In recent years, due to the development of power electronic devices and the application of new technologies such as frequency conversion, inverter, and chopper, the waveforms of voltage and current are no longer standard sine waves or DC. The traditional transformer is obviously not suitable for the measurement of this waveform. Therefore, many countries have successively carried out the research and development of non-contact current and voltage sensors, especially Hall current and voltage sensors are regarded as the representative of this technology.
Hall sensor is suitable for isolation and conversion of complex signals such as AC, DC and pulse. Through the principle of Hall effect, the converted signal can be directly collected and accepted by various acquisition devices such as AD, DSP, PLC, and secondary instruments. Small size, long life, easy installation, fast response time, wide current measurement range, high accuracy, strong overload capacity, good linearity, and strong anti-interference ability.
1) HALL open-loop current sensor
★ Technical features:
(1) Small volume
(2) Wide measuring range
(3) Light weight
(4) Low power consumption
(5) No insertion loss
★ Working principle:
After the magnetic field generated by the primary current IP is concentrated through the magnetic core, the HALL induction chip is used to induce the size and direction of the primary current IP at the air gap of the magnetic core. The output voltage of the HALL induction chip passes through the signal processing circuit, so that the output of the sensor can accurately reflect the magnitude of the measured current. In order to improve the performance of the HALL open-loop sensor, silicon steel or permalloy is usually used as the material of the magnetic core. When the operating frequency of the measured current is greater than 10kHz for a long time, the sensor may be damaged by the heating of the magnetic core.
2) HALL closed-loop current sensor
★ Technical features:
(1) Bandwidth
(2) High measurement accuracy
(3) Fast response
(3) Low-temperature drift
(4) very good nonlinear distortion
(5) No insertion loss
★ working principle:
The magnetic field generated by the primary current IP and the magnetic field generated by the output current IS on the compensation coil are equal in magnitude and opposite in direction. The HALL induction device and processing circuit together with the compensation coil, output the current IS, and the output current IS accurately reflects the magnitude and direction of the measured current. Since the magnetic core works in the state of zero magnetic flux, the non-linearity and remanence of the magnetic core have no influence on the accuracy of the sensor, so the HALL closed-loop sensor has high accuracy and small nonlinear distortion.
| Type | Open-loop Split Type | Open-loop Closed Type | Close-loop |
| Accuracy | 1 Grade | 1 Grade | 0.5 Grade |
| Input Current | 20A-20000A | 20A-20000A | 10A-20000A |
| Output Signal | 4-20mA, 4V/5V | 4-20mA, 4V/5V | 50,100,200,400mA |
| Advantage | low cost easy to install | low cost easy to install | Quick response ≤1us Wide frequency ≤100kHz |
| Disadvantage | low accuracy | low accuracy | large volume large power consumption high cost |
