Hall sensors application. Current transformers - the right solution

Modern current sensors are classified into the following types:
- resistive sensors (current shunts);
- Hall effect current sensors;
- current transformers;
- fiber-optic current sensors (FOCS) based on the Faraday effect;
- Rogovsky belt;
- current clamp
Each has its own advantages and disadvantages, which limit the scope of its application.

Yes

	Current sense resistors	Current transformers	Hall sensors
Measured current	Constant	Variable	Constant and variable
Measured current range	Up to 20 A	Up to 1000A	Up to 1000A
Measurement error	1%	5%	10%
Galvanic isolation	No	there is	there is
Insertion loss	there is	there is	No
frequency range	100 kHz	50/60/400 Hz	200 kHz
Relative cost	low	high	average
Requires external power supply	No	No

The main disadvantage of a resistive current sensor is the need to connect the sensor directly to the measurement circuit. The main disadvantage of a current transformer is that it only measures AC currents at power frequency. The Hall effect current sensor has a number of advantages, which are the ability to measure both DC and AC currents, and small size. Their main advantages include the absence of power losses introduced from the system, a wide frequency range. The disadvantages are the need for an external power supply and temperature dependence.

Allegro Microsystems current sensors

Allegro Microsystems specializes in the design and manufacture of analog-to-digital power ICs and Hall effect current sensors. For the range of 5-200 A, smart microcircuits are offered, and for the range up to 1000 A and above, linear microcircuits with remote current measurement are offered. The sensors operate in an extended temperature range, which allows them to be used in harsh operating conditions.
The main areas of application are automotive and power electronics systems, industrial automation, general-purpose equipment.

Principle of operation

The sensors consist of a very precise linear Hall effect sensor integrated on the chip and a copper conductor placed close to the chip. Electric current, flowing through the conductor, creates a magnetic field, which is detected by the Hall sensor and converted into a voltage proportional to the value of the input current.

Sensor housings

For the production of sensors for 5-200 A, flip chip technology is used, which provides a number of significant advantages for the developer:
- increased sensitivity, the Hall sensor is located very close to the current conductor
- high galvanic isolation, up to 3600 V rms for 60 seconds
- low resistance of the primary circuit, less than 1 mOhm, reduced power losses
- standard housings for surface mounting.

Sensors for a range of 50-200 A are produced in a housing of our own design - CB. This housing includes a copper conductor and an analog Hall sensor and allows to measure direct current up to 200 A and pulsed up to 1200 A. The sensors are calibrated during production, withstand breakdown voltage up to 4800 V rms for 60 seconds, provide insulation up to 700 V and reinforced insulation up to 4500 B. Conductor resistance is 100mΩ, so the IC has ultra-low power loss when measuring maximum current.

Thermal compensation

The current sensors use a patented digital temperature compensation technology that can significantly improve both the sensitivity and output voltage error at the operating point. Both parameters are measured at the stage of final testing in two modes: at room temperature and at 85 ... 150 ° C. This data is stored in EEPROM memory. As a result, Allegro sensors have a total error of ± 1% in the range of 25 ... 150 ° С. This late-stage calibration eliminates the need for post-PCB temperature calibration.

Application of current sensors in an electric drive

Allegro current sensors can be used in several drive units due to their galvanic isolation and good dV / dt speed parameters.
They can be used to measure DC bus current (1), phase current (2) or low level current.

Galvanic isolation allows Allegro sensors to be used to measure motor phase current directly. This simplifies the control unit and reduces noise. The ACS710, ACS711 and ACS716 sensors have error outputs that can be used to detect short circuits or other phenomena caused by high current.
The main current sensors for the electric drive:

Current sensors in power amplifiers

Correct control of the power amplifier in a base station or portable radio is the basis for the correct trade-off between power output and efficiency.
Bias current is a key control parameter in most output stages, so Allegro offers several current sensors for this task.

ACS711	100 kHz current sensor in QFN / SOIC housing
ACS712	80 kHz current sensor in SOIC housing

Benefits of Allegro current sensors

- the ability to measure direct current, alternating current and their combinations;
- low energy losses and, as a result, low heat generation, reduced dimensions and the ability to control large currents;
- built-in galvanic isolation

High accuracy, galvanic isolation of the measuring circuit, thermal stability and small dimensions make the sensors a good solution for use in converter technology, household, automotive and industrial electronics.

