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 Post subject: Power Meters: Real Power vs. Apparent Power
PostPosted: Tue Jun 12, 2007 3:43 pm 
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Joined: Tue Jun 12, 2007 3:19 pm
Posts: 134
Location: UK
Hi, I bought this Power Meter from Maplins to measure my power consumption:

Image

However, I have a problem with the readings it is giving me for volt-amps and watts. If I understand this right, the watts, as a measure of real power, should equal the volt-amps being drawn if the power factor is 1. As my PSU is rated an Active PFC of 0.99, the reading from watts and volt-amps should be roughly equivalent, correct?

But the two are wildly different on it. Volt-amps measures 167 and watts a mere 21, and the device give me a power factor of 0.11. I got a similar PF from an ordinary 60W bulb. Is this device nackered, or am I missing something?

Thanks for your help!


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PostPosted: Tue Jun 12, 2007 5:50 pm 
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Joined: Tue Jan 04, 2005 4:02 pm
Posts: 1608
Location: United States
I believe you are correct in your assumption that the meter is defective. Try returning it for another and see how the replacement does. :)

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 Post subject:
PostPosted: Tue Jun 12, 2007 6:08 pm 
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Joined: Wed Jun 04, 2003 11:20 am
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Location: california
An incandescent light bulb is a purely resistive load which has a power factor of 1. Fluorescent bulbs are a different story. If your meter is reading anything other than va = watts for a pf of 1 on an incandescent bulb, then it is defective.

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 Post subject:
PostPosted: Tue Jun 12, 2007 7:15 pm 
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Joined: Tue Jun 12, 2007 3:19 pm
Posts: 134
Location: UK
fractal wrote:
An incandescent light bulb is a purely resistive load which has a power factor of 1. Fluorescent bulbs are a different story. If your meter is reading anything other than va = watts for a pf of 1 on an incandescent bulb, then it is defective.

It was only giving me 8W for a 60W incandescent bulb, which is one way to save power I guess. Looks as if an RMA is in order.


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 Post subject:
PostPosted: Fri Jun 22, 2007 7:41 pm 
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Joined: Tue Jun 12, 2007 3:19 pm
Posts: 134
Location: UK
Got a replacement for this model today entombed in a sarcophagus of bubblewrap, and it appears to be working correctly now. I would suspect that this item qualifies as "fragile" and should be treated gently!


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