Proximity sensor
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A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. 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 might be suitable for a plastic target; an inductive proximity sensor always requires a metal target.[citation needed]
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 turbines, compressors, and motors that use sleeve-type bearings.
A proximity sensor adjusted to a very short range is often used as a touch switch.
Use with smartphones and tablet computers
Proximity sensors are commonly used on mobile devices.[1] When the target is within nominal range, the device lock screen user interface will appear, thus emerging from what is known as sleep mode. Once the device has awoken from sleep mode, 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 sleep mode. For example, during a telephone call, proximity sensors play a role in detecting (and skipping) accidental touchscreen taps when mobiles are held to the ear.[2]
Proximity sensors can be used to recognise air gestures and hover-manipulations. An array of proximity sensing elements can replace vision-camera or depth camera based solutions for hand gesture detection.
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The pulsing proximity sensor of a BlackBerry Leap -
Video of the pulsing proximity sensor of a BlackBerry Leap
Types of sensors
- Capacitive
- Capacitive displacement sensor
- Doppler effect (sensor based on doppler effect)
- Inductive
- Magnetic, including magnetic proximity fuse
- Optical
- Photoelectric
- Photocell (reflective)
- Laser rangefinder
- Passive (such as charge-coupled devices)
- Passive thermal infrared
- Radar
- Reflection of ionizing radiation
- Sonar (typically active or passive)
- Ultrasonic sensor
- Fiber optics sensor
- Hall effect sensor
Type of Proximity Sensors
In the Industrial Automation process mainly there are 2 types of Proximity Sensors available 1. Inductive Proximity Sensors 2. Capacitive Proximity Sensors Inductive Proximity Sensors: Inductive proximity sensors are non-contact sensing devices used to detect metallic objects, typically without physical contact. They operate based on the principle of electromagnetic induction, where a magnetic field is created around the sensor's sensing face. When a metallic object is brought into close proximity to the sensing face, it influences the magnetic field and creates a change in the sensor's output.
Inductive proximity sensors are widely used in industrial applications for detecting the presence or absence of metal components, such as shafts, gears, or metal sheets. They are known for their robustness, immunity to environmental effects such as dust, moisture, and vibration, and high reliability.
Inductive proximity sensors come in different shapes, sizes, and configurations, including cylindrical, rectangular, and tubular, with different sensing ranges, output types (analog or digital), and electrical connections. They can also be designed to operate in hazardous or harsh environments, such as high-temperature or explosive atmospheres.
Capacitive Proximity Sensors: Capacitive proximity sensors are non-contact sensing devices used to detect the presence of a nearby object, typically without physical contact. They operate based on the principle of capacitance, where the electrical capacitance between the sensor and the target object changes as the distance between them changes.
Capacitive proximity sensors are used to detect the presence of non-metallic objects, such as liquids, plastics, or dielectric materials. They can be used in applications where the sensing target has a different dielectric constant than its surroundings, such as detecting the level of a liquid in a tank.
Capacitive proximity sensors are typically more sensitive than inductive proximity sensors and can detect objects at a closer range. They can also be designed to detect objects through non-metallic containers or containers with non-uniform walls. However, they can be influenced by environmental factors such as temperature changes, humidity, and the presence of conductive materials in the vicinity.
Like inductive proximity sensors, capacitive proximity sensors come in different shapes, sizes, and configurations, including cylindrical, rectangular, and tubular, with different sensing ranges, output types (analog or digital), and electrical connections. They can also be designed to operate in hazardous or harsh environments, such as high-temperature or explosive atmospheres.
Inductive Proximity Sensors Vs Capacitive Proximity Sensors Inductive proximity sensors and capacitive proximity sensors are two types of non-contact sensing devices used to detect the presence of nearby objects. While they both have the same basic function, they operate on different principles and have different strengths and weaknesses. Here are some of the key differences between inductive proximity sensors and capacitive proximity sensors:
Operating principle: Inductive proximity sensors operate based on the principle of electromagnetic induction, while capacitive proximity sensors operate based on the principle of capacitance.
Sensing target: Inductive proximity sensors are used to detect metallic objects, while capacitive proximity sensors are used to detect non-metallic objects, such as liquids or dielectric materials.
Sensitivity: Capacitive proximity sensors are typically more sensitive than inductive proximity sensors and can detect objects at a closer range. However, they can be influenced by environmental factors such as temperature changes and humidity.
Immunity to environmental effects: Inductive proximity sensors are more immune to environmental effects, such as dust and moisture, compared to capacitive proximity sensors.
Electrical connections: Both inductive and capacitive proximity sensors come in different shapes, sizes, and configurations, with different sensing ranges, output types (analog or digital), and electrical connections.
Cost: Inductive proximity sensors are generally less expensive than capacitive proximity sensors.
In simple, the choice between inductive and capacitive proximity sensors depends on the specific application requirements and the type of target to be detected. Both types of proximity sensors have their advantages and limitations, and the right choice will depend on factors such as the sensing range, the type of target, environmental conditions, and the required output signal. For more in-depth details you can check the proximity sensor guide.
Applications
- Parking sensors, 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[citation needed]
- Top dead centre (TDC)/camshaft sensor in reciprocating engines.
- Sheet break sensing in paper machine.
- Anti-aircraft warfare
- Roller coasters
- Conveyor systems
- Beverage and food can making lines
- Mobile devices
- Touch screens that come in close proximity to the face[2]
- Attenuating radio power in close proximity to the body, in order to reduce radiation exposure[3]
- Automatic faucets
See also
References
- ^ O'Brien, Daniel J. (2021-03-22). "A guide for incorporating e-teaching of physics in a post-COVID world". American Journal of Physics. 89 (4): 403–412. doi:10.1119/10.0002437. ISSN 0002-9505. S2CID 221139614.
- ^ a b "Proximity sensor on Android smartphones". TheCodeArtist.
- ^ Phillips, Jon. "Can a $100 iPad Case Improve 3G Data Power? Lab Test!". Wired.
