The instruments with moving-coil movement and built-in rectifier are intended for panel mounting in power and low-current installations where measurements of alternating currents and voltages with a small intrinsic consumption of the measuring instrument are required. They measure the arithmetic mean value of the alternating current or voltage in a frequency range from 40 to 5000 Hz. The scale is displayed in r.m.s. values with sinusoidal form of the measured variable. Distortion of the sine curve causes measurement errors.
Germanium diodes with very low reverse current are used for rectification. The scales of the instrument are almost linear, except for voltmeters below 10V, where they are somewhat compressed in the initial part. For ammeters, a current transformer is built in for measurements with transducers .../1A and.../5A. The design of the housing makes it possible to change the scale more quickly, which means that different scale designs for measuring electrical and non-electrical quantities are possible with the measuring range remaining unchanged. If, for example, the primary value of an instrument connected via measuring transformers (ranges 1A, 5A, 100V) is changed, it is not necessary to install a new instrument, only the scale is replaced.