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{{Copy edit|date=February 2024}}
{{Use American English|date = March 2019}}
{{Short description|Devices that measure magnetic field strength using the Hall effect}}

[[File:Hall sensor tach.gif|220x220px|thumb|Figure 1: a wheel containing two [[magnets]] passing by a Hall effect sensor. The voltage from the sensor peaks twice for each revolution. This arrangement is used to measure and regulate the speed of rotating objects, including [[Disk storage|disk drives]].]]A '''Hall effect sensor''' (or a '''Hall sensor''' or '''Hall probe''') is any [[sensor]] incorporating one or more Hall elements, each of which produce a [[voltage]] proportional to one axial component of the [[Magnetic field#The B-field|magnetic field vector {{math|'''B'''}}]] using the [[Hall effect]] (named for physicist [[Edwin Hall]]).

Hall sensors are used for [[proximity sensing]], [[positioning (navigation)|positioning]], [[Speed limit enforcement|speed detection]], and [[current sensing]] applications<ref name="ramsden">{{cite book |last=Ramsden |first=Edward |url=https://books.google.com/books?id=R8VAjMitH1QC |title=Hall-effect sensors: theory and applications |publisher=[[Elsevier]] |year=2006 |isbn=978-0-7506-7934-3 |edition=2, illustrated}}</ref> and are common in industrial and consumer applications. Hundreds of millions of Hall sensor [[integrated circuits]] (ICs) are sold each year<ref>{{Cite web |title=How the Hall Effect Still Reverberates - IEEE Spectrum |url=https://spectrum.ieee.org/hall-effect-sensor |access-date=2023-12-28 |website=spectrum.ieee.org |language=en}}</ref> by ~50 manufacturers, with the global market around a billion [[United States dollar|dollars]].<ref>{{Cite web |last= |first= |date=2021-07-01 |title=Global Industry Analysts: Global Hall-Effect Current Sensors Market to Reach $1.3 Billion by 2026 |url=https://www.prnewswire.com/news-releases/global-hall-effect-current-sensors-market-to-reach-1-3-billion-by-2026--301324188.html |access-date=2023-12-28 |website=www.prnewswire.com |language=en}}</ref>

== Principles ==
[[File:Common Hall Sensor Symbol.png|thumb|Hall element circuit symbol|97x97px]]{{Main article|Hall effect#Theory}}
In a Hall sensor, a fixed [[DC current|DC]] bias current<ref name=":0">{{Cite web |title=Hall Effect Sensor {{!}} Applications Guide |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/hall-effect-ic-applications-guide |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> is applied along one axis across a thin strip of metal called the Hall element [[transducer]]. Sensing electrodes on opposite sides of the Hall element along ''another'' axis measure the difference in [[electric potential]] ([[voltage]]) across the axis of the electrodes. The current's charge carriers are deflected by the [[Lorentz force]] in the presence of a magnetic field perpendicular to their flow. The sensing electrodes measure the potential difference (the Hall voltage) proportional to the axial component of the magnetic field that is perpendicular to ''both'' the current's axis and the sensing electrodes' axis.<ref>{{cite book |title= Hall effect devices |first= R. S.|last=Popović |edition= 2, illustrated |publisher= [[CRC Press]] |year= 2004 |isbn= 978-0-7503-0855-7 |url= https://books.google.com/books?id=_H5n-5sO5BAC&q=hall+effect+sensor&pg=PA1 }}</ref>

Hall effect sensors respond to static and changing magnetic fields. [[inductive sensor|Inductive sensors]] instead only respond to changes in fields.

=== Amplification ===
Hall effect devices produce a very low signal level and thus require amplification. While suitable for laboratory instruments, the [[vacuum tube]] [[Amplifier|amplifiers]] available in the first half of the 20th century were too expensive, power-consuming, and unreliable for everyday applications. It was only with the development of the low cost [[integrated circuit]] that the Hall effect sensor became suitable for mass application. Devices sold as Hall sensors nowadays contain both the sensor as described above and a high gain [[integrated circuit]] (IC) amplifier in a single package. These Hall sensor ICs may add a stable [[voltage regulator]] in addition to the [[amplifier]] to allow operation over a wide range of [[Voltage source|supply voltage]] and boost the Hall voltage for a convenient analog signal output proportional to the magnetic field component.<ref name=":0" /> In some cases, the linear circuit may cancel the offset voltage of Hall sensors. Moreover, AC modulation of the driving current may also reduce the influence of this offset voltage.

