I've often wondered about one of those remote monitors showing live
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?
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.
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.
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
No, none of the potential consumer benefits side is even
[email address is not usable -- followup in the newsgroup]
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?...
Yes, my electric one has a 100A contactor, and gas one has a battery
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 ...
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:
That will be as accurate as the meter and will measure true power
(providing the sensor does not miss any flashes).
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
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:
(CT in this link = Current Transformer, i.e. the gizmo you clamp
on your supply cable for basic monitors.)
The following links have some C code for decoding IrDA data
(e.g. if you wanted to use something other than an Arduino):
(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
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