Sensors 0-50 A

3000 SOICW-16ACS716

Series	Sensor type	Power supply, V	Measurement range, A	Isolation voltage, Vrms	Bandwidth, kHz	Pace. range*	Type of shell
ACS709	Bidirectional	3.3, 5	± 12 to 75	2100	120	L	QSOP-24
ACS710	Bidirectional	5	± 12 to 75	120	K
ACS711	Bidirectional	3.3	± 12.5 to 25	<100 В пост.тока	100	E, K	SOIC-8, QFN-12
ACS712	Bidirectional	p> 5	± 5 to 30	2100	80	E	SOIC-8
ACS713	One-way	5	20 to 30	2100	80	E	SOIC-8
ACS714	Bidirectional	5	± 5 to 30	2100	80	E, L	SOIC-8
ACS715	One-way	5	20 to 30	2100	80	E, L	SOIC-8
Bidirectional	3.3	± 75	3000	120	K	SOICW-16
ACS717	Bidirectional	3.3	± 10 to 20	4800	40	K	SOICW-16
ACS718	Bidirectional	6	± 10 to 20	4800	40	K	SOICW-16
ACS764	One-way	3.3	16 or 32	<100 В пост.тока	2	X	QSOP-24

Current sensors 50-200 A

* Symbol for temperature range:
E = -40 ... 85 ° C
K = -40 ... 125 ° C
L = -40 ... 150 ° C
S = -20 ... 85 ° C

Notation system
ACS758 L CB TR -100 B-PFF-T
1 2 3 4 5 6 7
1. Series
2. Temperature range:
E = -40 ... 85 ° C
K = -40 ... 125 ° C
L = -40 ... 150 ° C
S = -20 ... 85 ° C
3. Case type:
SV - building SV
LC - SOIC-8
4. Packing:
not indicated. - in a pencil case
TR - on tape
5. Range of measured current, A
6. Sensor type: B - bidirectional, U - unidirectional
7. Modification of the housing for 50-200A sensors, consists of a 3-letter designation:
The first letter is a plastic case
Second letter - current conductor, S - straight, F - curved
Third letter - leads, S - straight lines, F - angular

Additional Information

Hello everyone!

Perhaps it is worth introducing myself a little - I am an ordinary circuit engineer who is also interested in programming and some other areas of electronics: DSP, FPGA, radio communication and some others. Recently, I plunged headlong into SDR receivers. At first I wanted to devote my first article (hopefully not the last) to some more serious topic, but for many it will become just reading and will not be useful. Therefore, the topic was chosen as a highly specialized and exclusively applied one. I also want to note that, probably, all articles and questions in them will be considered more from the side of the circuitry, and not a programmer or anyone else. Well, let's go!

Not so long ago, I was ordered to design a "Residential building energy monitoring system", the customer is engaged in the construction of country houses, so some of you may have even seen my device. This device measured the consumption currents at each input phase and voltage, simultaneously sending data over the radio channel to the already installed Smart Home system + was able to cut down the starter at the entrance to the house. But the conversation today will not be about him, but about his small, but very important component - the current sensor. And as you already understood from the title of the article, these will be "contactless" current sensors from the Allegro company - ACS758-100.
________________________________________________________________________________________________________________________

You can look at the datasheet on which I will talk about the sensor. As you might guess, the number "100" at the end of the marking is the limit current that the sensor can measure. Frankly, I have doubts about this, it seems to me that the conclusions simply will not withstand 200A for a long time, although it is quite suitable for measuring the inrush current. In my device, a 100A sensor continuously passes at least 35A + through itself without any problems + there are consumption peaks up to 60A.

Figure 1 - External view of the ACS758-100 (50/200) sensor

Before moving on to the main part of the article, I suggest that you familiarize yourself with two sources. If you have basic knowledge of electronics, then it will be redundant and feel free to skip this paragraph. For the rest, I advise you to go for a run for general development and understanding:

1) Hall effect. Phenomenon and working principle
2) Modern current sensors
________________________________________________________________________________________________________________________

Well, let's start with the most important thing, namely the marking. I buy components 90% of the time at www.digikey.com. Components arrive in Russia in 5-6 days, the site has probably everything, also a very convenient parametric search and documentation. So a complete list of family sensors can be viewed there upon request " ACS758". My sensors were bought in the same place - ACS758LCB-100B.

