What is the measurement principle of the open loop Hall current sensor?

The open-loop Hall current sensor is based on the principle of the Hall effect. In addition to the principle of the Hall effect, there are also fluxgate technology and magnetoresistance technology to measure current. In principle, the fluxgate technology has higher measurement accuracy than the Hall effect principle, and is usually used in the development of high-precision laboratory current sensors and other measuring instruments. The current sensor based on the Hall effect principle is mainly introduced here, so let's learn about the measurement principle of the open-loop Hall current sensor!

Classification of open-loop Hall current sensors:

Open-loop Hall current sensors are divided into two measurement methods, open-loop Hall current sensors and closed-loop Hall current sensors. These two types of sensors have one more coil than the open-loop sensor in the structure, and the closed-loop sensor is better than the open-loop sensor in terms of accuracy.

The measurement principle of the open-loop Hall current sensor:

The open-loop Hall current sensor is composed of important components such as magnetic core, Hall chip, and operational amplifier. When the current flows in the iron core, a magnetic field is induced in the iron core, the iron core concentrates the magnetic field at the cutout, and the corresponding voltage is induced in the Hall element. The voltage is processed by the operational amplifier and output, and the output voltage of the operational amplifier The signal and the primary side current satisfy a certain linear relationship, so the voltage signal is sampled by the single-chip microcomputer, and the magnitude of the measured current is calculated, which plays the role of measuring the current. Open-loop Hall current sensors are also known as direct measurement. Due to the limited size, many chip-level Hall current chips use the open-loop measurement principle, such as ACS712, ACS758, etc.

The working principle of the open-loop Hall current sensor:

There is one more compensation coil, and its coil is wound on the iron core. After the current sensor passes through the iron core, a magnetic field is induced in the iron core, and the Hall element converts the magnetic field into a voltage. After the voltage is processed by the operational amplifier, the drive circuit generates a compensation current, and the compensation current flows to the coil to generate a magnetic field. The magnetic field and the primary side The magnitude of the magnetic field generated by the current is equal. Therefore, the compensation current scales the primary side current, and the scaling ratio has a linear relationship with the number of turns of the compensation coil. Closed-loop Hall current sensors are also known as indirect measurement methods.

Key Parts-Hall Parts

In the open-loop Hall current sensor, the Hall component is an important component, and its performance will affect the performance of the product. The function of the Hall element is to convert the magnetic flux within a certain range into a voltage signal. As shown in the figure below, the Hall element converts the magnetic flux density within 50mT into a voltage signal. Therefore, when selecting this chip, the magnetic flux density generated by the iron core should not exceed 50mT.

The main component-magnetic core

Open-loop Hall current sensor is a product whose structure and circuit are closely matched, in which the height, position, material, length and cross-sectional area of ​​the Hall component determine the performance of the product. When designing the product, attention should be paid to strictly calculating the magnetic path length of the iron core, the cross-sectional area of ​​the iron core, the magnetic gap interval and the height of the Hall chip according to the measurement range. Of course, this part of the calculation is the core part of the Hall current sensor design.

The above is what the measurement principle of the open-loop Hall current sensor is. If you want to know more, please feel free to contact us!