| A sensor is a type of transducer. | | | | retroreflector. The return time of the |
| Direct-indicating sensors, for example, | | | | pulse is proportional to the distance |
| a mercury thermometer, are | | | | and is related to atmospheric density in |
| human-readable. Other sensors must be | | | | a predictable way. |
| paired with an indicator or display, for | | | | light sensors, or photodetectors, |
| instance a thermocouple. Most sensors | | | | including semiconductor devices such as |
| are electrical or electronic, although | | | | photocells, photodiodes, |
| other types exist. | | | | phototransistors, CCDs, and Image |
| Sensors are used in everyday life. | | | | sensors; vacuum tube devices like |
| Applications include automobiles, | | | | photo-electric tubes, photomultiplier |
| machines, aerospace, medicine, industry | | | | tubes; and mechanical instruments such |
| and robotics. | | | | as the Nichols radiometer. |
| Technological progress allows more and | | | | infra-red sensor, especially used as |
| more sensors to be manufactured on the | | | | occupancy sensor for lighting and |
| microscopic scale as microsensors using | | | | environmental controls. |
| MEMS technology. In most cases a | | | | proximity sensor- A type of distance |
| microsensor reaches a significantly | | | | sensor but less sophisticated. Only |
| higher speed and sensitivity compared | | | | detects a specific proximity. May be |
| with macroscopic approaches. Types | | | | optical - combination of a photocell and |
| Since a significant change involves an | | | | LED or laser. Applications in cell |
| exchange of energy, sensors can be | | | | phones, paper detector in photocopiers, |
| classified according to the type of | | | | auto power standby/shutdown mode in |
| energy transfer that they detect. | | | | notebooks and other devices. May employ |
| Thermal | | | | a magnet and a Hall effect device. |
| temperature sensors: thermometers, | | | | scanning laser- A narrow beam of laser |
| thermocouples, temperature sensitive | | | | light is scanned over the scene by a |
| resistors (thermistors and resistance | | | | mirror. A photocell sensor located at an |
| temperature detectors), bi-metal | | | | offset responds when the beam is |
| thermometers and thermostats | | | | reflected from an object to the sensor, |
| heat sensors: bolometer, calorimeter | | | | whence the distance is calculated by |
| Electromagnetic | | | | triangulation. |
| electrical resistance sensors: ohmmeter, | | | | focus. A large aperture lens may be |
| multimeter | | | | focused by a servo system. The distance |
| electrical current sensors: | | | | to an in-focus scene element may be |
| galvanometer, ammeter | | | | determined by the lens setting. |
| electrical voltage sensors: leaf | | | | binocular. Two images gathered on a |
| electroscope, voltmeter | | | | known baseline are brought into |
| electrical power sensors: watt-hour | | | | coincidence by a system of mirrors and |
| meters | | | | prisms. The adjustment is used to |
| magnetism sensors: magnetic compass, | | | | determine distance. Used in some cameras |
| fluxgate compass, magnetometer, Hall | | | | (called range-finder cameras) and on a |
| effect device | | | | larger scale in early battleship |
| metal detectors | | | | range-finder |
| RADAR | | | | interferometry. Interference fringes |
| Mechanical | | | | between transmitted and reflected |
| pressure sensors: altimeter, barometer, | | | | lightwaves produced by a coherent source |
| barograph, pressure gauge, air speed | | | | such as a laser are counted and the |
| indicator, rate of climb indicator, | | | | distance is calculated. Capable of |
| variometer | | | | extremely high precision. |
| gas and liquid flow sensors: flow | | | | Scintillometers measure atmospheric |
| sensor, anemometer, flow meter, gas | | | | optical disturbances. |
| meter, water meter, mass flow sensor | | | | Fiber Optic sensors |
| mechanical sensors: acceleration sensor, | | | | Ionising radiation |
| position sensor, selsyn, switch, strain | | | | radiation sensors: Geiger counter, |
| gauge | | | | dosimeter, Scintillation counter, |
| Chemical | | | | Neutron detection |
| Chemical sensors detect the presence of | | | | subatomic particle sensors: Particle |
| specific chemicals or classes of | | | | detector, scintillator, Wire chamber, |
| chemicals. Examples include oxygen | | | | cloud chamber, bubble chamber. See |
| sensors, also known as lambda sensors, | | | | Category:Particle detectors |
| ion-selective electrodes, pH glass | | | | Acoustic |
| electrodes, and redox electrodes. | | | | acoustic : uses ultrasound |
| A carbon monoxide detector is a chemical | | | | time-of-flight echo return. Used in mid |
| sensor often used in the home. These | | | | 20th century polaroid cameras and |
| detectors continually sample air and | | | | applied also to robotics. Even older |
| will sound an alarm if the amount of | | | | systems like Fathometers (and fish |
| invisible, odorless, and potentially | | | | finders) and other 'Tactical Active' |
| deadly carbon monoxide levels in our | | | | Sonar (Sound Navigation And Ranging) |
| home and/or workplace rises above 400 | | | | systems in naval applications which |
| PPM. | | | | mostly use audible sound frequencies. |
| In manufacturing, chemical sensors are | | | | sound sensors : microphones, |
| used to manage process controls, quality | | | | hydrophones, seismometers. |
| assurance, and safety. | | | | Other types |
| The engine management systems of | | | | motion sensors: radar gun, speedometer, |
| automobiles take information from | | | | tachometer, odometer, occupancy sensor, |
| sensors and adjust engine parameters to | | | | turn coordinator |
| achieve the best mix of fuel economy, | | | | orientation sensors: gyroscope, |
| performance and emissions. Oxygen | | | | artificial horizon, ring laser gyroscope |
| sensors have been used in automobiles | | | | distance sensor (noncontacting) Several |
| since the late 70’s. Many areas | | | | technologies can be applied to sense |
| require automobiles to pass an emissions | | | | distance: magnetostriction |
| test annually. The test equipment also | | | | Non Initialized systems |
| uses chemical sensors to check the | | | | Gray code strip or wheel- a number of |
| exhaust emissions. | | | | photodetectors can sense a pattern, |
| Chemical sensors have been developed to | | | | creating a binary number. The gray code |
| detect threats from explosives and | | | | is a mutated pattern that ensures that |
| biological weapons. Monitoring for these | | | | only one bit of information changes with |
| threats includes border crossings, major | | | | each measured step, thus avoiding |
| transportation systems, and large public | | | | ambiguities. |
| spaces.[1] For example, airport security | | | | Initialized systems |
| utilizes chemical sensors used to sniff | | | | These require starting from a known |
| out explosives and even drugs.[2] | | | | distance and accumulate incremental |
| Chemical sensors are also being | | | | changes in measurements. |
| developed to sniff out illnesses in | | | | Quadrature wheel- An disk-shaped optical |
| people.[3] | | | | mask is driven by a gear train. Two |
| In supramolecular analytical chemistry | | | | photocells detecting light passing |
| novel molecular sensors are developed | | | | through the mask can determine a partial |
| for a wide range of such applications. | | | | revolution of the mask and the direction |
| Optical radiation | | | | of that rotation. |
| light time-of-flight. Used in modern | | | | whisker sensor- A type of touch sensor |
| surveying equipment, a short pulse of | | | | and proximity sensor. |
| light is emitted and returned by a | | | | |