Inside the datasheet on marking everything is painted, but I will still pay attention to the key point " 100V":

1) 100 - this is the measurement limit in amperes, that is, my sensor can measure up to 100A;
2) "V"- this letter is worth paying special attention to, instead of it there may also be a letter" U". Sensor with letter B knows how to measure alternating current, and therefore direct current. Sensor with letter U can only measure direct current.

Also at the beginning of the datasheet there is an excellent sign on this topic:


Figure 2 - Types of current sensors of the ACS758 family

Also, one of the most important reasons for using such a sensor was - galvanic isolation... Power pins 4 and 5 are not electrically connected to pins 1,2,3. In this sensor, communication is only in the form of an induced field.

Another important parameter appeared in this table - the dependence of the output voltage on the current. The beauty of this type of sensors is that they have a voltage output, and not a current like classic current transformers, which is very convenient. For example, the output of a sensor can be connected directly to the ADC input of the microcontroller and readings can be taken.

My sensor has this value 20 mV / A... This means that when a current of 1A flows through the terminals 4-5 of the sensor, the voltage at its output will increase by 20 mV... I think the logic is clear.

The next moment, what is the output voltage? Considering that the power supply is "human", that is, unipolar, then when measuring alternating current there must be a "reference point". For a given transmitter, this reference point is 1/2 of the supply (Vcc). Such a solution is often the case and it is convenient. When current flows in one direction, the output will be " 1/2 Vcc + I * 0.02V", in another half-cycle, when the current flows in the opposite direction, the output voltage will be narrower." 1/2 Vcc - I * 0.02V". At the output we get a sinusoid, where" zero "is 1 / 2Vcc... If we measure direct current, then at the output we will have " 1/2 Vcc + I * 0.02V", then, when processing the data on the ADC, we simply subtract the constant component 1/2 Vcc and work with true data, that is, with the remainder I * 0.02V.

Now it's time to test in practice what I described above, or rather subtracted from the datasheet. In order to work with the sensor and test its capabilities, I built this "mini-stand":

Figure 3 - Site for testing the current sensor

First of all, I decided to apply power to the sensor and measure its output to make sure that it is taken as "zero" 1/2 Vcc... The connection diagram can be taken in the datasheet, but I, wanting only to get acquainted, did not waste time and sculpt a filtering capacitor for power supply + RC low-pass filter circuit at the Vout pin. In a real device, you can't go anywhere without them! I ended up with the following picture:

Figure 4 - The result of measuring "zero"

When power is applied 5B from my scarves STM32VL-Discovery I saw the following results - 2.38V... The very first question that arose: " Why 2.38 and not those described in datasheet 2.5?"The question disappeared almost instantly - I measured the power bus during debugging, and there is 4.76-4.77V. And the thing is that the power comes from USB, there is already 5V, after USB there is a linear stabilizer LM7805, and this is clearly not an LDO with 40 mV drop. Here on it it is about 250 mV and falls. Well, okay, this is not critical, the main thing is to know that "zero" is 2.38 V. It is this constant that I will subtract when processing data from the ADC.

Now let's take the first measurement, so far only with the help of an oscilloscope. I will measure the short-circuit current of my regulated power supply, it is equal to 3.06A... This and the built-in ammeter shows and the fluke gave the same result. Well, we connect the outputs of the power supply unit to the legs 4 and 5 of the sensor (in the photo I have the vitukha thrown) and see what happened:

Figure 5 - Measurement of the short-circuit current of the PSU

As we can see, the voltage on Vout increased from 2.38V to 2.44V... If you look at the dependence above, then we should have got 2.38V + 3.06A * 0.02V / A, which corresponds to the value of 2.44V. The result corresponds to expectations, at a current of 3A we got an increase to "zero" equal to 60 mV... Conclusion - the sensor is working, you can already work with it using the MK.