Hall sensors are called ''linear'' if their output is proportional to the incident magnetic field strength. This output signal can be an [[Analog signal|analog]] voltage, a [[pulse-width modulation]] (PWM) signal, or be [[Digital communication|communicated digitally]] over a modern [[Bus (computing)#Examples of internal computer buses|bus protocol]].<ref>{{Cite web |title=Linear Hall Sensors (product category) |url=https://product.tdk.com/en/products/sensor/linear/linear-hall/index.html |url-status=live |archive-url=https://web.archive.org/web/20230205002539/https://product.tdk.com/en/products/sensor/linear/linear-hall/index.html |archive-date=2023-02-05 |access-date=2024-01-02 |website=[[TDK]]}}</ref> Hall sensors may also be ''ratiometric'' if their sensitivity is also proportional to their supply voltage. With no magnetic field applied, their ''quiescent output voltage'' is typically{{Sfrac|supply voltage|2}}.<ref>{{Cite web |last1=Gilbert |first1=Joe |last2=Dewey |first2=Ray |date=2022-05-05 |title=AN27702: Linear Hall-Effect Sensor ICs |url=https://www.allegromicro.com/-/media/files/application-notes/an27702-linear-hall-effect-sensor-ics.pdf |url-status=live |archive-url=https://web.archive.org/web/20231104000208/https://www.allegromicro.com/-/media/files/application-notes/an27702-linear-hall-effect-sensor-ics.pdf |archive-date=2023-11-04 |access-date=2024-01-02 |website=[[Allegro MicroSystems]]}}</ref> They may have [[Rail-to-rail opamp|rail-to-rail]] output (e.g. A1302).<ref>https://www.jameco.com/Jameco/Products/ProdDS/2135881.pdf {{bare URL PDF|date=March 2024}}</ref>

=== Hall switch ===
While the Hall element is an [[analog device]], ''Hall switch'' ICs often additionally incorporate [[Threshold detector|threshold detection]] circuitry to form an [[electronic switch]] which has two states (on and off) that output a binary [[digital signal]].

Their outputs may be [[open collector]] [[NPN transistor|NPN transistors]] (or open drain n-type [[MOSFETs]]) for compatibility with ICs that use different supply voltages.<ref name=":0" /> Rather than a voltage being produced at the Hall sensor signal output wire, an output transistor is turned on, providing a circuit to ground through the signal output wire.

==== Hysteresis ====
[[Schmitt trigger]] filtering may be applied (or integrated in the IC) to provide a clean digital output that is [[Robustness|robust]] against sensor noise. The [[hysteresis]] thresholds for switching (specified as B{{Sub|OP}} and B{{Sub|RP}}) categorize digital Hall ICs as either unipolar switches,<ref>{{Cite web |title=Unipolar Hall-Effect Sensor IC Basics |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/unipolar-hall-effect-sensor-ic-basics |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> omnipolar switches,<ref>{{Cite web |title=Omnipolar Switch Hall-Effect IC Basics {{!}} Allegro MicroSystems |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/omnipolar-switch-hall-effect-ic-basics |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> or bipolar switches,<ref>{{Cite web |title=Bipolar Switch Hall-Effect ICs |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/bipolar-switch-hall-effect-ics |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> which may sometimes be called latches.<ref>{{Cite web |title=AN296067: Hall Effect Switch {{!}} Latching Switch Basics |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/latching-switch-hall-effect-ic-basics |url-status=live |archive-url=https://web.archive.org/web/20230927181352/https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/latching-switch-hall-effect-ic-basics |archive-date=2023-09-27 |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> Unipolar (e.g. A3144)<ref>https://www.elecrow.com/download/A3141-2-3-4-Datasheet.pdf {{bare URL PDF|date=March 2024}}</ref> refers to having switching thresholds in only one polarity of the magnetic field. Omnipolar switches have two sets of switching thresholds, for both positive and negative polarities, and so operate alternatively with a strong positive or a strong negative magnetic field.

