What is a sensor, how does it work, and what are the various types of sensors?

A sensor is a device that has been designed to sense or comprehend physical phenomena and produce an output signal based on what it senses. It can be used as a machine or a subsystem that can detect any change in its environment and send the data to other electronic devices, such as computer processors.

How does a sensor work?

Sensors work by detecting physical changes in the device’s environment and output them as analogue voltages or digital signals. This is then sent to a human-readable display where it can be monitored or transmitted, or relayed to other electronic devices for further processing.

A electronic sensor is usually equipped to be able to pick up the slightest change in its surroundings and instantaneously relay the information for processing. The higher the sensitivity of the sensor, the better it is.

Different types of sensors and sensor applications

Depending on their mechanism and application, sensors can be of several different types, including:

• Photoelectric Sensors
• It is an electronic device that can measure the distance to, as well as the presence or absence of, an object. Photoelectric sensors use an infrared light transmitter and a photoelectric receiver that can receive the reflected infrared light back to do its job. This infrared light can then be measured, interpreted, or relayed to other electronic devices for processing and monitoring.
• Depending on the model of the sensor used, photoelectric sensors can also use ultraviolet light to detect luminous objects, as well as visible red or green light to read colour marking, or even red laser to detect long distances or short focal lengths.
• Some of the advantages of using photoelectric sensors include:
• - Easy long-distance measuring
• - Greater resistance to environmental hazards like dust and grime which cannot hamper the accuracy of the readings
• - Precise detection with high repeat accuracy
• - Detection does not depend on the colour of the targeted object or its angular position

• Proximity Sensors
• Proximity sensors are devised to be able to detect the presence of a physical object within its vicinity without the requirement of any physical contact. It works by emitting an electromagnetic field of radiation within its range, and the presence of a physical object in the proximity is detected and returned to the sensor.

• Inductive and Capacitative Sensors
• Inductive proximity sensors are particularly designed to be able to detect metal objects as big as 60 mm. The inductive proximity sensor is equipped with an oscillator with a sensing face on its windings. The winding generates an alternating magnetic field which can be used to detect metal objects within the magnetic field. The resulting currents that are induced by the metallic object can be picked up by the sensor.
• Capacitative sensors, on the other hand, are non-contact devices that can detect any object of 20mm size, irrespective of its material or conductivity. Capacitative sensors apply voltage in an area and measure the change in the electrical properties to detect objects. It relies on the principle of capacitance, or an object's innate ability to hold or retain an electric charge.

• Ultrasonic Sensors
• An ultrasonic sensor is designed to measure the distance between the sensor and a targeted object with the help of ultrasonic sound wave emissions.
• An ultrasonic sensor is equipped with a transmitter that uses piezoelectric crystals to produce and emit sound waves and a receiver to intercept any sound wave reflections. The sound reflected back from the targeted object is received and converted to digital or electronic signals that can be later interpreted or processed.

• Pressure Sensors
• Pressure sensors function as detection devices used for measuring the pressure of liquids and gases. The pressure sensor works on the principle of force per unit area and usually serves as a transducer - it generates and records signals when pressure is applied.

You can easily get all the above-listed different kinds of sensors on the Schneider Electric eShop.

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