ANSI C39.1

Description / Abstract: This standard applies to the following kinds of electrical indicating instruments for direct and alternating current, including instruments with prefixes such as micro-, kilo-, etc:

(1) Ammeters

(2) Voltmeters

(3) Wattmeters

(4) Varmeters (reactive-volt-ampere meters)

(5) Frequency meters

(6) Power-factor meters

(7) Synchroscopes

(8) Indicating instruments of the aforementioned kinds, but indicating derived quantities

(9) Indicating instruments of the aforementioned kinds with self-contained electronic devices when the supply is obtained from the measured quantity

This standard may apply, with suitable exceptions, to instruments constructed for special requirements - for example, ultrasensitive dc microammeters, high-resistance voltmeters, thermomilliammeters, thermovoltmeters of the vacuum-couple type, and instruments with special and unusual ranges.

This standard does not apply to the following kinds of instruments with special and unusual ranges.

This standard does not apply to the following kinds of instruments:

(1) Indicating instruments provided with arrangements for curve drawing, contact making, etc

(2) Small instruments of types and sizes where the indications are only approximate - for example, small polarized-vane ammeters used on automobiles, battery-charging outfits, etc

(3) Instruments that contain active devices such as transistors, electron tubes, etc, unless the supply for these active devices is obtained from the measured quantity

(4) Indicating instruments for the measurement of resistance, conductance, or impedance

(5) Multifunction instruments or clamp-on ammeters