Smart enery monitors

I've often wondered about one of those remote monitors showing live electricity usage. The ones I see all seem to have something clamped around the supply cable to measure the 'flow', are these accurate?
I'm pretty sure we've got a smart meter, is there a device I can get to communicate directly with the meter?
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R D S wrote

Fairly, you can check them by a timed run of e.g. a 3kW kettle, they might be less accurate measuring a bunch of wall-warts.

If you've got a smart meter, you should have an in-house display showing live power usage (W or kW) and historic energy usage (kWh)
Mine's like this ...
<
http://www.consumerfocus.org.uk/files/2012/05/in_home_display3.jpg

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On Sun, 23 Feb 2014 15:14:21 +0000, Andy Burns wrote:

That'd be fine, i'd like to measure the greedy stuff and note the times we are using in excess.

I've not got an in house display, First Utility promised us one when they changed the meter, but it was never forthcoming.
They used to have (almost) live reporting where you could check usage on the net, but they canned that and i've since changed supplier.
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Do these new smart meters we are going to get interface with a computer so we can see the textual output, not a pretty picture that we blind cannot access? Brian
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On Sun, 23 Feb 2014 22:36:42 -0000, Brian Gaff wrote:

They might have computer interface but even if they do I doubt the data format will be published and it will vary from meter maker to meter maker.

Be a doddle for my Perl/PHP set up to output text instead of a graph but 1440 data points in a day might take a while for a screen reader to speak. B-)
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Smart meters are the thin edge of the wedge in a whole new technology that will shortly be rolled out. It is being piloted right now.
The possibility exists to cut off electricity for non-payment and to charge more when energy is in short supply. For anyone on the ball, the possibilty will exist to save a lot of money and so of course will the energy companies. http://en.wikipedia.org/wiki/Smart_grid
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Smart meters are for the benefit of distributors, not you. The ability to cut you off without having to visit you is one of the key features the distributors are after. Just wait until their control systems get hacked, and half the UK suddenly has its supply cut off, followed by trashing of the control system so it can't be switched back on.
If Smart metering was aimed at the consumer, you would have got features such as selecting the cheapest supplier to run your washing machine this evening, or given you want to use your washing machine in the next 48 hours, who will sell you the cheapest electricity at a time of their choosing to do this.
No, none of the potential consumer benefits side is even being considered.
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On 28/02/2014 18:32, Andrew Gabriel wrote:

And they are also harmfull, the radiation and all that ....
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Are they really capable of switching the power off, surely must contain a 100 amp relay etc. And surely they won't be doing that on just a whim what with some people using power for medical devices etc?...
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tony sayer wrote:

Yes, my electric one has a 100A contactor, and gas one has a battery powered valve.

I presume not, they can always bash the front-door down if they can justify cutting you off. There is always a risk they get hacked, but if half the country is off-supply, I'm sure I could think of ways and means ...
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On 01/03/14 10:22, Andy Burns wrote:

Google for
scada hack
and read just the first page.
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http://en.wikipedia.org/wiki/SCADA
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tony sayer wrote:

    Of course they will, they have all the data on the computer which is infallible.
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On 23/02/14 15:07, R D S wrote:

They should measure amps accurately but not necessarily power.
Voltage variations will be one source of error and the powerfactor will be another, though even with a house full of computers, the latter is unlikely to be much more than 5% out. So all in, probably good to within 5-10% at worst.
The other option, if your meter has a pulse LED is to use one of these:
http://www.currentcost.com/product-optismart.html
That will be as accurate as the meter and will measure true power (providing the sensor does not miss any flashes).

That I do not know.
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On 23/02/2014 15:19, Tim Watts wrote:

I looked at this recently for a smart meter attached to a PV installation. I found 3 ways of getting the reading out of the smart meter. (As Tim noted, using the meter reading should be more accurate than a clamp-on ammeter. If this is your supply meter, whether or not it's accurate, it will at least be the figure used to bill you. :)
Firstly, as also noted above, is a detector that captures flashes on the pulse light, possibly one flash per 1 Whr/3.6kJ (the figure can vary, but should be printed on the meter next to the light).
Secondly is to get the same pulse signal on an electrical contact. This is the technique the PV installation I looked at used to drive a remote display. However the connections are behind the same sealed cover that protects the metered supply connections so if this is the supply meter you'd need to get the supply company involved to make connections.
Both of these techniques just issue a pulse per energy unit consumed. It's up to your monitoring device to count pulses accurately. If you want your monitoring device to show the same figure as your meter you'll need to put the current meter reading into your device when you start using it (assuming it allows you to do this).
The third technique overcomes this limitation. This is to use an IrDA (infra-red) output from the meter. Again, you use a stick-on detector (infra-red, of course) to pick up the pulses, so no messing around behind sealed covers is required.
However the IrDA signal isn't just one flash per energy unit, it encodes the meter reading (plus some other stuff) so your monitoring device gets the same information as the meter shows on its front panel display.
Not every smart meter offers all of these methods so you'll need to google your smart meter model number and see what it does. You can also google to see if anyone has already interfaced to your meter. (Despite Dave's misgivings I found plenty of information out on the web for my meter/display devices.)
As an example, or for people wanting to build their own monitors the following links describe an Arduino-based IrDA monitor for the meter my PV installation used: http://openenergymonitor.blogspot.co.uk/2012/07/reading-watt-hour-data-from-elster.html (CT in this link = Current Transformer, i.e. the gizmo you clamp on your supply cable for basic monitors.) http://www.rotwang.co.uk/projects/meter.html
The following links have some C code for decoding IrDA data (e.g. if you wanted to use something other than an Arduino): http://cgi.csc.liv.ac.uk/~greg/projects/rdmeter.html http://cgi.csc.liv.ac.uk/~greg/projects/rdmeter.c (They were working a few days ago but the site was down at the time of writing this post. Hopefully it will be back up again later.)
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