Hall sensor is the world’s third largest sensor product, it is widely used in industry, automobile industry, computer, mobile phone and emerging consumer electronics. In the next few years, as more and more automotive electronics and industrial design companies move to China, the annual sales of Hall sensors in the Chinese market will maintain a high growth rate of 20% to 30%.

Hall sensor is the world’s third largest sensor product, it is widely used in industry, automobile industry, computer, mobile phone and emerging consumer electronics.

In the next few years, as more and more automotive electronics and industrial design companies move to China, the annual sales of Hall sensors in the Chinese market will maintain a high growth rate of 20% to 30%.

At the same time, the related technologies of Hall sensors are still being improved, and programmable Hall sensors, intelligent Hall sensors and miniature Hall sensors will have better market prospects.

What is the Hall Effect?

The Hall effect is a kind of magnetoelectric effect, which was discovered by Hall (AHHall, 1855-1938) in 1879 when he studied the conductive mechanism of metals.

Later, it was found that semiconductors, conductive fluids, etc. also have this effect, and the Hall effect of semiconductors is much stronger than that of metals. When the current passes through the conductor perpendicular to the external magnetic field, the carriers are deflected, and the direction perpendicular to the current and the magnetic field will produce a The addition of an electric field results in a potential difference between the two ends of the conductor. This phenomenon is called the Hall effect. This potential difference is also called the Hall potential difference. The Hall effect should be judged using the left-hand rule.

The most complete dry goods: the advantages, uses and prospects of Hall sensors

The most complete dry goods: the advantages, uses and prospects of Hall sensors

In formula (1): if the control current Ic is kept unchanged, under certain conditions, the magnitude of the magnetic induction can be calculated by measuring the Hall voltage, thereby establishing the connection between the magnetic field and the voltage signal. According to this relationship, A semiconductor device for measuring magnetic fields, the Hall element, has been developed.

The essence of the Hall effect is that when the carriers in a solid material move in an external magnetic field, the trajectory is shifted due to the action of the Lorentz force, and charges are accumulated on both sides of the material, forming a direction perpendicular to the current. Finally, the Lorentz force on the carriers is balanced with the repulsive force of the electric field, thereby establishing a stable potential difference, which is the Hall voltage, on both sides.

The ratio of the orthogonal electric field and the product of the current strength and the magnetic field strength is the Hall coefficient. The ratio of the parallel electric field to the current intensity is the resistivity. A large number of studies have revealed that not only negatively charged electrons but also positively charged holes participate in the conductive process of materials.

What is a hall sensor?

Hall sensor is a magnetic field sensor made according to the Hall effect, which is widely used in industrial automation technology, detection technology and information processing.

The Hall coefficient measured by the Hall effect experiment can determine important parameters such as the conductivity type, carrier concentration and carrier mobility of the semiconductor material.

Since the potential difference generated by the Hall element is very small, the Hall element is usually integrated with the amplifier circuit, the temperature compensation circuit and the regulated power supply circuit on a chip, which is called a Hall sensor. Hall sensors, also known as Hall ICs, have a smaller shape, as shown in the following figure:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

Advantages and uses of Hall sensors

Many people know that the higher the degree of automation in the car, the more microelectronic circuits, the more afraid of electromagnetic interference. In the car, there are many lamps and electrical devices, especially the high-power headlights, air conditioner motors and wiper motors will generate inrush current when switching, which will cause arcing of the mechanical switch contacts, resulting in large electromagnetic interference. Signal.

These phenomena can be reduced by using a power Hall switch circuit. By detecting the change of the magnetic field, the Hall device converts it into an electrical signal output, which can be used to monitor and measure the changes of the operating parameters of various parts of the car.

For example, position, displacement, angle, angular velocity, rotational speed, etc., and these variables can be transformed twice; pressure, mass, liquid level, flow rate, flow rate, etc. can be measured. The output of the Hall device is directly interfaced with the Electronic control unit, which can realize automatic detection.

The current Hall devices can withstand a certain vibration, can work in the range of minus 40 ℃ to 150 ℃ above zero, all sealed from water and oil pollution, can fully adapt to the harsh working environment of the car.

Hall sensors can measure current and voltage of arbitrary waveforms, such as DC, AC, pulse waveforms, etc., and even measure transient peaks. The secondary side current faithfully reflects the waveform of the primary side current.The ordinary transformer is incomparable, it is generally only suitable for measuring 50Hz sine wave

There is good electrical isolation between the primary side circuit and the secondary side circuit, and the isolation voltage can reach 9600Vrms;

High accuracy: the accuracy is better than 1% in the working temperature range, which is suitable for the measurement of any waveform; the Hall switch device has no contact, no wear, clear output waveform, no jitter, no bounce, and high position repeatability ( up to μm level).