Bipolar switches have a positive B{{Sub|OP}} and negative B{{Sub|RP}} (and thus require both positive and negative magnetic fields to operate). The difference between B{{Sub|OP}} and B{{Sub|RP}} tends to be greater for bipolar switches described as latches, which remain in one state much longer (i.e. they latch onto their last value) and require a more significant field strength to change states than bipolar switches require. The naming distinction between "bipolar" and "latch" may be a little arbitrary, for instance the datasheet for the [[Honeywell]] SS41F describes it as "bipolar" while another manufacturer describes their SS41F<ref>https://radiolux.com.ua/files/pdf/SS41F.pdf {{bare URL PDF|date=March 2024}}</ref> with comparable specifications as a "latch". 

== Characteristics ==

=== Directionality ===
Hall elements measure only the sensing axis component of the magnetic field vector. Because that axial component may be positive or negative, some Hall sensors are able to sense that binary direction of the axial component in addition to its magnitude. An additional perpendicularly-oriented Hall element (e.g. in {{Slink|Hall effect sensor|Dual Hall sensor ICs|nopage=y}}) must be incorporated to determine a 2-D direction, and another perpendicularly-oriented Hall element must be added to detect the full 3-D components of the magnetic field vector.

=== Solid state ===
Because Hall sensor ICs are [[Solid-state electronics|solid state devices]], they are not prone to mechanical wear. Thus, they can operate at much higher speeds than mechanical sensors and their lifespan is not limited by mechanical failure (unlike [[potentiometers]], [[electromechanical]] [[Reed switch|reed switches]],<ref>{{cite web |last1=Staff Writer |title=How to Decide Between a Reed Switch or a Hall Switch |url=https://www.thomasnet.com/insights/how-to-decide-between-a-reed-switch-or-a-hall-switch/ |website=I.I. Thomas |access-date=20 April 2021}}</ref> [[relays]], or other mechanical [[switches]] and sensors). However, Hall sensors can be prone to thermal drift due to changes in environmental conditions, and to time drift over the lifetime of the sensor.<ref>{{cite web |last1=Hertz |first1=Jake |title=Engineers Deal With Drift in Many Ways. What About a "Zero Drift" Hall-Effect Current Sensor? |url=https://www.allaboutcircuits.com/news/engineers-deal-with-drift-many-ways-zero-drift-hall-effect-current-sensor/ |website=All About Circuits |access-date=20 April 2021}}</ref>

Hall effect devices (when appropriately packaged) are immune to dust, dirt, mud, and water. These characteristics make Hall effect devices better for position sensing than alternative means such as optical and electromechanical sensing.

=== Bandwidth ===
Bandwidth of practical Hall sensors are limited to the hundreds of [[kilohertz]], with commercial [[silicon]] ones commonly limited to 10–100 kHz. {{As of|2016}}, the fastest Hall sensor available in the market has a bandwidth of 1 MHz, but uses non-standard semiconductors.<ref>{{Cite web |last=Crescentini |first=M. |date=2016-09-07 |title=Experimental Characterization of Bandwidth Limits in Hall Sensors |url=https://www.imeko.org/publications/tc4-2016/IMEKO-TC4-2016-01.pdf |url-status=live |archive-url=https://web.archive.org/web/20231230033926/https://www.imeko.org/publications/tc4-2016/IMEKO-TC4-2016-01.pdf |archive-date=2023-12-30 |access-date=2023-12-30}}</ref>

=== Susceptibility to external fields ===
Magnetic flux from the surroundings (such as other wires) may diminish or enhance the field the Hall probe intends to detect, rendering the results inaccurate. Hall sensors can detect stray magnetic fields easily, including that of Earth, so they work well as electronic compasses: but this also means that such stray fields can hinder accurate measurements of small magnetic fields. To solve this problem, Hall sensors are often integrated with magnetic shielding of some kind.

Mechanical positions within an electromagnetic system can instead be measured without the Hall effect using [[optical]] position encoders (e.g., absolute and [[Incremental encoder|incremental encoders]]) and [[Faraday's law of induction|induced voltage]] by moving the amount of metal core inserted into a [[transformer]]. When Hall is compared to photo-sensitive methods, it is harder to get absolute position with Hall.

