Current sensor: principle of operation and scope

Many devices operating in electrical circuits require accurate measurements in real time. A lot depends on the accuracy of these measurements: the quality of the control processes in the control circuits, the reliable operation of the protection, the calculation when calculating the 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 many devices. It can be implemented on a variety of elements, depending on a particular circuit design. Only the principle of its operation remains unchanged-in accordance with the coefficient incorporated in it, it converts the signal from the measuring transformer or other device into a voltage signal that is consistent with the rest of the circuit.

There is a current sensor, which is designed to work in circuits of alternating and, consequently, constant voltage. As an example, you can consider the work of each of them. For AC voltage, a current transformer is usually used as a measuring element . It is a non-contact device that monitors the state of the controlled power circuit. The signal from it goes to 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 dealing with a constant or slowly varying parameter in time. The above-described transformer will not work in such a scheme, since at its output we can obtain only the dynamics of the measured parameter. Usually such schemes use a special shunt, with Increased in relation to the rest of the electrical circuit by resistance. It is mounted directly into the line. In this case, the voltage drop in this section is removed, which will be transmitted to the DC sensor . Since the input circuits in such a circuit are at 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, which operates such a current sensor, consists of a high-frequency pulse generator , a separation switch and a transformer. The incoming measuring signal is converted using a generator and a separation switch, usually assembled on a field effect transistor. The AC voltage converted in this way is transferred to the isolation transformer. After that, it is filtered and amplified, depending on the factor incorporated in the design.

A slightly different principle of operation is incorporated in the so-called Hall current sensor. It measures the intensity of the magnetic field, which arises because of the current flowing through the conductor, and converts it into an output signal by voltage. The peculiarity of his work is that it is universal and is able to function normally in any circuits. Such sensors are compact and have good performance characteristics.