Er, Fluke ain’t makin’ this stuff up. It’s evolved from UL Standard 61010B-1. The various “CAT” ratings are installation/overvoltage categories with Category III and IV having the highest overvoltage withstand.
One way to look at it... The higher the circuit voltage and short-circuit capability where the meter is applied, the higher the needed CAT rating. {It's nice if the meter in your hand does not vent flames or detonate in the process of checking voltage in a live panelboard.}
[This message has been edited by Bjarney (edited 10-01-2003).]
