adverse conditions
Sensing distance is more compared to inductive or capacitive proximity sensors
The targets to be detected can be in the solid, liquid, granular or powder state.
The application of ultrasonic proximity sensor is
Ultrasonic proximity sensors use reflected or transmitted ultrasonic waves to detect the presence or absence of a target component. The output is boolean, that is, the sensor merely detects whether the target is or is not within the detection range.
Ultrasonic proximity sensors emit and receive sound waves. The carrier signal is a high frequency, inaudible sound wave. They detect the presence of the target object in one of two configurations.
Diffuse or Reflective sensors have the transmitter and receiver packaged in the same housing. When a target enters the sensing range of the device, the ultrasonic waves are reflected back to the sensor.
There are a number of features that may be important to consider when selecting ultrasonic proximity sensors.
Field adjustable sensors are required when adjustments need to be made while the proximity sensor is in use. Potentiometers are commonly used to control the detection range.
Self-teaching proximity sensors can be auto-calibrated to trigger the switch at a specific target location.
Materials of construction and enclosure ratings must be considered when the sensor will be located outdoors or exposed to extreme temperatures, or under the influence of wet, humid, dusty, dirty or corrosive process conditions.
There are two types of ultrasonic sensors. Proximity Detection: An object passing within the preset range will be detected and generate an output signal. The detect point is independent of target size, material or reflectivity.
Distance Measurement Sensor Applications. Senix ToughSonic® Ultrasonic Sensors measure the distance of target objects or materials through the air using “non-contact” technology. They measure distance without damage and are easy to use and reliable. Whether used indoors or out, ToughSonic® sensors can take abuse.
An Ultrasonic sensor is a device that can measure the distance to an object by using sound waves. It measures distance by sending out a sound wave at a specific frequency and listening for that sound wave to bounce back.
Ultrasonic sensors “are based on the measurement of the properties of acoustic waves with frequencies above the human audible range,” often at roughly 40 kHz 1). They typically operate by generating a high-frequency pulse of sound, and then receiving and evaluating the properties of the echo pulse