Now you need to connect a current sensor to one of the ADC pins on the STM32F100RBT6 microcontroller. The pebble itself is very mediocre, the system frequency is only 24 MHz, but this headscarf has gone through a lot with me and has established itself. I have owned it for probably 5 years already, because it was received for free at a time when ST was handed out to the right and left.

At first, out of habit, I wanted to put an op-amp with a coefficient after the sensor. gain "1", but, looking at the structural diagram, I realized that he was already inside. The only thing worth considering is that at maximum current, the output power will be equal to the sensor power supply Vcc, that is, about 5V, and STM can measure from 0 to 3.3V, so in this case it is necessary to put a resistive voltage divider, for example, 1: 1.5 or 1: 2. My current is scanty, so I will neglect this moment for now. My test device looks like this:

Figure 6 - Putting together our "ammeter"

Also, to visualize the results, I screwed the Chinese display on the ILI9341 controller, since it was lying around at hand, and my hands did not reach it in any way. To write a full-fledged library for him, I killed a couple of hours and a cup of coffee, since the datasheet was surprisingly informative, which is rare for the crafts of Jackie Chan's sons.

Now we need to write a function to measure Vout using the ADC of the microcontroller. I will not tell you in detail, there is already a sea of ​​information and lessons on STM32. So just look:

Uint16_t get_adc_value () (ADC_SoftwareStartConvCmd (ADC1, ENABLE); while (ADC_GetFlagStatus (ADC1, ADC_FLAG_EOC) == RESET); return ADC_GetConversionValue (ADC1);)
Further, to get the results of the ADC measurement in the executable code of the main body or interrupt, you need to register the following:

Data_adc = get_adc_value ();
By pre-declaring the data_adc variable:

Extern uint16_t data_adc;
As a result, we get the data_adc variable, which takes a value from 0 to 4095, since The ADC in STM32 is 12 bit. Next, we need to turn the result "in parrots" into a more familiar form for us, that is, in amperes. Therefore, it is necessary to first calculate the division price. After the stabilizer on the 3.3V bus, my oscilloscope showed 3.17V, did not begin to figure out what it was connected with. Therefore, dividing 3.17V by 4095, we get the value 0.000774V - this is the division price. That is, having received the result from the ADC, for example, 2711, I simply multiply it by 0.000774V and get 2.09V.

In our task, the voltage is only a "mediator"; we still need to translate it into amperes. To do this, we need to subtract 2.38B from the result, and divide the remainder by 0.02 [B / A]. We got the following formula:

Float I_out = ((((float) data_adc * presc) -2.38) /0.02);
Well, it's time to upload the firmware into the microcontroller and see the results:

Figure 7 - The results of measuring data from the sensor and their processing

I measured the circuit's own consumption as seen at 230 mA. Having measured the same with a verified flux, it turned out that the consumption was 201 mA. Well, one decimal place is already very cool. Let me explain why ... The range of the measured current is 0..100A, that is, the accuracy up to 1A is 1%, and the accuracy up to tenths of an ampere is already 0,1%! And please note, this is without any circuitry solutions. I was even too lazy to hang up power filtering conductors.

Now it is necessary to measure the short-circuit current (SC) of my power supply. I twist the handle to the maximum and get the following picture:

Figure 8 - Short-circuit current measurements

Well, actually the readings at the source itself with its own ammeter:

Figure 9 - Value on the BP scale

In fact, it showed 3.09A, but while I was photographing, the vitukha got hot, and its resistance increased, and the current, accordingly, fell, but this is not so scary.

In conclusion, I don't even know what to say. I hope my article will somehow help novice radio amateurs on their difficult path. Perhaps someone will like my presentation of the material, then I can continue to periodically write about working with various components. You can express your wishes on the topic in the comments, I will try to take into account.

For the correct, reliable and trouble-free operation of modern products of power and not very electronics, it is very important to correctly determine the magnitudes and forms of both voltages and currents acting in the device. The fate of the project, financial success or failure in operation, and even people's lives can depend on the choice of such a seemingly simple element as an electric current or voltage meter. One of the most suitable for such measurements (in the future, we will try to use the term "transformation", since LLC "DTiN Laboratory" supports the opinion that sensors, by definition, are not measuring instruments) option are meters whose operation is based on the Hall effect. The advantage of these converters is the absence of energy losses in the controlled circuit, galvanic isolation between the input and output circuits, speed, the ability to operate in a wide range of temperatures and supply voltages, the ability to directly interface with various monitoring and control devices.

