For industrial or commercial applications, the Round style panel meter offers maximum reliability and ±2% full scale (F.S.) accuracy for iron-vane movements, and ±3% for rectifier types. With a black phenolic case and glass window for optimum viewing, the Round style meter is a popular selection for industrial applications because the cover extends to the back of the case. AC units have either iron-vane type or rectifier type movements and are calibrated at 60Hz. Ironvane type current meters have a frequency range of 25 to 800Hz (for ±1% deviation from value at 60Hz). All rectifier types have a 25Hz to 10KHz range. Two different standard sizes of 2-1/2" and 3-1/2" are available to measure various current ranges. This style meter is ideal for many other electrical functions.