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Bob Eager
 
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Default Measuring power consumption

There was some discussion a while ago about a Maplin gadget that did a
fair job (I think) of measuring appliance power consumption.

I hate dealing with Maplin, and the discussion didn't cover a lot else
at the time.

So...are there any other, not too expensive, measuring gadgets that will
at least give a rough idea? I looked through the CPC catalogue but
didn't find anything (not that that means a lot).
--
Bob Eager
begin a new life...take up Extreme Ironing!
  #2   Report Post  
Dave Liquorice
 
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On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?


Try http://www.machinemart.co.uk/product.asp?p=010916213

--
Cheers
Dave. pam is missing e-mail



  #3   Report Post  
Bob Eager
 
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On Sun, 22 May 2005 00:24:36 UTC, "Dave Liquorice"
wrote:

On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?


Try http://www.machinemart.co.uk/product.asp?p=010916213


Thanks...that looks useful.

I found the SAME item (listed there at about 15 quid plus VAT, total of
about 24 quid including shipping) for 39.95 plus 10.00 shipping plus VAT
(i.e. 57 quid) somewhere else!


--
Bob Eager
begin a new life...take up Extreme Ironing!
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Set Square
 
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Default

In an earlier contribution to this discussion,
Dave Liquorice wrote:

On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?


Try http://www.machinemart.co.uk/product.asp?p=010916213


Yes, I've got one of those - and it gives believable figures - at least for
resistive loads like light bulbs.

I got mine from Machinemart about 18 months ago - when I think it was
slightly dearer than the current price.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #5   Report Post  
Ian_m
 
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Default

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Dave Liquorice wrote:

On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?


Try http://www.machinemart.co.uk/product.asp?p=010916213


Yes, I've got one of those - and it gives believable figures - at least
for
resistive loads like light bulbs.

I got mine from Machinemart about 18 months ago - when I think it was
slightly dearer than the current price.
--
Cheers,
Set Square
______

My power/consumption meter cost £6.99 from Lidls a year or two ago. Works
fine, enter your electicity cost per unit and it tells you the total cost in
£ and p. Currently on fish tank to see the running costs. One complication
is it tells you the power factor of the load, but not how, if it does at
all, affect the reading, because obviously there are two powers now when
power factor is not one, but instructions don't tell you which. I suspect
you have to multiply the meter read power by power factor to work out your
power in a domestic environment, but I may be wrong.




  #6   Report Post  
Pete C
 
Posts: n/a
Default

On 21 May 2005 23:15:21 GMT, "Bob Eager" wrote:

There was some discussion a while ago about a Maplin gadget that did a
fair job (I think) of measuring appliance power consumption.

I hate dealing with Maplin, and the discussion didn't cover a lot else
at the time.

So...are there any other, not too expensive, measuring gadgets that will
at least give a rough idea? I looked through the CPC catalogue but
didn't find anything (not that that means a lot).


Hi,

How about a recon electric meter, something like:

http://www.toolstation.com/messages.html?code=22833&mainWin=1

or maybe available from a boot sale or similar.

Do you still have 12 PCs?

cheers,
Pete.
  #7   Report Post  
Ian Stirling
 
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Default

Ian_m wrote:
"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Dave Liquorice wrote:

On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?

Try http://www.machinemart.co.uk/product.asp?p=010916213


Yes, I've got one of those - and it gives believable figures - at least
for
resistive loads like light bulbs.

I got mine from Machinemart about 18 months ago - when I think it was
slightly dearer than the current price.
--
Cheers,
Set Square
______

My power/consumption meter cost ?6.99 from Lidls a year or two ago. Works
fine, enter your electicity cost per unit and it tells you the total cost in
? and p. Currently on fish tank to see the running costs. One complication
is it tells you the power factor of the load, but not how, if it does at
all, affect the reading, because obviously there are two powers now when
power factor is not one, but instructions don't tell you which. I suspect
you have to multiply the meter read power by power factor to work out your
power in a domestic environment, but I may be wrong.


You are.
In an industrial environment, it's important, as the power company may charge
you extra.
But in a domestic one, (at least in the UK, and I believe everywhere else)
it's not a factor.
  #8   Report Post  
Ian Stirling
 
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Default

Bob Eager wrote:
On Sun, 22 May 2005 00:24:36 UTC, "Dave Liquorice"
wrote:

On 21 May 2005 23:15:21 GMT, Bob Eager wrote:

So...are there any other, not too expensive, measuring gadgets that
will at least give a rough idea?