The accuracy of Hall effect meters is in the range from 0.2 to 2 percent and depends, first of all, on the circuitry used in the design of the device. They are widely used in various electrical installations, as a rule, in protection, monitoring and control circuits, but, for example, due to a number of restrictions, they are practically never used for commercial metering of electricity. Similar converters of electrical signals can be found in a modern welding machine, and in an elevator control system, and in a car; the work of railway transport is now unthinkable without these devices. Hall effect devices can convert both alternating and direct current. Despite the fact that they are often called "current transformers", this fact is their main difference and advantage.

The Hall effect was discovered more than 130 years ago by the American scientist Edwin Hall during experiments with magnetic fields. Since then, this effect has been described many times in a wide variety of literature. It is based on the appearance of a transverse electrical potential difference in a constant current conductor in a magnetic field.

What you need to pay attention to when choosing a device for measuring indicators

1. Supply voltage. For industrial measuring devices, both bipolar (± 12V, ± 15V, ± 18V, ± 24V.) And unipolar (+5, 12, 24V) power supply are used. Its choice depends both on the capabilities and needs of the developer, and on the conditions for interfacing with control and management units.
2. Conversion accuracy. As we already mentioned, existing meters operating on the Edwin Hall effect have an accuracy of 0.2 to 2 percent, while this parameter is usually determined by how the meter itself is built - according to a direct amplification scheme or compensation, with 100% feedback. As in most cases, a more accurate compensation-type measuring device for the same rated electric current is more expensive than its counterpart, assembled according to a direct amplification scheme, as a rule, it has large dimensions and a definitely higher consumption of electric current from the power source. Its advantages will be not only greater accuracy, which we have already mentioned, but better linearity and noise immunity.
3. Conversion range. Such designs are capable of converting an input signal to a proportional output or corresponding digital signal with amperage ranging from several hundred milliamperes to several thousand amperes. Of course, such a mechanism is 10kA and more, more expensive than its counterpart by 25A.
4. Frame. These units can have various types of housing. There are options for mounting on a PCB, chassis or DIN rail.
5. The temperature at which these modules are able to work properly. Thus, the reduced operating temperature for measuring instruments operating with current and voltage is, as a rule, -40 C, but there are products that remain operable at -50 and even -55C. The increased operating temperature for most modern products reaches + 85C, there are samples that work at + 105C.

Classification of converters according to the construction principle.

1. Direct gain converter. Advantages - compact size, low power consumption, the ability to work with electrical signals from units of amperes to tens of kiloamperes, low price. They are used to work with signals in the frequency range from DC to 25, less often 50 kHz. Conversion error and non-linearity within units of percent. This type of product has a high overload capacity, is relatively inexpensive and compact.
2. Meters with 100% feedback, also known as "compensation" or "zero flux" sensors. As the name implies, its main distinguishing feature is the presence of a loop closed in magnetic flux. Such devices are used to convert the primary signal from hundreds of milliamperes to tens of kiloamperes, of any shape and frequency, ranging from direct current and ending at the level of 100-150-200 kHz. Compensation converters of these signals are distinguished by the best accuracy, linearity, and resistance to external magnetic fields. The conversion range of these instruments is lower than that of direct amplification designs.
3. Voltage sensor. A kind of compensating device of the electrical signal converter device, characterized by the presence of a built-in primary winding with a large number of turns. The voltage is measured by converting a small primary signal (usually at a nominal voltage of 5 or 10 mA, the choice depends on the developer), set by a resistor connected in series with the primary coil, into a proportional output signal. These devices differ in a rather wide range of input voltages, but they have restrictions on the frequency of the input signal, since the primary winding has significant inductance.
4. A relatively new type of converter - integral, is a development of the direct amplification circuit. The advantage is small size, low price. During the time from the moment of their appearance in 1879 to the present day, devices operating on the effect discovered by Edwin Hall have changed very, very noticeably. The accuracy and reliability have increased, the temperature stability has improved significantly, the dimensions and prices of these mechanisms are steadily decreasing. All these improvements have become possible both as a result of the development of technologies in the production of electronic components, and as a result of new requirements for this class of products. More and more use is found in modern life, saturated with electronic and electrical devices.

