virtamittaukseen

Virtamittaukseen, or current measurement, is the process of determining the magnitude of electrical current flowing in a conductor or circuit. In engineering practice, it is essential for monitoring, control, protection, and characterization of electrical systems. The measurement can be performed on alternating current (AC) or direct current (DC), and the chosen method depends on current level, frequency, isolation requirements, and acceptable burden on the circuit.

Common methods include insertion-type ammeters (placed in series with the circuit), shunt resistors (low-value resistors that convert current to a small voltage), Hall-effect sensors (which measure magnetic field produced by current and can be isolated), current transformers (for high currents in AC circuits), and Rogowski coils (AC measurement with flexible coil). For non-contact needs, clamp meters use current transformers clamped around a conductor. For very high currents or power systems, instrument transformers and differential measurement are used.

Accuracy depends on sensor type, burden, temperature, frequency, and calibration. DC current measurement with Hall or shunt is common; AC measurement must consider phase error and waveform distortion. Isolation and safety are important, and proper calibration ensures traceability to standards.

Applications encompass power distribution, motor control, automotive electronics, renewable energy, laboratory testing, and metrology. In instrumentation, the choice of sensor balances invasiveness, bandwidth, and measurement range, as well as the required isolation and environmental conditions.

Standards govern the design and performance of current transformers and related instrumentation. Relevant standards include IEC 61869 for instrument transformers and IEC 60044 for current transformers, along with general measurement safety and calibration requirements.