Try http://www.machinemart.co.uk/product.asp?p=010916213


Thanks...that looks useful.

I found the SAME item (listed there at about 15 quid plus VAT, total of
about 24 quid including shipping) for 39.95 plus 10.00 shipping plus VAT
(i.e. 57 quid) somewhere else!


Maybe.
But, on some loads, some of these can be very inaccurate.
Both the Lidl ones, and the one from maplin drastically over-read (double)
on many PCs, for example.
Fine on heaters, motors, lights, ...
  #9   Report Post  
Set Square
 
Posts: n/a
Default

In an earlier contribution to this discussion,
Ian_m wrote:

______

My power/consumption meter cost £6.99 from Lidls a year or two ago.
Works fine, enter your electicity cost per unit and it tells you the
total cost in £ and p. Currently on fish tank to see the running
costs. One complication is it tells you the power factor of the load,
but not how, if it does at all, affect the reading, because obviously
there are two powers now when power factor is not one, but
instructions don't tell you which. I suspect you have to multiply the
meter read power by power factor to work out your power in a domestic
environment, but I may be wrong.


Power factors of less than unity apply to reactive loads - like some type of
electric motors. [It's actually the cosine of the phase angle when volts and
amps are not directly in phase with each other]. If your device does the
same as mine, you can get separate reading for volts, amps, watts and power
factor. The power consumed in watts (and what you are paying for) is volts x
amps x PF. For a purely resistive load - like a light bulb, PF is 1 - so
it's just volts x amps.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.


  #10   Report Post  
Bob Eager
 
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On Mon, 23 May 2005 14:54:34 UTC, Ian Stirling
wrote:

But, on some loads, some of these can be very inaccurate.
Both the Lidl ones, and the one from maplin drastically over-read (double)
on many PCs, for example.
Fine on heaters, motors, lights, ...


I was aware of that. In my case, I'm more concerned with relative load
of the same appliance under differing conditions....!

--
Bob Eager
begin a new life...take up Extreme Ironing!


  #11   Report Post  
wig wig is offline
Member
 
Posts: 32
Default

Quote:
Originally Posted by Bob Eager
There was some discussion a while ago about a Maplin gadget that did a
fair job (I think) of measuring appliance power consumption.

I hate dealing with Maplin, and the discussion didn't cover a lot else
at the time.

So...are there any other, not too expensive, measuring gadgets that will
at least give a rough idea? I looked through the CPC catalogue but
didn't find anything (not that that means a lot).
--
Bob Eager
begin a new life...take up Extreme Ironing!
Can't you just use an ampmeter and measure the current?

P=IV so for 5 Amps
P= 5*240
P= 1200W

now to convert that into Kwh , I dunno maybe someone can help out?
1.2Kwh per hour just a guess
  #12   Report Post  
Andy Wade
 
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Default

Set Square wrote:

Power factors of less than unity apply to reactive loads - like some type of
electric motors. [It's actually the cosine of the phase angle when volts and
amps are not directly in phase with each other].


That's only part of the story for power factor, non-sinusoidal waveforms
(i.e. harmonic currents) being the other. Any electronic power supply
working from a single-phase supply and using a rectifier with a
capacitor-input filter (reservoir capacitor) - and that's most of them -
will only draw current from the mains near the peaks of the voltage
waveform. This gives a peaky or spiky current waveform which also leads
to poor power factor, despite it only having a small phase shift.

The more general definition of PF is true_mean_power / apparent_power,
the latter term meaning the product of the RMS voltage and RMS current.
Your meter or monitor instrument (& the Maplin one seems to be the
best) will display true power as W (or kW) and apparent power as VA (or
kVA). PF = W / VA. (The electricity company's meter reads kWh, so you
don't pay for the apparent energy you're not actually using - large
users excepted).

--
Andy
  #13   Report Post  
Bob Eager
 
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On Mon, 23 May 2005 13:01:16 UTC, Pete C wrote:

How about a recon electric meter, something like:

http://www.toolstation.com/messages.html?code=22833&mainWin=1

or maybe available from a boot sale or similar.


There's an idea!

Do you still have 12 PCs?


Bit more than that now...just got a bigger IP block!

OK, who are you?
--
Bob Eager
begin a new life...take up Extreme Ironing!
  #14   Report Post  
Bob Eager
 
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On Mon, 23 May 2005 17:30:05 UTC, wig
wrote:

Can't you just use an ampmeter and measure the current?

