Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Can one buy kwh meters relatively cheaply? I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.

--
Chris Green

wrote in message ...
Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Can one buy kwh meters relatively cheaply? I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.

Surely you already have one in the meter locker?

wrote:
Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Can one buy kwh meters relatively cheaply? I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.


http://www.tlc-direct.co.uk/Products/RDCRED60.html

On Thu, 03 Jun 2010 13:27:51 +0100, wrote:
On 3 Jun,
wrote:

Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

What spec is that? my atom board one with one hard drive takes about 40
watts. I wouldn't expect much less other than for a netbook.


A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

The Aldi/lidl ones I have seem quite accurate, but at low (10w) levels the
resolution is poor.

You could always increase the power consumption to get it into the meter's
linear range. For example, get some 60W bulbs (3 or 4) in parallel. Connect
them up to the meter and measure the power consumption. Plug in the load from
your low power device as well as the bulbs and see how much _extra_
consumption is taken.


I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Can one buy kwh meters relatively cheaply? I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.

I compared my cheap ones with one and found them accurate. You should be
able to pick a proper mechanical KWH meter for less than £20.

wrote in message ...
Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

http://www.maplin.co.uk/Search.aspx?...eter&source=15


I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

I'm not sure how it calculates things but current and voltage are usually
out of phase with computer power supplies so there's a few different reading
that can be taken.
The power in watts or kwh (over time) then there's the VA which is amps
X volts which gives you power but this might not be the same as watts.

I just tried one of our small Dell PCs in the lab, when it's off but plugged
in it's 10 watts and 125Watts when on, excluding monitor.

I find it hard to believe that a PC is 25-30w when on.
My 24" iMac is about 110w changing the LCD screen from minium to
maxium xhanged the power usage by nearly 20 watts.
Doenloadign a file added 5watts as I guess ther HD was being accessed.



Can one buy kwh meters relatively cheaply? I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.

--
Chris Green

In article ,
writes:
Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

I found the Brennendal one to be very inaccurate. It was suggested
to me that this happens if you don't fit batteries in it, but I
never got around to seeing if that was the case.

I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Simply buy a different make. AFAIK, it's only the Brennendal which
is very inaccurate. Get one which can give you the power, VA, and
power-factor readings - it's likely to understand the concept of
non-sinusoidal current loads.

I also still have one I made about 30 years ago, before the cheap
plug-in ones appeared.

BTW, some time ago, I wrote a blog on the significance of power-factor,
which you might find interesting, with some java applets you can play
with changing various parameters and see what the effect is...
http://blogs.sun.com/agabriel/

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Thu, 03 Jun 2010 13:27:51 +0100, me9 wrote:

Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

What spec is that? my atom board one with one hard drive takes about 40
watts. I wouldn't expect much less other than for a netbook.

Try a fanless VIA EPIA board, lower end, running off a CF card.

More like 15-20W.
--
Use the BIG mirror service in the UK:
http://www.mirrorservice.org

*lightning protection* - a w_tom conductor

On 3 June, 12:27, wrote:
Is there any cheap/easy way to measure the power consumption of mains
powered equipment that consumes a few tens of watts and is almst
certainly non-sinusoidal? *In particular I want to measure the power
consumption of a (hopefully) low power PC that should be consuming
around 25 watts.

A cheap plug-in power meter (a Brennendal one) claims it's consuming
about 50 watts but I'm not at all convinced it's telling me the truth.

I know 'proper' power meters are expensive and I don't really want to
spend lots of money, nor do I really want a very accurate answer. *If
I can just confirm it's consuming something between 20 and 30 watts
I'll be happy.

Can one buy kwh meters relatively cheaply? *I'm quite happy to wire
one up to a plug and socket and use that over several hours to see
what's being consumed.

--
Chris Green

Reconditioned kWh meters are available on ebay for around a tenner