Moving iron meters are suitable for the measurement of true rms a.c. current or voltage. All moving iron meters have interchangeable scaleplates. Scales are non-linear and are calibrated down to 20% of full scale. Ammeters are available with a 2x overload as standard or a 6x overload for monitoring motor start up currents. Voltmeters are also available with scales for high voltage measurement via voltage transformers. All moving iron meters are calibrated for operation at 50/60Hz but calibration at 400Hz is available upon request. Moving iron meters may be used to measure d.c. at reduced accuracy.