Wide bandwidth: The rise time of a high-bandwidth current sensor can be less than 1μs; however, the voltage sensor has a narrow bandwidth, generally within 15kHz, and a 6400Vrms high-voltage voltage sensor has a rise time of about 500uS and a bandwidth of about 700Hz.

Wide measurement range: current measurement up to 50KA, voltage measurement up to 6400V.

Solid structure, small size, light weight, long life, easy installation, low power consumption, high frequency (up to 1MHZ), vibration resistance, not afraid of dust, oil, water vapor and salt spray pollution or corrosion.

The most complete dry goods: the advantages, uses and prospects of Hall sensors

The picture above is a typical Hall sensor implementation of positioning application – two magnets on a wheel pass through the Hall effect sensor. In the wheel pictured, with two equally spaced magnets, the voltage on the sensor will peak twice in a cycle.

Often used to measure wheel and axle speed, for example in combustion engine ignition timing (timing) or on tachometers. Its use in brushless DC motors is used to detect the position of permanent magnets.

Hall sensors are widely used in variable frequency speed control devices, inverter devices, UPS power supplies, communication power supplies, electric welding machines, electric locomotives, substations, CNC machine tools, electrolytic plating, microcomputer monitoring, power grid monitoring and other facilities that require isolation and detection of current. solar energy, wind energy and subway track signal, automotive electronics and other fields.

Main characteristic parameters of Hall sensor

As mentioned earlier, the Hall sensor is a magnetic field sensor made according to the Hall effect. Its main characteristic parameters are as follows.

(1) Input resistance R

The DC resistance of the two excitation current terminals of the Hall sensor element is called the input resistance. Its value ranges from a few ohms to a few hundred ohms, depending on the type of component.

As the temperature increases, the input resistance becomes smaller, so that the input current becomes larger, which eventually causes the potential change of the Hall sensor. In order to reduce this effect, it is best to use a constant current source as the excitation source.

(2) Output resistance R

The resistance between the potential output terminals of the two Hall sensors is called the output resistance, and its digits are of the same order of magnitude as the input resistance. It also changes with temperature. Selecting an appropriate load resistance is easy to match, and the drift of the water potential caused by temperature can be minimized.

(3) Maximum excitation current I—Hall sensor parameters

Since the potential of the Hall sensor increases with the increase of the excitation current, it is always desirable to use a larger excitation current of 1M in the application, but the excitation current increases, the power consumption of the Chenger element increases, and the temperature of the element increases. As a result, the temperature drift of the Hall sensor potential is increased, so the corresponding maximum excitation currents are specified for several parts of each model, and its value ranges from a few milliamps to several hundreds of milliamps.

(4) Sensitivity K

Sensitivity KH=EH/IB, its value is about 10MV (MA.T).

(5) Maximum magnetic induction intensity BM—Hall sensor parameters

When the magnetic induction intensity exceeds BM, the nonlinear error of the potential of the Hall sensor will increase significantly, and the Tes (T) will become several thousand Gauss (Gs) (1Gs=104T).

(6) Equipotentials

At rated excitation current F, when the applied magnetic field is zero, it is an error due to the geometric asymmetry of the 4 poles.

(7) Hall sensor potential temperature coefficient

The value of 6M is generally the open-circuit voltage between the output terminals of the zero-point knife Hall sensor called unequal potential. When using, the bridge method is often used to compensate for the unequal potential caused by a certain magnetic induction intensity and excitation current. When the temperature changes by 1 degree Celsius, the percentage of the potential change of the Hall sensor is weak as the temperature coefficient of the Hall sensor potential, which is related to the material of the Hall sensor element.

Classification of Hall Sensors

Hall sensors are divided into linear Hall sensors and switching Hall sensors.

1) Linear Hall sensor consists of Hall element, linear amplifier and emitter follower, which outputs analog quantity.

The most complete dry goods: the advantages, uses and prospects of Hall sensors

2) The switch-type Hall sensor is composed of a voltage regulator, a Hall element, a differential amplifier, a Schmitt trigger and an output stage, which outputs digital quantities.

The most complete dry goods: the advantages, uses and prospects of Hall sensors

According to the nature of the detected objects, their applications can be divided into direct application and indirect application. The former is to directly detect the magnetic field or magnetic properties of the detected object itself, and the latter is to detect the artificially set magnetic field on the detected object.

