Basic Principles and Detection Principles of Hall Current Sensors

The Hall current sensor is based on the magnetic balance Hall principle. According to the Hall effect principle, a current Ic is introduced into the control current terminal of the Hall element, and a magnetic field with magnetic induction intensity B is applied in the direction normal to the plane of the Hall element. Then, a potential VH, known as the Hall potential, is generated between the directions perpendicular to the current and the magnetic field (i.e., between the Hall output terminals), and its magnitude is proportional to the control current I.

1. Basic Principles of Hall Current Sensors The Hall device is a magnetic-electric conversion device made of semiconductor materials. If a control current IC is passed into the input terminal, and a magnetic field B crosses 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, that is: VH=KHICBsinΘ. The Hall current sensor is made according to the Hall effect principle, applying Ampere’s law, which states that a magnetic field proportional to the current is generated around the current-carrying conductor, and the Hall device is used to measure this magnetic field. Therefore, non-contact measurement of current becomes possible.

2. Detection Principles of Hall Current Sensors Since there is a good linear relationship between the magnetic circuit and the output of the Hall device, 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 such that when the measured current I1 is at its rated value, U0 equals 50mV or 100mV. This creates a Hall direct detection (no amplification) current sensor.

3. Compensation Principles of Hall Current Sensors The primary circuit has a measured current I1, which will produce a magnetic flux Φ1. The magnetic flux Φ2 generated by the current I2 flowing through the compensation coil on the secondary side compensates for it to maintain magnetic balance. The Hall device is always in the role of detecting zero magnetic flux. Therefore, it is called a Hall magnetic compensation current sensor. This advanced principle mode is superior to the direct detection principle mode, with outstanding advantages such as fast response time and high measurement accuracy, especially suitable for detecting weak currents. It is known that: Φ1=Φ2, I1N1=I2N2, I2=NI/N2·I1. When the compensation current I2 flows through the measurement resistance RM, it is converted into voltage across RM. As the sensor measures the voltage U0, that is: U0=I2RM. The rated input from ~ series specifications of current sensors is made according to the Hall magnetic compensation principle. Since the magnetic compensation current sensor must wind thousands of turns of compensation coil around the magnetic ring, the cost increases; secondly, the working current consumption also increases accordingly; however, it has incomparable advantages over direct detection types, such as higher accuracy and faster response.