==== Differential Hall sensors ====
While a single Hall element is susceptible to external magnetic fields, a differential configuration of two Hall elements can cancel stray fields out from measurements,<ref>{{Cite web |last=Palvik |first=Scott |date=2019-08-27 |title=Differential Hall-Effect Sensors: Safer and More Reliable for Two-Wheelers of the Future |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/an296173-differential-hall-effect-sensors |url-status=live |archive-url=https://web.archive.org/web/20231230032307/https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/an296173-differential-hall-effect-sensorsor-ic-publications/an296173-differential-hall-effect-sensors |archive-date=2023-12-30 |access-date=2023-12-30 |website=www.allegromicro.com}}</ref> analogous to how common mode voltage signals are cancelled using [[differential signalling]].

== Materials ==

The following materials are especially suitable for Hall effect sensors:<ref>{{cite book |first1=Oleg |last1=Petruk |first2=Roman |last2=Szewczyk |first3=Tymoteusz |last3=Ciuk |first4=Włodzimierz |last4=Strupiński |first5=Jacek |last5=Salach |first6=Michał |last6=Nowicki |first7=Iwona |last7=Pasternak |first8=Wojciech |last8=Winiarski |first9=Krzysztof |last9=Trzcinka |date=2014 |title=Sensitivity and Offset Voltage Testing in the Hall-Effect Sensors Made of Graphene |publisher=Springer |volume=267 |pages=631 |doi=10.1007/978-3-319-05353-0_60 |display-authors=3 |series=Advances in Intelligent Systems and Computing |isbn=978-3-319-05352-3 }}</ref>

* [[Gallium arsenide]] (GaAs)
* [[Indium arsenide]] (InAs)
* [[Indium phosphide]] (InP)
* [[Indium antimonide]] (InSb)
* [[Graphene]]

== Applications ==
[[File:Cylinders with Hall sensors.png|thumb|Figure 2: the magnetic piston (1) in this [[pneumatic cylinder]] will cause the Hall effect sensors (2 and 3) mounted on its outer wall to activate when it is fully retracted or extended.]]
[[File:Clutch with Hall Effect sensor.jpg|thumb|Engine fan with Hall effect sensor]] 

Hall effect sensors may be used in various sensors such as rotating speed sensors (bicycle wheels, gear-teeth, automotive speedometers, electronic ignition systems), fluid [[Flow sensor|flow sensors]], [[Current sensor|current sensors]], and [[Pressure sensor|pressure sensors]]. Hall sensors are commonly used to time the speed of wheels and shafts (e.g. Figure 1), such as for [[internal combustion engine]] [[ignition timing]], [[tachometer]]s and [[anti-lock braking system]]s.

Common applications are often found where a [[Robustness|robust]] and contactless alternative to a mechanical switch or potentiometer is required. These include: electric [[airsoft]] guns, triggers of electropneumatic [[Paintball marker|paintball guns]], [[go-kart]] speed controls, [[smartphones]], and some global positioning systems.

=== Position sensing ===
One of the most common industrial applications of Hall sensors used as binary switches is in position sensing (e.g. Figure 2).

Hall effect sensors are used to detect whether a smartphone's cover (that includes a small magnet) is closed.<ref>{{cite web |title=ZenFone 5 (A500CG) |url=https://www.asus.com/Phone/ZenFone_5_A500CG/specifications/ |access-date=2 September 2017 |website=asus.com}}</ref>

Some [[computer printer]]s use Hall sensors to detect missing paper and open covers and some 3D printers use them to measure filament thickness.

Hall sensors are used in some automotive fuel-level indicators by detecting the position of a floating element in the fuel tank.<ref>{{cite web |date=12 February 2009 |title=Liquid Level Sensing: Measuring Liquid Levels Using Hall Effect Sensors |url=https://www.infineon.com/dgdl/AppNote_Liquid_Level_Sensing_Rev.1.0.pdf?folderId=db3a30431ce5fb52011d4cae1f582dad&fileId=db3a30432313ff5e0123a385f3b2262d |access-date=2 September 2017 |website=infineon.com}}</ref>

