Hall current sensors are based on the magnetic balance Hall principle. According to the Hall effect principle, when a current Ic is passed through 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, an electric 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.
1. Basic Principle of Hall Current Sensor
A Hall effect 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 based on the Hall effect principle, which applies Ampere's law: a magnetic field proportional to the current is generated around a current-carrying conductor, and the Hall device is used to measure this magnetic field. This makes non-contact current measurement possible.
2. Detection principle of 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.
3. Compensation principle of Hall current sensor
The primary circuit has a measured current I1, which 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 a magnetic balance. The Hall effect device is always in a state of detecting zero magnetic flux. Therefore, it is called a Hall magnetic compensation current sensor. This advanced principle is superior to the direct detection principle, with outstanding advantages such as 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.
