Hall devices are a type of magneto electric conversion device made of semiconductor materials. Hall current sensors include open-loop and closed-loop types. Most high-precision Hall current sensors belong to the closed-loop type, which is based on the magnetic balance Hall principle, also known as the closed-loop principle. Today, Weikewei Technology will introduce to you the working principle, measurement methods, and applications of Hall current sensors.

Working principle of Hall current sensor

1. Direct discharge (open-loop) current sensor (CS series)

When the primary current IP flows through a long wire, a magnetic field is generated around the wire, and the magnitude of this magnetic field is proportional to the current flowing through the wire. The generated magnetic field is concentrated in the magnetic ring, measured and amplified by Hall elements in the air gap of the magnetic ring, and its output voltage VS accurately reflects the primary current IP. The general rated output calibration is 4V.

2. Magnetic balance (closed-loop) current sensor (CSM series)

Magnetic balance current sensor, also known as compensation sensor, refers to the compensation of the magnetic field generated by the primary current Ip at the magnetic gathering ring through the magnetic field generated by a secondary coil current. The compensation current Is accurately reflects the primary current Ip, thereby enabling the Hall device to be in the working state of detecting zero magnetic flux.

The specific working process is as follows: when a current passes through the main circuit, the magnetic field generated on the wire is concentrated by the magnetic ring and induced to the Hall device. The generated signal output is used to drive the power transistor and make it conductive, thereby obtaining a compensation current Is. This current then generates a magnetic field through a multi turn winding, which is exactly opposite to the magnetic field generated by the measured current, thus compensating for the original magnetic field and gradually reducing the output of the Hall device. When the magnetic field generated by multiplying Ip with the number of turns is equal, Is no longer increases. At this point, the Hall device acts as an indicator of zero magnetic flux, and Ip can be tested using Is. When Ip changes, the balance is disrupted, and the Hall device outputs a signal, repeating the above process to reach balance again. Any change in the measured current will disrupt this balance. Once the magnetic field loses balance, the Hall device will output a signal. After power amplification, a corresponding current immediately flows through the secondary winding to compensate for the unbalanced magnetic field. The time required from magnetic field imbalance to re equilibrium is theoretically less than 1 μ s, which is a dynamic equilibrium process. Therefore, from a macro perspective, the number of ampere turns of the secondary compensation current is always equal to the number of ampere turns of the primary measured current at any time.

Measurement method of Hall current sensor

1. The primary wire should be placed in the center of the sensor's inner hole and should not be placed off center as much as possible;

2. Fully fill the sensor inner hole with the original wire as much as possible, without leaving any gaps;

3. The current to be measured should be close to the standard rated value IPN of the sensor, without a significant difference. Due to limited conditions, there is only one sensor with a high rated value at hand, and the current value to be measured is much lower than the rated value. To improve measurement accuracy, the primary wire can be wound a few more times to approach the rated value. For example, when using a sensor with a rated value of 100A to measure a current of 10A, in order to improve accuracy, the primary wire can be wound ten times around the center of the sensor's inner hole (generally, NP=1; one circle in the inner hole, NP=2;...; nine circles, NP=10, then NP × 10A=100A is equal to the rated value of the sensor, thereby improving accuracy);

4. When the current value to be measured is IPN/10, high accuracy can still be achieved at 25 ℃.

Application of Hall current sensor

In recent years, high-power transistors, rectifiers, and thyristors have been widely used in automation systems, and AC variable frequency speed regulation and pulse width modulation circuits have been widely adopted, making the circuit no longer just a traditional 50 cycle sine wave, but various different waveforms have emerged. For this type of circuit, traditional measurement methods cannot reflect its true waveform, and current and voltage detection components are not suitable for sensing and detecting medium to high frequency and high di/dt current waveforms.

Hall effect sensors can measure current and voltage of any waveform. The output terminal can truly reflect the waveform parameters of the input terminal current or voltage. In response to the common problem of large temperature drift in Hall effect sensors, compensation circuits are used for control, effectively reducing the impact of temperature on measurement accuracy and ensuring measurement accuracy; It has the characteristics of high precision, easy installation, and low price.

Hall effect sensors are widely used in facilities that require isolation and detection of current and voltage, such as variable frequency speed regulation devices, inverter devices, UPS power supplies, communication power supplies, welding machines, electric locomotives, substations, CNC machine tools, electrolytic plating, microcomputer monitoring, and power grid monitoring.

The above is霍尔电流传感器I believe everyone should have a better understanding of Hall current sensors by explaining their working principles, measurement methods, and applications. Hall current sensors, especially closed-loop Hall current sensors, have been widely used in the field of industrial measurement and control due to their wide bandwidth, dual-use of AC and DC, and resistance to magnetic saturation.