Hall sensors affixed to mechanical gauges that have magnetized indicator needles can translate the physical position or orientation of the mechanical indicator needle into an electrical signal that can be used by electronic indicators, controls or communications devices.<ref name="esi_tank_sensors">[http://www.leveldevilsensors.com/main/electronic-sensors-inc-esi-level-devil-american-made-tank-monitors-and-tank-monitoring-systems/tabk-sensor/ Tank Sensors & Probes], Electronic Sensors, Inc., retrieved August 8, 2018</ref>

=== Magnetometers ===
[[Magnetometers#Hall effect magnetometer|Hall effect magnetometers]] (also called teslameters or gaussmeters) use a ''Hall probe''<ref>{{Cite web |title=Hall probes |url=https://www.lakeshore.com/products/categories/magnetic-products/hall-probes |access-date=2023-12-29 |website=Lake Shore Cryotronics |language=en}}</ref> with a Hall element to measure magnetic fields or inspect materials (such as tubing or pipelines) using the principles of [[magnetic flux leakage]]. A Hall probe is a device that uses a calibrated Hall effect sensor to directly measure the strength of a magnetic field. Since magnetic fields have a direction as well as a magnitude, the results from a Hall probe are dependent on the orientation, as well as the position, of the probe.

=== Ammeters ===
Hall sensors may be utilized for contactless measurements of [[direct current]] in [[current transformer]]s. In such a case the Hall sensor is mounted in a gap in the magnetic core around the current conductor.<ref>{{cite book |last1=Petruk |first1=O. |title=Digitally Controlled Current Transformer with Hall Sensor |last2=Szewczyk |first2=R. |last3=Salach |first3=J. |last4=Nowicki |first4=M. |date=2014 |publisher=Springer |isbn=978-3-319-05352-3 |series=Advances in Intelligent Systems and Computing |volume=267 |pages=641 |doi=10.1007/978-3-319-05353-0_61}}</ref> As a result, the DC [[magnetic flux]] can be measured, and the DC current in the conductor can be calculated.

[[File:HallEffCurrentSense.jpg|right|thumb|250x250px|Hall effect current sensor with internal integrated circuit amplifier. 8 mm opening. Zero current output voltage is midway between the supply voltages that maintain a 4 to 8 volt differential. Non-zero current response is proportional to the voltage supplied and is linear to 60 amperes for this particular (25&nbsp;A) device.]]

When electrons flow through a conductor, a magnetic field is produced. Thus, it is possible to create a non-contacting [[current sensor]] or [[ammeters]]. The device has three terminals. A sensor voltage is applied across two terminals and the third provides a voltage proportional to the current being sensed. This has several advantages; no additional resistance (a [[Shunt (electrical)|''shunt'']], required for the most common current sensing method) need to be inserted in the primary circuit. Also, the voltage present on the line to be sensed is not transmitted to the sensor, which enhances the safety of measuring equipment.[[File:RAZC-GENARRv1.jpg|left|thumb|Diagram of Hall effect current [[transducer]] integrated into ferrite ring]]
[[File:Ampere-Turnsv1.jpg|thumb|Multiple 'turns' and corresponding transfer function]]

==== Improving signal-to-noise ====
Integrating a Hall sensor into a ferrite ring (as shown) concentrates the flux density of the current's magnetic field along the ferrite ring and through the sensor (because flux flows through ferrite much better than through air),<ref name=":02">{{Cite web |title=Hall Effect Sensor {{!}} Applications Guide |url=https://www.allegromicro.com/en/insights-and-innovations/technical-documents/hall-effect-sensor-ic-publications/hall-effect-ic-applications-guide |access-date=2023-12-28 |website=www.allegromicro.com}}</ref> which greatly reduces the relative influence of stray fields by a factor of 100 or better. This configuration also provides an improvement in [[signal-to-noise ratio]] and drift effects of over 20 times that of a bare Hall device.

The range of a given feedthrough sensor may also be extended upward and downward by appropriate wiring. To extend the range to lower currents, multiple turns of the current-carrying wire may be made through the opening, each turn adding to the sensor output the same quantity; when the sensor is installed onto a printed circuit board, the turns can be carried out by a staple on the board. To extend the range to higher currents, a current divider may be used. The divider splits the current across two wires of differing widths and the thinner wire, carrying a smaller proportion of the total current, passes through the sensor.