P=IV so for 5 Amps
P= 5*240
P= 1200W

now to convert that into Kwh , I dunno maybe someone can help out?
1.2Kwh per hour just a guess


Yes, I just about remember that from my electronics degree! But I want
to integrate a variable current over time...

--
Bob Eager
begin a new life...take up Extreme Ironing!
  #15   Report Post  
nick smith
 
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Default

Lidl did just a gadget a few months back - not sure how much it was but it did
integrate power over time - It was a 13 Amp plug one side and socket the other,
with a display and a few buttons, a bit like a timer.
Perhaps someone here got one and doesn't want it ?

Nick

"Bob Eager" wrote in message
...
On Mon, 23 May 2005 17:30:05 UTC, wig
wrote:

Can't you just use an ampmeter and measure the current?

P=IV so for 5 Amps
P= 5*240
P= 1200W

now to convert that into Kwh , I dunno maybe someone can help out?
1.2Kwh per hour just a guess


Yes, I just about remember that from my electronics degree! But I want
to integrate a variable current over time...

--
Bob Eager





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dennis@home
 
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"nick smith" wrote in message
...
Lidl did just a gadget a few months back - not sure how much it was but it
did
integrate power over time - It was a 13 Amp plug one side and socket the
other,
with a display and a few buttons, a bit like a timer.
Perhaps someone here got one and doesn't want it ?


It was about £6.49 and it appears to work well.
I use it to monitor how much power my various incarnations of media centre
PCs use.


maplin do http://www.maplin.co.uk/module.aspx?...38343&doy=24m5 but
its quite expensive and out of stock.


  #17   Report Post  
Bob Eager
 
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On Tue, 24 May 2005 06:51:41 UTC, "nick smith"
wrote:

Lidl did just a gadget a few months back - not sure how much it was but it did
integrate power over time - It was a 13 Amp plug one side and socket the other,
with a display and a few buttons, a bit like a timer.


It's OK, the Machine Mart one appears to do it.
--
Bob Eager
begin a new life...take up Extreme Ironing!
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Ian Stirling
 
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dennis@home wrote:

"nick smith" wrote in message
...
Lidl did just a gadget a few months back - not sure how much it was but it
did
integrate power over time - It was a 13 Amp plug one side and socket the
other,
with a display and a few buttons, a bit like a timer.
Perhaps someone here got one and doesn't want it ?


It was about ?6.49 and it appears to work well.
I use it to monitor how much power my various incarnations of media centre
PCs use.


To bang on about this again - it may well be overreading by up to double.
The Lidl one I got does, on many PCs.
(Well, 2/3 power supplies I've tested)
(both of 2 Lidl units do, indeed)
  #19   Report Post  
Ian Stirling
 
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Andy Wade wrote:
Set Square wrote:

Power factors of less than unity apply to reactive loads - like some type of
electric motors. [It's actually the cosine of the phase angle when volts and
amps are not directly in phase with each other].


The more general definition of PF is true_mean_power / apparent_power,
the latter term meaning the product of the RMS voltage and RMS current.
Your meter or monitor instrument (& the Maplin one seems to be the
best) will display true power as W (or kW) and apparent power as VA (or
kVA). PF = W / VA. (The electricity company's meter reads kWh, so you
don't pay for the apparent energy you're not actually using - large
users excepted).


The maplin one I have misreads in a similar way to the Lidl ones.
Indeed, I bought the Lidl one in the hopes that it'd be more accurate
than the maplin one.
  #20   Report Post  
Andy Wade
 
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Ian Stirling wrote:

The maplin one I have misreads in a similar way to the Lidl ones.


What way is that - and how much in error? (Genuine questions.) I have a
Maplin one and whilst I haven't rigorously assessed its accuracy it does
give quite plausible readings on low consumption low PF loads (such as
CFLs).

--
Andy


  #21   Report Post  
Ian Stirling
 
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Andy Wade wrote:
Ian Stirling wrote:

The maplin one I have misreads in a similar way to the Lidl ones.


What way is that - and how much in error? (Genuine questions.) I have a
Maplin one and whilst I haven't rigorously assessed its accuracy it does
give quite plausible readings on low consumption low PF loads (such as
CFLs).


Double - on 3 similar PC power supplies.
I was concerned, as it was reading my PC with one drive and no monitor at
100W, which seemed unlikely.
A few minutes later with a few resistors and a scope, produced waveforms
for current, which looked rather odd, and seem to be the reason it misreads.
These things will only sample the current so often, and it seems not quite
often enough for some loads, so they make mistakes.

(For all other devices including various sizes of SMPS it worked fine)
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