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Category ratings on test gear (maximum voltage)

  1. Sep 8, 2016 #1
    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.
  2. jcsd
  3. Sep 8, 2016 #2


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  4. Sep 8, 2016 #3
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