An instrument, which depends upon the magnetic reaction between a fixed, and a moving coil producing deflection of a pointer over a graduated scale. This type of movement responds to root-mean-square (RMS) or affective current. The ability to truly measure distorted waves having high peaks is far superior to other devices. Since by convention, scales are calibrated in RMS quantities, the electrodynamometer instrument can be used with equal accuracy on DC or AC. Watt, volt, amp, VAR and power factor meters use this construction. Frequency coverage can extend from DC to 2500 Hz with a cap from DC to 15Hz due to excessive pointer vibration.