Open-loop and close-loop current sensor

Open-loop current sensor
Because there is a magnetic field inside the energized solenoid, its size is proportional to the current in the wire, so the Hall sensor can be used to measure the magnetic field to determine the size of the current in the wire. Using this principle, a Hall current sensor can be designed. The advantage is that it does not make electrical contact with the circuit under test, does not affect the circuit under test, does not consume the power of the power supply under test, and is particularly suitable for large current sensing.
The working principle of the Hall current sensor is shown in Figure 6. The standard ring core has a gap. Insert the Hall sensor into the gap. The ring is wound around the coil. When the current passes through the coil, a magnetic field is generated, and the Hall sensor has a signal. Output.
Closed-loop current sensor

The magnetic balance current sensor is also called Hall closed-loop current sensor, also known as compensation sensor, that is, the magnetic field generated by the measured current Ip of the main loop at the magnetic flux ring passes through a secondary coil, and the magnetic field generated by the current is compensated, so that The Hall device is in the working state for detecting zero magnetic flux.
The specific working process of the magnetic balance current sensor is: when a current passes through the main loop, the magnetic field generated on the wire is collected by the magnetic ring and induced on the Hall device, and the generated signal output is used to drive the corresponding power tube and Turn it on to obtain a compensation current Is. This current then generates a magnetic field through the multi-turn winding, which is exactly the opposite of 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 and the number of turns is equal, Is no longer increases, and the Hall device at this time plays the role of indicating zero magnetic flux, which can be balanced by Is at this time. Any change in the measured current will disrupt this balance. Once the magnetic field is out of balance, the Hall device has a signal output. Immediately after power amplification, a corresponding current flows through the secondary winding to compensate for the unbalanced magnetic field. The time required from magnetic field imbalance to re-equilibrium is less than 1μs in theory. This is a dynamic balancing process.

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