Wattmeter - definition
Wattmeter - definition
Wattmeter is a measuring instrument used for the direct measurement of active power in electrical circuits direct current (DC) or alternating current (AC). Its purpose is to determine the amount of energy transferred by a source to a load per unit time, expressed in watts (W). In alternating current (AC) systems , this measurement takes into account both the voltage and current values and the phase shift between them, which distinguishes it from apparent or reactive power meters.
The classic analogue wattmeter is based on an electrodynamic or electromechanical operating principle, where the torque produced by two coils systems - current and voltage - is proportional to the instantaneous value of the active power. The result is presented by a pointer on a scale and the accuracy of the measurement depends on the quality of the components used, the internal resistance and the frequency of the supply voltage. Modern digital wattmeters use analogue-to-digital converters and microprocessor systems to analyse the signal samples, allowing real-time results with high precision and additional calculation functions.
In AC measurement, wattmeters enable power evaluation in single-phase and three-phase systems, in both symmetrical and asymmetrical connections. In more advanced applications, multi-channel wattmeters are used to enable simultaneous monitoring of multiple power lines and load distribution analysis. Practical applications include energy consumption control, equipment efficiency analysis, plant diagnostics and energy billing.
The accuracy of a wattmeter depends on the class of instrument, the measuring range, the type of signal to be processed and the environmental conditions. In laboratory and industrial measurements, wattmeters with a data logging function are also used, enabling long-term monitoring of power parameters within energy management systems.
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