Modern industry puts forward special requirements for the reliability and stability of the operation of electrical data converters used to monitor the operation and control of complex systems. This makes it necessary to continue to improve the design of devices, improving their technical characteristics, making them more and more reliable, simple and convenient to use.

As a rule, a novice developer goes to extremes, lays down an accuracy of no worse than 0.1%, and a frequency response from 100 kHz, and then for a long time is surprised that the solution proposed to him costs money comparable to the price of half, or even the whole of his development. In most modern applications, due to the improvement of the parameters of power semiconductors, an accuracy of 1-2% is more than enough, and the key factor in choosing converters is reliability and stability of operation, but these issues are not directly related to circuitry and are worthy of separate consideration.

The Hall effect was discovered in 1879 by the American scientist Edwin Herbert Hall. Its essence is as follows (see figure). If a current is passed through a conducting plate, and a magnetic field is directed perpendicular to the plate, then a voltage will appear on the plate in the direction of the transverse current (and the direction of the magnetic field): Uh = (RhHlsinw) / d, where Rh is the Hall coefficient, which depends on the material of the conductor; H is the strength of the magnetic field; I is the current in the conductor; w is the angle between the direction of the current and the magnetic induction vector (if w = 90 °, sinw = 1); d - material thickness.

Due to the fact that the output effect is determined by the product of two quantities (H and I), Hall sensors have a very wide application. The table shows the Hall coefficients for various metals and alloys. Legend: T - temperature; B - magnetic flux; Rh - Hall coefficient in units of m3 / C.

Hall effect proximity switches have been widely used abroad since the early 1970s. The advantages of this switch are high reliability and durability, small dimensions, and the disadvantages are constant energy consumption and relatively high cost.

The principle of operation of the Hall generator

The Hall sensor has a slotted design. On one side of the slot there is a semiconductor through which current flows when the ignition is on, and on the other side - a permanent magnet.

In a magnetic field, a force acts on moving electrons. The force vector is perpendicular to the direction of both magnetic and electric field components.

If you introduce a semiconductor plate (for example, from indium arsenide or indium antimonide) into a magnetic field with induction B, through which an electric current flows, then a potential difference arises on the sides, perpendicular to the direction of the current. Hall voltage (Hall EMF) is proportional to current and magnetic induction.

There is a gap between the plate and the magnet. There is a steel shield in the sensor gap. When there is no screen in the gap, a magnetic field acts on the semiconductor plate and the potential difference is removed from it. If there is a screen in the gap, then the magnetic lines of force are closed through the screen and do not act on the plate; in this case, the potential difference on the plate does not arise.

The integrated microcircuit converts the potential difference created on the plate into negative voltage pulses of a certain magnitude at the sensor output. When the screen is in the gap of the sensor, then there will be voltage at its output, but if there is no screen in the gap of the sensor, then the voltage at the output of the sensor is close to zero.

Much has been written about the Hall effect, this effect is intensively used in technology, but scientists continue to study it. In 1980, the German physicist Klaus von Klitzung studied the work of the Hall effect at ultralow temperatures. In a thin semiconductor plate, von Klitzung smoothly changed the magnetic field strength and found that the Hall resistance changes not smoothly, but in jumps. The magnitude of the jump did not depend on the properties of the material, but was a combination of fundamental physical constants divided by a constant number. It turned out that the laws of quantum mechanics somehow changed the nature of the Hall effect. This phenomenon has been called the integral quantum Hall effect. For this discovery, von Klitzung received the Nobel Prize in Physics in 1985.

Two years after von Klitzung's discovery in the Bell Telephone laboratory (the same one where the transistor was discovered), Stormer and Tsui studied the quantum Hall effect using an exceptionally pure sample of large gallium arsenide made in the same laboratory. The sample was of such a high degree of purity that electrons passed from end to end without encountering obstacles. The experiment of Stormer and Tsui took place at a much lower temperature (almost absolute zero) and with stronger magnetic fields than in the experiment of von Klitzung (a million times more than).

