Sharp GP2Y0A21YK IR proximity sensor cropped

A proximity sensor is a

sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an

electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

field or a beam of

electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...

(

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

, for instance), and looks for changes in the

field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

or return

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive proximity sensor or

photoelectric sensor A photoelectric sensor is a device used to determine the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in industrial manufacturing. There are three ...

might be suitable for a plastic target; an inductive proximity sensor always requires a metal target. Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between the sensor and the sensed object. Proximity sensors are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...

s, compressors, and motors that use sleeve-type bearings. A proximity sensor adjusted to a very short range is often used as a

touch switch A touch switch is a type of switch that only has to be touched by an object to operate. It is used in many lamps and wall switches that have a metal exterior as well as on public computer terminals. A touchscreen includes an array of touch switches ...

Use with smartphones and tablet computers

Proximity sensors are commonly used on

mobile device A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physical ...

s. When the target is within nominal range, the device

lock screen A lock screen is a computer user interface element used by various operating systems. They regulate immediate access to a device by requiring the user to perform a certain action in order to receive access, such as entering a password, using a cert ...

user interface will appear, thus emerging from what is known as

sleep mode Sleep mode (or suspend to RAM) is a low power mode for electronic devices such as computers, televisions, and remote controlled devices. These modes save significantly on electrical consumption compared to leaving a device fully on and, upon resu ...

. Once the device has awoken from

, if the proximity sensor's target is still for an extended period of time, the sensor will then ignore it, and the device will eventually revert into

. For example, during a

telephone call A telephone call is a connection over a telephone network A telephone network is a telecommunications network that connects telephones, which allows telephone calls between two or more parties, as well as newer features such as fax and interne ...

, proximity sensors play a role in detecting (and skipping) accidental touchscreen taps when mobiles are held to the ear. Proximity

s can be used to recognise air gestures and hover-manipulations. An array of proximity sensing elements can replace vision-camera or

depth camera Range imaging is the name for a collection of techniques that are used to produce a 2D image showing the distance to points in a scene from a specific point, normally associated with some type of sensor device. The resulting range image has pix ...

based solutions for hand gesture detection. File:BlackBerry Leap-sensores array infrared proximity-dark red PNr°0725.jpg, The pulsing proximity sensor of a

BlackBerry Leap The BlackBerry Leap is a discontinued smartphone developed by BlackBerry Limited. Announced on March 3, 2015, at the Mobile World Congress with initial availability in April 2015, the Leap is a follow-on to the affordable Z3 model with a number ...

File:BlackBerry Leap-sensores array infrared proximity-I6400 VNr°0004.webm, Video of the pulsing proximity sensor of a BlackBerry Leap

Types of sensors

Capacitive A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a c ...

Capacitive displacement sensor Capacitive displacement sensors "are non-contact devices capable of high-resolution measurement of the position and/or change of position of any conductive target".

* Doppler effect (sensor based on doppler effect) * Inductive *

Magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...

, including magnetic proximity fuse * Optical **

Photoelectric The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...

Photocell Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or b ...

(reflective) ** Laser rangefinder ** Passive (such as

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

s) ** Passive thermal

Radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

* Reflection of ionizing radiation *

Sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...

(typically active or passive) *

Ultrasonic sensor Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. They can be divided into three broad categories: transmitters, receivers and transceivers. Transmitters convert electrical signals into ultrasoun ...

Fiber optics An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

sensor *

Hall effect sensor A Hall effect sensor (or simply Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field using the Hall effect. The output voltage of a Hall sensor is directly proportional to the strength of the field. ...

Applications

Parking sensors Parking sensors are proximity sensors for road vehicles designed to alert the driver of obstacles while parking. These systems use either electromagnetic or ultrasonic sensors. Ultrasonic systems These systems feature ultrasonic proximity de ...

, systems mounted on car bumpers that sense distance to nearby cars for parking * Inductive sensors * Ground proximity warning system for aviation safety * Vibration measurements of rotating shafts in machinery * Top dead centre (TDC)/

camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...

sensor in

reciprocating engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...

s. * Sheet break sensing in paper machine. *

Anti-aircraft warfare Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes Surface-to-air m ...

* Roller coasters * Conveyor systems *

Beverage A drink or beverage is a liquid intended for human consumption. In addition to their basic function of satisfying thirst, drinks play important roles in human culture. Common types of drinks include plain drinking water, milk, juice, smoo ...

and

food can A steel can, tin can, tin (especially in British English, Australian English, Canadian English and South African English), steel packaging, or can is a Packaging and labeling, container for the distribution or storage of goods, made of t ...

making lines *

Mobile device A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physical ...

s **

Touch screen A touchscreen or touch screen is the assembly of both an input ('touch panel') and output ('display') device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is ofte ...

s that come in close proximity to the face ** Attenuating radio power in close proximity to the body, in order to reduce radiation exposure * Automatic faucets

References

{{Authority control Position sensors

Use with smartphones and tablet computers

Types of sensors

Applications

See also

References