Current sensor: principle of operation and scope

Many devices operating in electricalcircuits require accurate measurements in real time. Much depends on the accuracy of these measurements: the quality of control processes in control circuits, reliable protection operation, calculation when calculating power consumption in electrical installations, etc. Usually for such measurements use special devices that are part of the main circuit. For example, the current sensor is widely used in the operation of many devices. It can be implemented on a variety of elements, depending on one or another circuit design. It remains unchanged only the principle of its operation - in accordance with the factor incorporated in it, it converts the signal from a measuring transformer or other device into a voltage signal that is consistent with the rest of the circuit.

There is a current sensor that is designed forwork in the circuits of alternating and, accordingly, constant voltage. As an example, consider the work of each of them. For alternating voltage, a current transformer is usually used as a measuring element. This is a contactless device that monitors the state of the controlled power circuit. The signal from it enters the current sensor, the purpose of which is to scale the received signal with the control circuit.

The situation is somewhat different if we are dealingwith a constant or time-varying parameter. The above-described transformer in this scheme will not work, since at its output we will be able to get only the dynamics of the measured parameter. Usually in such schemes a special shunt is used, with

elevated relative to the restelectrical circuit resistance. It is mounted directly to the line. In this case, the voltage drop is removed in this area, which will be given to the DC sensor. Since the input circuits in such a circuit are under high potential, such a sensor performs several functions at once. It galvanically separates the power and measuring circuits and simultaneously scales the received signal.

Typical scheme by which such a sensor workscurrent, consists of a high-frequency pulse generator, a dividing key and a transformer. The incoming measurement signal is converted using a generator and a dividing switch, usually assembled on a field-effect transistor. The alternating voltage converted in this way is transferred to the isolation transformer. After that, it is filtered and enhanced depending on the coefficient incorporated in the design.

A slightly different principle of operation is laid down in socalled Hall current sensor. It measures the magnetic field, which occurs due to the flow of current in the conductor, and converts it into a voltage output signal. A feature of his work is that it is universal and able to function normally in all circuits. Such sensors are compact and have good performance.