Power meters are used for high-accuracy measurements of power over a wide-frequency bandwidth, and from both AC and DC circuits. Measurements can be obtained for single-phase and three-phase AC systems. Some power meters can measure true RMS power. Root mean square (RMS) is the value obtained when the maximum voltage or current is divided by the square root of two. 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.