Amperes to Arms current draw conversion confusion.

September 6, 2011 9:02 AM

In measurements of electrical current draw, how do "amperes" compare to "Arms"?

I'm spec'ing mains power to an amplifier right now and its spec sheet reads:

Peak inrush current draw: 5 A

but then for operation current draw at switches to the measurement unit of "Arms", eg -

Quiescent Power (no load): 2.8 Arms
1/3 of full power (-5dB): 18 Arms

My google-fu is failing me and I can't seem to figure out any calculations relating "amps" and "arms" together.

If you want the specific example, here's the link to the PDF:

http://labgruppen.com/media/downloads/product/fP2400Q_ETL_spec.pdf

posted by aloiv2 to Technology (4 answers total)

Best answer: I think it's Amps _{root-mean-square}, or A_rms.

This is a way of measuring average amps over a period of time. See for example, wiki.
posted by flug at 9:09 AM on September 6, 2011

Flug has it.
posted by Brockles at 9:22 AM on September 6, 2011

flug has it, and although IANAEE I think you can just treat the rms value as the current draw of the device and be fine (that's why they give you the rms value).

I'm sure a friendly mefite will correct me if I'm wrong!
posted by samj at 9:23 AM on September 6, 2011

Response by poster: *facepalm*
seeing it with the subscript makes so much more sense.

Thanks all.
posted by aloiv2 at 9:24 AM on September 6, 2011