==== Current clamp ====
{{Main article|Current clamp}}
A variation on the ring sensor uses a [[Current clamp#Hall effect|split sensor]] which is clamped onto the line enabling the device to be used in temporary test equipment. If used in a permanent installation, a split sensor allows the electric current to be tested without dismantling the existing circuit.

The output is proportional to both the applied magnetic field and the applied sensor voltage. If the magnetic field is applied by a solenoid, the sensor output is proportional to the product of the current through the solenoid and the sensor voltage. As most applications requiring computation are now performed by small [[Computer|digital computers]], the remaining useful application is in power sensing, which combines current sensing with voltage sensing in a single Hall effect device.

By sensing the current provided to a load and using the device's applied voltage as a sensor voltage it is possible to determine the power dissipated by a device to form a [[wattmeter]].

=== Motion sensing ===
Hall effect devices used in motion sensing and motion limit switches can offer enhanced reliability in extreme environments. As there are no moving parts involved within the sensor or magnet, typical life expectancy is improved compared to traditional electromechanical switches. Additionally, the sensor and magnet may be encapsulated in an appropriate protective material.

==== Ignition timing ====
Commonly used in distributors for ignition timing (and in some types of crank- and camshaft-position sensors for injection pulse timing, speed sensing, etc.) the Hall Effect sensor is used as a direct replacement for the [[Contact breaker|mechanical breaker points]] used in earlier automotive applications. Its use as an ignition timing device in various distributor types is as follows: a stationary permanent magnet and semiconductor Hall Effect chip are mounted next to each other separated by an air gap, forming the Hall Effect sensor.

A metal rotor consisting of windows or tabs is mounted to a shaft and arranged so that during shaft rotation, the windows or tabs pass through the air gap between the permanent magnet and semiconductor Hall chip. This effectively shields and exposes the Hall chip to the permanent magnet's field respective to whether a tab or window is passing through the Hall sensor. For ignition timing purposes, the metal rotor will have a number of equal-sized windows or tabs matching the number of engine cylinders (#1 cylinder tab will always be unique for discernment by the Engine Control Unit).

This produces a uniform output similar to a [[square wave]] since the shielding and exposure time is equal. This signal is used by the engine computer or ECU to control ignition timing.

==== Anti-lock braking ====
The sensing of wheel rotation is especially useful in [[Anti-lock braking system|anti-lock braking systems]]. The principles of such systems have been extended and refined to offer more than anti-skid functions, now providing extended vehicle [[Automobile handling|handling]] enhancements.

==== Brushless motors ====
Some types of [[Brushless DC electric motor|brushless DC electric motors]] use Hall effect sensors to detect the position of the rotor and feed that information to the motor controller. This allows for more precise motor control. Hall sensors in 3 or 4 pin [[Brushless DC electric motor|brushless DC motor]]s sense the position of the rotor and to switch the [[Transistor|transistors]] in the right sequence.<ref>{{Cite journal |last=Burke |first=Mary |date=February 2004 |title=Why and How to Control Fan Speed for Cooling Electronic Equipment |url=https://www.analog.com/en/analog-dialogue/articles/how-to-control-fan-speed.html |journal=Analog Dialogue |volume=38}}</ref>

=== Hall-effect thruster ===
{{Main article|Hall-effect thruster}}
A [[Hall-effect thruster]] (HET) is a device that is used to propel some [[spacecraft]], after it gets into [[orbit]] or farther out into space. In the HET, [[Atom|atoms]] are [[Ionization|ionized]] and accelerated by an [[electric field]]. A radial magnetic field established by magnets on the thruster is used to trap [[Electron|electrons]] which then orbit and create an [[electric field]] due to the Hall effect. A large potential is established between the end of the thruster where neutral propellant is fed, and the part where electrons are produced; so, electrons trapped in the magnetic field cannot drop to the lower potential.  They are thus extremely energetic, which means that they can ionize neutral atoms. Neutral propellant is pumped into the chamber and is ionized by the trapped electrons.  Positive ions and electrons are then ejected from the thruster as a quasineutral [[Plasma (physics)|plasma]], creating thrust.  The thrust produced is extremely small, with a very low mass flow rate and a very high effective exhaust velocity/specific impulse. This is achieved at the cost of very high electrical power requirements, on the order of 4 kW for a few hundred millinewtons of thrust.

=== Integrated digital electronics ===
Hall sensors ICs often integrate digital electronics.<ref>{{cite web |title=Hall Effect Sensor Voltage Regulation and Power Management |url=http://phareselectronics.com/products/hall-effect-sensors/voltage-regulation-and-power-management/ |website=phareselectronics.com |access-date=26 May 2015 |archive-date=29 May 2015 |archive-url=https://web.archive.org/web/20150529055232/http://phareselectronics.com/products/hall-effect-sensors/voltage-regulation-and-power-management/ |url-status=dead }}</ref> This enables advanced corrections to the sensor characteristics (e.g. temperature-coefficient corrections), [[digital communication]] to microprocessor systems, and may provide interfaces for input diagnostics, fault protection for transient conditions, and short/open-circuit detection.

Some Hall sensor ICs integrated a [[digital signal processing|DSP]], which can allow more processing techniques directly within the sensor package.<ref name="ramsden" />{{rp|167}}

Some Hall sensor ICs integrate an [[analog-to-digital converter]] and [[I2C|I<sup>2</sup>C]] (Inter-integrated circuit communication protocol) IC for direct connection to a [[microcontroller]]'s I/O port.<ref>https://www.mouser.com/c/sensors/magnetic-sensors/?q=I2C or any other part distributor search for "I2C" and "Hall sensor"</ref>

The [[ESP32]] [[microcontroller]] even has an integrated a Hall sensor which hypothetically could be read by the microcontroller's internal [[analog-to-digital converter]], though it does not work.<ref>[https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf ESP32Technical Reference Manual] V4.9 2023 revision history removed mention of the sensor. [https://www.espressif.com/sites/default/files/pcn_downloads/PCN20221202%20Remove%20Hall%20Sensor%20from%20ESP32%20Series%20of%20Documentation.pdf PCN20221202] gives the following reason for removal: "In the documentation for ESP32 series of products, hall sensor is listed as one of the supported peripherals. However, the hall sensor on ESP32 does not work properly. Therefore, all references to hall sensor in ESP32 documentation need to be removed." </ref>

=== Two-wire interface ===
Hall sensors normally require at least three [[Lead (electronics)|pins]] (for power, ground, and output). However, two-wire ICs only use a power and ground pin, and instead communicate data using different current levels. Multiple two-wire ICs may operate from a single supply line, to further reduce wiring.<ref>{{Cite web |last=Burdette |first=Eric |date=2021-07-08 |title=AN296233: TWO-WIRE AND THREE-WIRE SENSOR INTERFACES |url=https://www.allegromicro.com/-/media/files/application-notes/an296233-two-and-three-wire-sensor-interfaces.pdf |website=[[Allegro MicroSystems]]}}</ref>

=== Human interface devices ===
Hall effect switches for [[computer keyboards]] were developed in the late 1960s by Everett A. Vorthmann and Joseph T. Maupin at [[Honeywell]].<ref>{{cite book |last1=Vorthmann |first1=Everett A. |title=Proceedings of the May 14-16, 1969, spring joint computer conference on XX - AFIPS '69 (Spring) |last2=Maupin |first2=Joseph T. |date=May 1969 |isbn=9781450379021 |pages=149–159 |chapter=Solid state keyboard |doi=10.1145/1476793.1476823 |chapter-url=https://dl.acm.org/citation.cfm?doid=1476793.1476823 |s2cid=7540281}}</ref> Due to high manufacturing costs these keyboards were often reserved for high-reliability applications such as aerospace and military. As mass-production costs have declined, an increasing number of consumer models have become available.

