Power Meters

Power meters are used for high accuracy measurement from both DC and AC circuits. Measurements can be obtained for single phase and three phase AC systems. Some power meters can measure true RMS power. Power meters can be used for the measurement of power in various conditions including half-wave and full-wave rectified waveforms, mixed AC/DC waveforms, and distorted waveforms.

One very important specification is the range of power is to be measured. Also important for selecting one of these meters is how many channels it is to have and what the sampling rate should be. The type of power measured is critical as well. Four different types of measurement are possible: active power, apparent power, reactive power and power factor. Active power is the time rate of transferring or transforming energy. The electrical power at a single terminal pair is the product of the voltage and the current. Apparent power is the product of the RMS values of voltage and current. Reactive power is the product of the RMS value of the voltage and the RMS value of the quadrature component of the current. Finally, power factor is the ratio of active power to apparent power. Power factor is sometimes called quality factor.

A large number of features are available for power meters. External shunts can be used to extend the current input range. Integrating Functions allow the active power and current to be integrated (Wh and Ah). Scaling functions allow the potential transformer and current transformer ratio to be preset. The meters can support a wide range of current sensors used for evaluating inverter driven equipment and high frequency lighting equipment. Automatic range switching means that when the measured value falls out of the rated range the meters can automatically switch to the appropriate unit for the range that is being measured. Harmonic analysis is phase measurement between 3-phase inputs and measurement of active, reactive or apparent power of the fundamental wave. Other more general features for power meters can include filtering, data logging, event triggering, and application software for use with a computer.

Power Meters Directory at The Electricity Forum contains a listing of power meters, electric meter manufacturers and suppliers, Fluke meters, watthour, hour, volt, voltage, power factor, subcategories: