Virtamittaus

Virtamittaus is the process of determining the electric current flowing through an electrical conductor or circuit. It applies to alternating current (AC) and direct current (DC) and is essential in power engineering, electronics, and laboratory measurements. The basic unit of current is the ampere (A).

Measurement can be done by inserting a measuring element in series with the circuit or by using non-contact methods. The most common method in low‑power circuits is a shunt resistor in series, with the voltage drop proportional to the current read by a voltmeter or dedicated ammeter. For safety and isolation, clamp‑on meters measure the magnetic field around a conductor and do not require breaking the circuit. Hall effect sensors provide contactless measurements and can handle DC and AC signals; Rogowski coils are used for very high currents and fast transients.

Accuracy and waveform considerations are important. True RMS meters measure the effective value of non‑sinusoidal waveforms, while many meters provide average‑responding readings that require correction for non‑sinusoidal sources. Measurement error depends on burden voltage, frequency, temperature, and conductor configuration. Calibration and traceability to standards are important for precision work; accuracy classes and specifications vary by instrument and application.

Applications include monitoring power consumption and electrical safety in buildings, testing and development of power electronics, automotive electrical systems, and laboratory experiments. In all cases, proper setup and understanding of the chosen method are essential to obtain reliable results and to avoid disturbing the circuit under test.

Safety and standards are important in virtamittaus. Measurements often require circuit isolation, appropriate equipment rating, and adherence to applicable safety standards and national regulations to protect personnel and equipment.