Application of Hall sensor in various fields

According to the nature of the detected objects, their applications can be divided into direct applications and indirect applications. The former is to directly detect the magnetic field or magnetic characteristics of the detected object itself, and the latter is to detect the artificially set magnetic field on the detected object, and use this magnetic field as the carrier of the detected information. physical quantity.

For example, force, torque, pressure, stress, position, displacement, speed, acceleration, angle, angular velocity, number of revolutions, rotational speed, and the time when the working state changes, etc., are converted into electricity for detection and control.

(1) Linear Hall sensors are mainly used for the measurement of some physical quantities.

1. current sensor:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

Since there is a magnetic field inside the energized solenoid, and its magnitude is proportional to the current in the wire, the Hall sensor can be used to measure the magnetic field to determine the magnitude of the current in the wire.

Using this principle, a Hall current sensor can be designed. The advantage is that it does not make electrical contact with the circuit under test, does not affect the circuit under test, and does not consume the power of the power supply under test, and is especially suitable for high current sensing.

The working principle of the Hall current sensor is shown in the figure:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

The standard ring iron core has a gap, and the Hall sensor is inserted into the gap, and the ring is wound with a coil. When the current passes through the coil, a magnetic field is generated, and the Hall sensor has a signal output.

2. Displacement measurement:

as the picture shows:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

The two permanent magnets are placed opposite to each other with the same polarity, and the linear Hall sensor is placed in the middle, and its magnetic induction intensity is zero. This point can be used as the zero point of displacement. When the Hall sensor is displaced on the Z axis by △Z, the sensor has A voltage output, the magnitude of the voltage is proportional to the magnitude of the displacement distance.

If the parameters such as tension and pressure are changed into displacement distance, the magnitude of tension and pressure can be measured. It is a torque sensor made according to this principle.

(2) Switch-type Hall sensors are mainly used to measure the number of revolutions, rotational speed, wind speed, flow velocity, proximity switches, door closing informers, alarms, automatic control circuits, etc.

1. To measure the speed or number of revolutions:

As shown below:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

A piece of magnetic steel is glued on the edge of the disc of non-magnetic material, and the Hall sensor is placed near the edge of the disc. When the disc rotates once, the Hall sensor outputs a pulse, so that the number of revolutions (counter) can be measured. Into the frequency meter, the speed can be measured. ?

If the switch-type Hall sensor is regularly arranged on the track according to the predetermined position, when the permanent magnet mounted on the moving vehicle passes through it, the pulse signal can be measured from the measuring circuit. According to the distribution of the pulse signal, the speed of the vehicle can be measured.

2. Various practical circuits:

Switch-type Hall sensors are small in size, wide in operating voltage range, reliable in operation, and cheap in price, so they are widely used.

An example is given below:

Car door status Display:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

Cars now generally have this feature. The Hall sensor is used here, as long as a small permanent magnet is configured, it is easy to make an indicator of whether the door is closed. The configuration circuit is shown as follows:

The most complete dry goods: the advantages, uses and prospects of Hall sensors

Three switch-type Hall sensors are installed on the four door frames of the car, respectively, and a magnet steel is fixed at the appropriate position of the door. When the door is open, the magnet steel is far away from the Hall switch, and the output terminal is high. If one of the four gates is not closed, the output of the NOR gate is low, and the red light is on, indicating that there are still gates that are not closed. If all three gates are closed, the output of the NOR gate is high. , the green light is on, indicating that the door is closed, and the driver can drive with confidence.

Hall Sensor Outlook

The growth rate of Hall sensors in the Chinese market is double digits, and Hall sensors are widely used in our daily life. For example, in a flip or sliding cell phone, the device used to detect the flipping or sliding of the cell phone cover is a Hall sensor; for another example, on a computer keyboard, the scroll key for moving the cursor is composed of Hall sensors ; Also, Hall sensors are also used in components that require motors, such as automotive gearboxes and electric doors and windows. We deal with Hall sensors in our everyday lives.

Hall sensors are used in different fields, so each market has different requirements for it. The main requirements for Hall sensors in the mobile phone market include size, power consumption, and adjustable thresholds. In industrial and automotive applications, Hall sensors must first meet the requirements of the device for industrial or automotive certification, such as the appropriate level of safety, stability and temperature range.

With the continuous development of these terminal application products, Hall sensors also show the development of miniaturization, high integration, high sensitivity and temperature resistance.

The Links:   NL10276BC20-18B LTA084C190F