Introduction to Proximity Sensors
In the modern world of industry, with automation taking over a number of tasks, a number of important systems are in place to make sure that accidents are kept to a minimum. One such system is the proximity sensor.
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Proximity Sensor
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A proximity sensor is a device that detects objects without physically contacting them. The detection is achieved using an electromagnetic field or beam emitted from the sensor that detects changes in that field.
Types of Proximity Sensors
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Proximity sensors come in a variety of types. Popular types of proximity sensors include inductive, capacitive, ultrasonic and photoelectric.
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Inductive and Capacitive Sensors
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Inductive sensors have an oscillator at the input side, which detects electrically conductive substances like metal based on resistance to the signal the oscillator emits. Capacitive sensors use a detecting electrode and ground electrode to detect a change in the frequency emitted by an oscillator. This frequency change is then compared to a predetermined threshold, which indicates a nearby object when exceeded.
Ultrasonic Sensors
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Ultrasonic sensors use a transducer to produce ultrasonic signals, which are rebounded by objects in the detection area. These rebounded signals are picked back up by the sensor to indicate an object in the area, much like a sonar system.
Photoelectric Sensors
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Photoelectric sensors project light in the detection area and receive back light reflected or transmitted from the object.
Applications
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Proximity sensors are commonly used in almost every facet of automated industry. There are robotic arms that can detect material in their work area, buildings with automatic doors, and consumer electronics, such as Apple's iPhone, which turns off the keypad when it detects the user's ear near the screen.
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