Hall effect sensors can also be found on some high-performance gaming [[Computer keyboard|keyboards]] (made by companies such as [[SteelSeries]], Wooting, [[Corsair Gaming|Corsair]]). With the switches themselves containing magnets.<ref>{{Cite web |title=Guide to keyboards with Hall Effect switches |url=https://www.hlplanet.com/keyboards-hall-effect-switches/ |access-date=2023-11-19 |website=hlplanet.com |language=en}}</ref>

Although [[Sega]] pioneered the use of Hall effect sensors in their [[Sega Saturn]] 3D controller<ref>{{cite web | url=https://www.theverge.com/2023/1/9/23546851/nyxi-wizard-nintendo-switch-driftless-gamecube-controller-hall-effect | title=A GameCube-style Switch controller without stick drift (Thank god) | date=9 January 2023 }}</ref> and [[Dreamcast]] stock controller<ref>{{cite web | url=https://www.windowscentral.com/gaming/what-is-a-hall-effect-controller-anyway-and-do-i-really-need-one | title=What is a Hall Effect controller anyway, and do I really need one? | date=28 July 2023 }}</ref> from the 1990s, Hall effect sensors have only started gaining popularity for use in consumer [[game controller]]s since the early-2020s, most notably in [[analog stick]]/[[joystick]] and trigger mechanisms,<ref>{{cite web |title=Game controllers with hall effect joystick sensors |url=https://www.hlplanet.com/controller-hall-effect-joystick/ |access-date=26 July 2023 |website=hlplanet.com}}</ref> for enhanced experience due to their contactless, high-resolution, low-latency measurements of position and movement and their longer lifespan due to lack of mechanical parts.

Applications for Hall effect sensing have also expanded to industrial applications, which now use Hall effect [[Joystick#Industrial applications|joysticks]] to control hydraulic valves, replacing the traditional mechanical levers with contactless sensing. Such applications include mining trucks, backhoe loaders, cranes, diggers, scissor lifts, etc.

=== Dual Hall sensor ICs ===
Some ICs include two Hall elements. This is useful for counting a series of increments (an [[incremental encoder]]) to make a [[Linear encoder|linear]] or [[rotary encoder]], whereby a moving or rotating arrangement of magnets produces an alternating magnetic pattern sensed as a [[quadrature encoder|quadrature encoded]] pattern.<ref name=":0" /> That pattern can then be decoded to provide both the speed and direction of movement, or simply counted up and down to determine the position or angle. (When only one Hall element is used, direction of linear or rotary encoders cannot be determined). The two elements placed at a precise distance apart from each other on the [[Die (integrated circuit)|die]] may either be oriented in the same direction,<ref>{{Cite web |title=Dual Hall-effect latch IC with speed and direction - Medium sensitivity |url=https://www.melexis.com/en/product/MLX92251/Dual-Hall-Effect-Latch-Speed-Direction |access-date=2023-12-28 |website=Melexis |language=en}}</ref> in which case the magnetic pole-to-pole pitch should ideally be two times the Hall element-to-element pitch.<ref name=":0" /> Alternatively, the Hall elements may be oriented at 90 degrees to provide sensing in two axes.<ref>{{Cite web |title=Dual Hall-Effect Latches {{!}} Allegro MicroSystems |url=https://www.allegromicro.com/en/products/sense/switches-and-latches/dual-hall-effect-latches |access-date=2023-12-28 |website=www.allegromicro.com}}</ref><ref>https://www.ti.com/lit/ds/symlink/tmag5111.pdf {{bare URL PDF|date=March 2024}}</ref>

== See also ==

* [[Reed switch]]

== References ==

{{refs}}

== Further reading ==

* {{ cite journal|first1=A.|last1=naveed|first2=T.|last2=Ihn|first3=K.|last3=Ensslin|first4=G.|last4=Papp|first5=F.|last5=Peeters|first6=K.|last6=Maranowski|first7=A. C.|last7=Gossard|title=Classical Hall effect in scanning gate experiments|journal=[[Phys. Rev. B]]|volume=74|number=16|page=165426|date=2006|doi=10.1103/PhysRevB.74.165426|bibcode=2006PhRvB..74p5426B|hdl=10067/613600151162165141|s2cid=121163404|url=https://repository.uantwerpen.be/docman/irua/df27b2/61360.pdf |hdl-access=free}}
* {{ cite web |last1=Nave |first1=R |title=Hall Effect |url=http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/Hall.html |website=Hyperphysics |publisher=Georgia State University Department of Physics and Astronomy |access-date=20 April 2021}}

== External links ==

* {{commonscat-inline|Hall sensors}}

[[Category:Magnetic devices]]
[[Category:Position sensors]]
[[Category:Transducers]]