Because of its special form, the FN 0103 moving-iron instrument is convenient for building into different control devices. The accuracy class is 1.5. The scale is not interchangeable.
It operates in a range from 15 Hz to 100 Hz and measure true RMS values independently on the signal form of voltage. A non-linear graduation at the beginning of the scale allows reading from approximately 15 % of measuring range onwards. Its front frame is 86x72 mm and has 65 mm diameter cutting for mounting.