Many devices operating in electrical circuits require accurate measurements in real time. Much depends on the accuracy of these measurements: the quality of regulatory processes in control circuits, reliable operation of protection, costing when calculating power consumption in electrical installations, etc. Typically, for such measurements use special instruments that are part of the main circuit. For example, a 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 laid down 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.
A current sensor is distinguished, which is designed to work in AC and, accordingly, DC voltage circuits. As an example, we can consider the work of each of them. For ac voltage, a
current transformer is usually used as a measuring element
. This is a non-contact device that monitors the state of a controlled power circuit. The signal from it enters the current sensor, the purpose of which is to scale the received signal with a control circuit.
The situation is somewhat different if we are dealing with a constant or slowly changing parameter over time. The above transformer will not work in such a circuit, since at its output we can only get the dynamics of the measured parameter. Typically, such circuits use a special shunt, with
increased resistance 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 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 works, consists of
a high-frequency
pulse generator , an isolation key and a transformer. The incoming measuring signal is converted using a generator and a dividing key, usually assembled on a field effect transistor. The alternating voltage converted in this way is transferred to an
isolation transformer. After that, it is filtered and amplified depending on the coefficient incorporated in the design.
A slightly different principle of operation is laid in the so-called Hall current sensor. It measures the intensity of the magnetic field, which occurs due to the flow of current in the conductor, and converts it into an output voltage signal. A feature of his work is that it is universal and able to function normally in any circuit. Such sensors are compact and have good performance.