Category ratings on test gear (maximum voltage)

[Guineafowl]

Hi all. What does the voltage rating in each category I/II/III/IV actually mean? For example, my multimeter is Cat III rated to 300V. Is this RMS? Peak? Peak-peak?

Our supply here is 230V RMS AC, but this means the momentary peak is about + and - 330V (relative to neutral/ground) and the peak-peak is of course 660V.

Can I therefore use it to measure mains voltage at a socket? My interpretation is:

1. If RMS, yes.
2. If peak, no.
3. If peak-peak, definitely no.

 

[Nidum]

http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

 

[Guineafowl]

http://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

As far as I can see the voltage rating is DC or AC RMS to ground, i.e. 230V, and implies a higher transient level, so I should be fine. That said, it is only a UNI-T meter so maybe I should take the rating with a pinch of salt...