Hall sensors (Hall switches, linear Hall sensors, etc.) are used in applications such as proximity sensors, position and velocity measurement to detect changes in magnetic field strength. A Hall sensor is a magnetic field sensor based on the Hall effect. Components made of semiconductor materials based on the Hall effect are called Hall elements. They have advantages such as sensitivity to magnetic fields, simple structure, small size, wide frequency response, large output voltage variation, and long lifespan. Therefore, they are widely used in measurement, automation, computer, and information technology fields.
Hall current sensors are based on the magnetic balance Hall principle. According to the Hall effect, when a current Ic is applied to the control current terminal of the Hall element, and a magnetic field with magnetic induction intensity B is applied in the normal direction of the Hall element plane, a potential VH will be generated in the direction perpendicular to the current and the magnetic field (i.e., between the Hall output terminals). This potential is called the Hall potential, and its magnitude is proportional to the control current I. A Hall device is a magnetoelectric conversion device made of semiconductor material. If a control current IC is applied to the input terminal, and a magnetic field B passes through the magnetic sensing surface of the device, a Hall potential VH will appear at the output terminal. The magnitude of the Hall potential VH is proportional to the product of the control current IC and the magnetic flux density B, i.e., VH = KHICBsinΘ. Hall current sensors are made according to the Hall effect principle, applying Ampere's law, that is, generating a magnetic field proportional to the current around a current-carrying conductor, and the Hall device is used to measure this magnetic field. Therefore, non-contact current measurement becomes possible.
The detection principle of a Hall current sensor: Because the magnetic circuit and the output of the Hall device have a good linear relationship, the voltage signal U0 output by the Hall device can indirectly reflect the magnitude of the measured current I1, that is: I1∝B1∝U0
We calibrate U0 to be 50mV or 100mV when the measured current I1 is at its rated value. This creates a Hall effect direct detection (no amplification) current sensor.
The compensation principle of a Hall current sensor: A measured current I1 in the primary circuit generates a magnetic flux Φ1. This flux is compensated by the magnetic flux Φ2 generated by the current I2 passing through the secondary compensation coil, maintaining magnetic balance. The Hall device then always detects zero magnetic flux. Therefore, it is called a Hall magnetically compensated current sensor. This advanced principle is superior to the direct detection principle, with outstanding advantages including fast response time and high measurement accuracy, making it particularly suitable for detecting weak currents.
Knowing that: Φ1=Φ2, I1N1=I2N2, I2=NI/N2·I1
When the compensation current I2 flows through the measuring resistor RM, it is converted into a voltage across RM. This voltage, U0, is measured by the sensor, i.e., U0 = I2RM.
Current sensors with rated inputs ranging from ~ series were manufactured based on the Hall magnetic compensation principle.
Because magnetically compensated current sensors require thousands of turns of compensation coil to be wound on a magnetic ring, the cost increases; secondly, the operating current consumption also increases accordingly; however, it has advantages such as higher accuracy and faster response that are incomparable to direct detection types.
Hall effect sensors are divided into two types: linear Hall effect sensors and switch-type Hall effect sensors. Hall effect devices have many advantages: they are robust, small in size, lightweight, long-lasting, easy to install, have low power consumption, high frequency (up to 1MHz), are vibration-resistant, and unaffected by dust, oil, moisture, salt spray, or other contamination or corrosion. Linear Hall effect devices offer high precision and good linearity; switch-type Hall effect devices are contactless, wear-free, produce clear output waveforms without jitter or bounce, and have high position repeatability.
(a) A switch-type Hall sensor consists of a voltage regulator, a Hall element, a differential amplifier, a Schmitt trigger, and an output stage, and outputs a digital value. There is also a special type of switch-type Hall sensor called a key-lock Hall sensor.
(ii) The linear Hall sensor consists of a Hall element, a linear amplifier and an emitter follower, and it outputs an analog signal.
Linear Hall sensors can be further divided into open-loop and closed-loop types. Closed-loop Hall sensors are also known as zero-flux Hall sensors. Linear Hall sensors are mainly used for AC and DC current and voltage measurement.
Hall effect sensor technology has wide applications in the automotive industry, including powertrain, body control, traction control, and anti-lock braking systems. To meet the needs of different systems, Hall effect sensors come in three forms: switch-type, analog, and digital. Hall effect sensors can be made of metals and semiconductors, and the change in the quality of the effect depends on the material of the conductor, which directly affects the positive ions and electrons flowing through the sensor.
In manufacturing Hall effect sensors, the automotive industry typically uses three semiconductor materials: gallium arsenide (GaAs), indium antimonide (IU), and indium arsenide (IU). IU is the most commonly used. The form of the Hall sensor determines the type of amplifier circuit, and its output must be adapted to the controlled device. This output can be analog, such as an accelerator position sensor or throttle position sensor, or digital, such as a crankshaft or camshaft position sensor. When a Hall effect sensor is used as an analog sensor, it can be used in a temperature gauge in an air conditioning system or a throttle position sensor in a powertrain control system.
