A voltage sensor is a device that converts the measured electrical parameters into DC current and DC voltage, and isolates them to output analog or digital signals. Voltage and current sensors are used to measure voltage or current signals with severe waveform distortion in the power grid, and can also measure non sinusoidal waveforms such as square waves and triangular waves. So what is the working principle of a voltage sensor?
Working principle of voltage sensor – Basic working principle
A voltage sensor is a type of sensor that can sense the measured voltage (of different models), convert the obtained voltage into DC current or DC voltage within a certain period of time (material, usage method), and isolate and output analog or digital signals. It is mainly used to measure voltage or current signals with severe waveform distortion in the power grid, and can also measure non sinusoidal waveforms such as square waves and triangular waves. Compared with the traditional transformer and shunt, the voltage sensor has the advantages of high precision, fast response, good linearity, wide frequency band, strong overload and no loss of measuring energy. It has been widely used in power, electronics, inverter devices, switching power supply, AC frequency conversion and speed regulation and many other fields.
When the primary current IP passes through the voltage sensor, magnetic field lines are generated, which are concentrated around the magnetic core. The Hall electrode built into the air gap of the magnetic core can generate a voltage of only a few millivolts proportional to the primary magnetic field lines. The electronic circuit can convert this small signal into a secondary current IS, and the output signal of the voltage sensor is the secondary current IS, which is proportional to the input signal (primary current IP). IS is generally very small, only 100-400mA. If the output current passes through the measuring resistor RM, an output voltage signal of several volts proportional to the primary current can be obtained.
The primary voltage is limited to 10mA by an external or internal resistor. After passing through multiple turns of winding, the magnetic field generated by the primary current is detected by Hall elements in the air gap through a magnetic material, and the corresponding electromotive force is induced. The electromotive force is adjusted by the circuit and fed back to the compensation coil for compensation. The magnetic flux generated by the compensation coil is equal in magnitude and opposite in direction to the magnetic flux generated by the primary current (measured voltage through a current limiting resistor), thus maintaining zero magnetic flux in the magnetic core.
Working principle of voltage sensor – Hall voltage sensor
Hall principle: Hall voltage sensor is a type of sensor that utilizes the Hall effect to limit the current to 10mA by passing the primary voltage through an external or internal resistor. After passing through multiple turns of winding, the magnetic field generated by the primary current is detected by the Hall element in the air gap through a magnetic material, and the corresponding electromotive force is induced. The electromotive force is adjusted by the circuit and fed back to the compensation coil for compensation. The magnetic flux generated by the compensation coil is equal in magnitude and opposite in direction to the magnetic flux generated by the primary current (measured voltage through a current limiting resistor), thus maintaining zero magnetic flux in the magnetic core. In fact, Hall voltage sensors utilize the same technology as magnetic balance closed-loop Hall current sensors, namely zero flux Hall current sensors.
It is a special Hall closed-loop sensor with multiple turns on the primary side, which makes the output signal proportional to the measured voltage. The schematic diagram of the sensor is shown in the above figure. The Hall voltage sensor mainly includes a primary coil, a magnetic ring, a secondary coil, an amplification circuit, and a current limiting resistor R connected in series with the primary coil. Excluding the current limiting resistor R, the remaining part is equivalent to a closed-loop Hall current sensor. Compared to electromagnetic voltage transformers, it has the advantages of small size, light weight, wide bandwidth, and dual-use of AC and DC, and has been widely used in the field of industrial measurement and control.