Much to their surprise, Stormer and Tsui discovered a jump in Hall resistance three times greater than that of von Klitzung. Then they found even larger leaps. The result was the same combination of physical constants, but divided not by an integer, but by a fractional number. The charge of an electron is considered by physicists to be a constant, not divisible into parts. And in this experiment, particles with fractional charges, as it were, took part. The effect was called the fractional quantum Hall effect.

A year after this discovery, an employee of the La Flynn laboratory gave a theoretical explanation of the effect. He stated that the combination of ultra-low temperature and powerful magnetic field causes electrons to form an incompressible quantum fluid. But the drawing using computer graphics shows the flow of electrons (balls) piercing the plane. Irregularities in the plane represent the distribution of the charge of one of the electrons in the presence of a magnetic field and the charge of other electrons. If an electron is added to a quantum liquid, then a certain number of quasiparticles with a fractional charge are formed (in the figure this is shown as a set of arrows for each electron).
In 1998 Horst Stormer, Daniel Tsui and Robert Laughlin were awarded the Nobel Prize in Physics. Currently H. Stormer is a professor of physics at Columbia University, D. Tsui is a professor at Princeton University, R. Laughlin is a professor at Stanford University.

Metal (alloy)
Aluminum
Morgan antimony
Chrome tellurium

In 1879, while working on his doctoral dissertation at Johns Hopkins University, the American physicist Edwin Herbert Hall conducted an experiment with a gold plate. He passed a current through the plate, placing the plate itself on the glass, and, in addition, the plate was subjected to the action of a magnetic field directed perpendicular to its plane, and, accordingly, perpendicular to the current.

In fairness, it should be noted that Hall was at that moment dealing with the question of whether the resistance of the coil through which the current flows depends on the presence next to it, and as part of this work, scientists have conducted thousands of experiments. As a result of the experiment with a gold plate, a certain potential difference was found at the lateral edges of the plate.

This tension is called Hall voltage... The process can be roughly described as follows: the Lorentz force leads to the accumulation of a negative charge near one edge of the plate, and a positive one near the opposite edge. The ratio of the emerging Hall voltage to the value of the longitudinal current is a characteristic of the material from which a particular Hall element is made, and this value is called "Hall resistance".

Serves as a fairly accurate method for determining the type of charge carriers (hole or electron) in a semiconductor or metal.

On the basis of the Hall effect, Hall sensors, devices for measuring the magnetic field strength and determining the current in a conductor are now manufactured. Unlike current transformers, Hall sensors make it possible to measure direct current as well. Thus, the fields of application of the Hall effect sensor in general are quite extensive.

Since the Hall voltage is small, it is logical that the Hall voltage is connected to the terminals. To connect to digital nodes, the circuit is supplemented with a Schmitt trigger, and a threshold device is obtained that is triggered at a given level of magnetic field strength. Such circuits are called Hall switches.

Often a Hall sensor is used in tandem with a permanent magnet, and is triggered when the permanent magnet approaches the sensor at a certain predetermined distance.

Hall sensors are quite widespread in brushless, or valve, electric motors (servomotors), where the sensors are installed directly on the stator of the motor and act as a rotor position sensor (RPR), which provides feedback on the position of the rotor, much like a collector in a collector DC motor.

By fixing a permanent magnet on the shaft, we get a simple revolution counter, and sometimes the shielding effect of the ferromagnetic part itself on the magnetic flux from is sufficient. The magnetic flux from which Hall sensors are usually triggered is 100-200 Gauss.

Produced by the modern electronics industry, three-lead Hall sensors have an open-collector n-p-n transistor in their package. Often, the current through the transistor of such a sensor should not exceed 20 mA, therefore, to connect a powerful load, it is necessary to install a current amplifier.

The magnetic field of a conductor with a current is usually not strong enough to trigger a Hall sensor, since the sensitivity of such sensors is 1-5 mV / G, and therefore, to measure weak currents, a conductor with current is wound onto a toroidal core with a gap, and a Hall sensor is already installed in the gap ... So with a gap of 1.5 mm, the magnetic induction will already be 6 Gs / A.