Power meter

jabaroon

Hi All,

I got one of those gadgets that you clip around the cable coming out of your meter. It then transmits a signal to a base station to tell it about your power usage. I think its about every minute it takes a reading or something like that.

Just wondering if anyone knows what type of technology is used to take the measurement. As I say, its just something that clips around the power cable, no physical connection required.

Wonder if its accurate?

Cheers,
Jab

Davy

Ammeter. idea here

A grip on ammeter is more like what is used. Normally two jaws that open and close around the cable. http://en.wikipedia.org/wiki/Clamp_meter

jabaroon

cool! thanks!

Stoner

it measures the strength of the electric field around the cable, the more current used (i.e the more power you consume) the stronger the field.

RoundyMooney

The only thing it can't measure is voltage, so assume the power indicated may deviate 10% either way and you should be fairly on the nose.

arse..biscuits

RoundyMooney wrote: »

The only thing it can't measure is voltage, so assume the power indicated may deviate 10% either way and you should be fairly on the nose.

It assumes 230V so not 100% accurate

DublinDilbert

jabaroon wrote: »

Hi All,

Just wondering if anyone knows what type of technology is used to take the measurement. As I say, its just something that clips around the power cable, no physical connection required.

Wonder if its accurate?

Cheers,
Jab

A hall effect device is generally used, although if you just want AC you can just use a pick-up coil.... Most of the cheap clamp on ammeters, just measure AC as they use a pick-up coil. the more expensive ones do AC and DC and use a hall effect device.

SparKing

Well not to contradict anyone but is it not current transformer CT that is used and a transmitter to send readings to a base station, coincidentally I bought one today to check the accuracy of a fixed sub ct meter, it says on the box that it is not 100% accurate but it'll give me an idea if the other meter is way off, it's absolutely perfect for the domestic user who wants to check how much power each appliance uses, the one I got also works with 3 phase.
I'm well impressed!

Michael Collins

Yep, most of them work on a current transformer (CT) principle - hence using the magnetic field. As such, they will only work on AC - as DublinDilbert says they need a Hall Effect sensor to work for DC current.

They don't have to implicity assume anything about the value of the voltage but they do assume the current is sinusoidal.

They're not much use for domestic situations as you nearly always only have access to the whole cable, and not the individual phase and neutral - so since CTs will only give you the net current in the cable, it'll read zero. I've seen socket splitters for USA sockets - it just splitts the phase and neutral coming out of the socket, allowing you to clamp around it, then you plug the device into the other end. I've never seen one for Irish type sockets tho...

stylers

the cheap one's use a small clip on CT (current transformer). be careful of working on them while clipping it around the cable, as there may be no load resistor across the CT (well my one had none anyway), which could give rise to cracking high voltages at the sensor plug :eek:

SparKing

Michael Collins the unit is one you install into your fuse box or at the main meter position and it clips around the live wire only it then transmits current units in kW, kW/h or € (you can set a unit price) to a receiver which is mobile and you can wander around turning appliance on and off to see how much power they use, saw them in Maplin for €60 which is €10 less than I paid in the electrical wholesaler surprisingly. The one I got is called an Efergy Elite.
Oh yeah it Doesn't assume 230V, You set the voltage yourself, though the default setting is 230V

northdublin

we have one of these set up in the shop, its called an owl energy meter and like to op's one it clamps around the live and additional clamps can be got for 3 phase. the lads who i work with say they are quite accurate and i think they have tested it along side more specialist clamp meters to compare it.

Michael Collins

SparKing wrote: »

Michael Collins the unit is one you install into your fuse box or at the main meter position and it clips around the live wire only it then transmits current units in kW, kW/h or € (you can set a unit price) to a receiver which is mobile and you can wander around turning appliance on and off to see how much power they use, saw them in Maplin for €60 which is €10 less than I paid in the electrical wholesaler surprisingly. The one I got is called an Efergy Elite.
Oh yeah it Doesn't assume 230V, You set the voltage yourself, though the default setting is 230V

That's pretty nifty. I saw them advertised alright but didn't bother looking at how they work. Must consider investing in one...

Sorry about the confusion above, I was talking about the clamp meters.

fishdog

They are €49.95 at the moment in Argos at the moment. The make is "Owl" and they can be set for a day and a night tariff. They can be set to read, kW, euros, and CO2 emissions as well as constantly displaying time, date and temperature. They update ever 2 seconds.

RoundyMooney

Eamon Ryan should subsidise these. They encapsulate pretty much all of his mooted smart meter advantages (in terms of monitoring the supply usage anyway) with the exception of his daft assertion that they can automatically control house appliances.

And they'll make people ever conscious of what they're burning at any given time, years in advance of the rollout of smart meters (which if they run with the prototype ones-won't do half of what was promised they would do-they are primarily utility friendly devices).

Can someone link me to these please?

Davy

I think that would be a good idea, they aren't that expensive at the moment even but he he got electricity supply companies to sell them direct at a reduced price. Could even pay them with the bill etc. Seems like something to complex for him though.

A few of the options:

http://ecologics.ie/home/efergy-electricity-display-device/

http://www.theowlireland.com/index.php.htm

http://www.energymeter.ie/index.php/buy-now

Kanedmick

Reviving old thread - sorry!

I bought one of the Efergy ones in Maplins and not thinking much about it as it seems like an ideal gift. However, I am a little stumped.

Will it work in an apartment - as the meter is usually located in the basement. Can it be attached to the Fusebox?

Thanks for looking!

Davy

Kanedmick wrote: »

Reviving old thread - sorry!

I bought one of the Efergy ones in Maplins and not thinking much about it as it seems like an ideal gift. However, I am a little stumped.

Will it work in an apartment - as the meter is usually located in the basement. Can it be attached to the Fusebox?

Thanks for looking!

Depending on how big your block is, it may or may not. In the majority it wont. If your ground floor you would be ok.

You can put it on your own fuse board, but dont go playing if your not familiar with it. Its handier to put on at the meter, as their isnt really a place to get shock unless you start braking the meter cover etc. At the board, you will have to remove the cover to get the clamp on, and this is really meant for a electrician only.

Kanedmick

Thanks Davy. That's a straight enough answer. If you are an apt dweller, not really an option unless u r an electrician or u fancy ur chances Russian Roulette style! ;-)

Pity that. Is there one that works for apts? Would have thought there would be as almost all apts, in this country at least, work off electricity almost exclusively - except for those on gas heating obviously.

Anyone see an alternative to the meter only ones mentioned above?

Ta!

Davy

Just get any one, and get someone to put it in for you simple as. Will only take 5 minutes tops

Bruthal

SparKing wrote: »

Oh yeah it Doesn't assume 230V, You set the voltage yourself, though the default setting is 230V

The lads are correct saying it assumes 230v though, even of you can change the voltage setting, in that it wont give an absolutly true KWH reading measuring only current, it assumes the supply voltage will stay fixed.

In an apartment it can be put onto the live feed into the main switch, but as said, its not a job for the diy man. It would work on the main neutral as well assuming no mad earth leakage in the installation. But on the Live/Phase is recommended.