Many devices operating in electrical circuits require accurate measurements in real time. Much depends on the accuracy of these measurements: the quality of regulation processes in control circuits, reliable operation of protection, calculation when calculating power consumption in electrical installations, etc. Usually, for such measurements, special devices are used, which 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 a particular circuit design. Only the principle of its operation remains unchanged - in accordance with the coefficient embedded in it, it converts a signal from a measuring transformer or other device into a voltage signal that is consistent with the rest of the circuit.
Distinguish between a current sensor that is designed to work in AC and, accordingly, DC voltage circuits. As an example, consider the work of each of them. For AC voltage asThe measuring element usually uses a current transformer. This 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 changing parameter. The above transformer will not work in such a circuit, since at its output we can only get the dynamics of the measured parameter. Usually in such schemes a special shunt is used, with
increased resistance relative to the rest of the electrical circuit. It is mounted directly in line. In this case, the voltage drop in this section is removed, which will be given to the DC sensor. Since the input circuits in such a circuit are at a high potential, such a sensor performs several functions at once. It galvanically separates the power and measuring circuits and simultaneously scales the received signal.
A typical circuit, according to which such a current sensor operates, consists of a high-frequency pulse generator, an isolating key and a transformer. The incoming measuring signal is converted using a generator and a separating key, usually assembled on a field-effect transistor. The alternating voltage thus converted is transferred to an isolating transformer. After that, it is filtered and amplified depending on the coefficient laid downwhen designing.
A slightly different principle of operation is incorporated in the so-called Hall current sensor. It measures the strength of the magnetic field that 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 he is universal and able to function normally in any circuits. These sensors are compact and have good performance.
