Monitoring of KWH power consumption

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Ken Schumm

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Dec 1, 2000, 3:00:00 AM12/1/00
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I want to monitor the KW power consumption of about a dozen
devices in our house. Ideally, I'd like to acquire data in a
centralized and coordinated fashion, plotted against temperature
and humidity.

I can build a system to do this out of a PC, data acquisition
card, and current/voltage/temperature/RH sensors, but I was
hoping there was an off the shelf system somewhere that might
do this. My time is tight, and if I have to roll-my-own it
may not get done for a year or more.

Does anyone know of available products that might accomplish
this functionality? The perfect product would consist of
sensor modules that plug into an ethernet network and can be
polled with tcp/ip, but hardwiring devices to a central
monitoring point would be acceptable.

TIA


Ken Schumm

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Dec 1, 2000, 3:00:00 AM12/1/00
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Previously, Dave Houston wrote in comp.home.automation:
> I don't think you'll find anything off the shelf (except very expensive
> 3-phase industrial instruments) and I think you'll have to settle for RS-232
> but here is the best thing available for power measurement. It does it right
> (measuring voltage and current is not the right way) and it's reasonably
> priced (at least for a single channel).
>
> http://www.brandelectronics.com/powermeter.htm
>
> You'll probably have to roll your own temperature and humidity recorder but
> it would be fairly easy to do those. The quick way would be an Ocelot and a
> couple of Bobcats.

Thanks for the pointer.

I know you can't get KW from E and I, but I should be able to compute
the power factor. Once I've got that I'd think it would be be pretty
darn accurate.

I'd still rather use off the shelf stuff, though. I've got enough
programming to do in my day job, which usually ends up being a night
job too :(

[...]


Dave Houston

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Dec 1, 2000, 8:58:57 PM12/1/00
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I don't think you'll find anything off the shelf (except very expensive
3-phase industrial instruments) and I think you'll have to settle for RS-232
but here is the best thing available for power measurement. It does it right
(measuring voltage and current is not the right way) and it's reasonably
priced (at least for a single channel).

http://www.brandelectronics.com/powermeter.htm

You'll probably have to roll your own temperature and humidity recorder but
it would be fairly easy to do those. The quick way would be an Ocelot and a
couple of Bobcats.

Robert Surtees

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Dec 1, 2000, 9:22:27 PM12/1/00
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Take a look at the Cutler-Hammer page. Power Manager / Power Sensor might be
what you have in mind.

http://www.ch.cutler-hammer.com/apc/products.html

I have had no experience with this product nor do I know anything about the
pricing.

"Ken Schumm" <kwsc...@qsolv.com> wrote in message
news:Voyager.001201151834.4873A@dilbert...

Dave Houston

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Dec 1, 2000, 11:25:38 PM12/1/00
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After posting the response below, I learned that Brand now has a
multi-channel (1-32) meter that can also handle temp & humidity. So there is
an off-the-shelf solution. But it is still only RS-232. The direct link
is...

http://www.brandelectronics.com/One.htm

dhou...@fuse.net (Dave Houston) wrote:


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Dave Houston

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Dec 2, 2000, 3:00:00 AM12/2/00
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Ken Schumm <kwsc...@qsolv.com> wrote:

>Previously, Dave Houston wrote in comp.home.automation:

>> I don't think you'll find anything off the shelf (except very expensive
>> 3-phase industrial instruments) and I think you'll have to settle for RS-232
>> but here is the best thing available for power measurement. It does it right
>> (measuring voltage and current is not the right way) and it's reasonably
>> priced (at least for a single channel).
>>
>> http://www.brandelectronics.com/powermeter.htm
>>
>> You'll probably have to roll your own temperature and humidity recorder but
>> it would be fairly easy to do those. The quick way would be an Ocelot and a
>> couple of Bobcats.
>

>Thanks for the pointer.
>
>I know you can't get KW from E and I, but I should be able to compute
>the power factor. Once I've got that I'd think it would be be pretty
>darn accurate.
>
>I'd still rather use off the shelf stuff, though. I've got enough
>programming to do in my day job, which usually ends up being a night
>job too :(

I don't think power factor is always simple to compute but it really depends
on the specific loads. Here's a URL that discusses why PF isn't always
simple...

http://www.microconsultants.com/tips/pwrfact/pfarticl.htm

If you do opt for Brand's unit, it might be of interest to compare its
readings with your calculations.

Randy Peeples

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Dec 2, 2000, 3:00:00 AM12/2/00
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Hi..

You'll find that the "Power Factor" is very nearly 1.00. There are very few
loads that are highly inductive or capacitative in a home.. Therefore..
simply multiply your voltage (which is also very stable over any one month
period) by the current drawn.. That means if you know the current, you know
the kilowatts being used. You may have to monitor the voltage to prove this
to yourself. The only time when there may be a voltage fluctuation of a few
volts is in the heat of summer based on my observations unless you live in
the "sticks".. maybe "FLORI-DUH"..

It's called engineering.. educated guesses based on 1. experience, and 2.
mathematical modeling.

Hope this helps..
Randy

"Ken Schumm" <kwsc...@qsolv.com> wrote in message
news:Voyager.001201151834.4873A@dilbert...

> I want to monitor the KW power consumption of about a dozen
> devices in our house. Ideally, I'd like to acquire data in a
> centralized and coordinated fashion, plotted against temperature
> and humidity.
>
> I can build a system to do this out of a PC, data acquisition
> card, and current/voltage/temperature/RH sensors, but I was
> hoping there was an off the shelf system somewhere that might
> do this. My time is tight, and if I have to roll-my-own it
> may not get done for a year or more.
>
> Does anyone know of available products that might accomplish
> this functionality? The perfect product would consist of
> sensor modules that plug into an ethernet network and can be
> polled with tcp/ip, but hardwiring devices to a central
> monitoring point would be acceptable.
>
> TIA
>
>
>


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Edward Cheung

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Jan 14, 2001, 7:01:46 AM1/14/01
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Ken Schumm wrote:
>
> I want to monitor the KW power consumption of about a dozen
> devices in our house.

For a home-brewn solution, refer to:
http://cheung.webhop.net/automa/power.htm

+-------------------------------------------+
| Edward Cheung, Ph.D. |
| NASA Goddard Space Flight Center |
| J&T/Code 442 |
| Greenbelt, MD 20771 |
| 301-286-8027(office) 286-1659(fax) |
| http://cheung.place.cc |
| edward.b...@gsfc.nasa.gov |
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