Model MA & MV series are designed for general performance to accept AC input signals & convert AC to DC of average responding to scale rms reading. Model MAR & MVR series, a true-root-mean-square conversion unit, are able to measure a distorted sinusoidal with harmonics or periodical of non-sinusoidal signal. The unit type of ration input ranges are defined to accept a secondary signals from PT or CT & calibrated to a primary reading & the named type of input ranges just directly follow inputs as a display reading. The designed specifications of the units, truly a real power system design, compliant ANSI-IEEE & IEC, VDE standards with full protection for surge intrusion & accident over input assuring reliable operation.