Accurately measuring current draw

[Eoin_Mcguinn at Dell.com]

My understanding is that with clamp-meters, you have to have access to the live feed, physically separated from the neutral. 
If you have this, go ahead and try with a meter, but you are going to loose the Power Factor calculation which an in-line meter can provide.

The rule of thumb with supplies is that the loading should be designed around 75% of the available load. For example, 6 amps of an 8 amp supply.

Anyhow, my preference would be to obtain a power logger with a serial port output which will enable you to measure the consumption over a reasonable range.

-----Original Message-----
From: linux-poweredge-bounces at dell.com [mailto:linux-poweredge-bounces at dell.com] On Behalf Of Faris Raouf
Sent: 05 March 2008 13:30
To: linux-poweredge-Lists
Subject: Accurately measuring current draw

Following on from the discussions on the Kill-A-Watt in another thread, has anyone used a proper clamp meter for measuring current?

I'm thinking about buying a cheap-ish one ($80/£40), along with a plug-in device similar to the Kill-A-Watt in order to compare these two options (which I consider "slightly-pro" and "consumer" - the clamp meter is only slightly-pro because it isn't an expensive one - no calibration certificate etc.

But I'd appreciate any feedback on how accurate the Kill-A-Watt type products might be before I bother doing so.

What I mean by accurate in this sense is given, say, an 8A power feed in a data centre, I want to be 100% sure that if my test figures say each server takes less than 1A under extreme load and I have no more than 8 of them I'm not going to trip the breaker.

If there's more to this than meets the eye (e.g. all that RMS stuff and god knows what else that I've forgotten about since I did my Physics) please can someone pipe up and let me know?


Faris.





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