Re: Remote electricity usage monitoring

[Kevin Hawkins <lists@xxxxxxxxxxxxxxxxx>]

Hi Richard,

The pulses from the sensors can be interpreted to provide two types
of information - firstly a realtime usage by measuring the period of the
waveform and secondly, by counting the pulses, a cumulative usage. The
former is more awkward but there are off the shelf devices that can do
it.   For the latter, which is the most common requirement, the easiest
way seems to be to feed the pulses into a standalone electronic counter
and periodically read this counter from a PC software application.  That
way if the PC is turned off you don't lose information.   There are many
data loggers available that will do this and also there are basic
counters like the VIOM or Netiom which you can query by Serial/Ethernet
respectively.

Once you got the meter pulses into a readable counter either via
serial or Ethernet it's a fairly simple task to create whatever app you
want to store the values periodically into the DB.  Just make sure you
read the counters frequently enough before they cycle around.  Some of
the commercial data loggers can run many days/weeks/months in this
respect - depending on how much memory they have.  A Netiom uses 16 bit
counters - 64K pulses.  I monitor several 'rings'  using a single xAP
Netiom (16 inputs).  I have installed the more sensitive pulse output
devices which in parctice generate a pulse every second or so in high
usage - this has ramifications on the size of the counters you need and
how often you will reset, or read them (in my case they cycle about
every day)  .  Some of my devices are the standalone consumer meter type
and some are just small DIN rail mounted counters. I display the current
'meter readings' and cost in a web browser using xAP Floorplan and ,
although I personally don't do it you can write the data from there to
an SQL DB too.

I have dabbled with the 'realtime' consumption side too using a VIOM
where the edge triggers start/stop a fast timer, and you have to read
the value before it starts again. It seems to work quite well but it is
quite serial port intensive as my pulses are sometimes less than half a
second apart and all this has to be triggered using several 'events' via
a slowish serial port. It would really benefit from faster/more
tailored  hardware and of course there are such devices on the market.

Kevin




Richard Parker wrote:
> Hi all,
>
> I've posted a similar query to this before, but figured a better
explanation
> of the problem might actually help :)
>
> Basically, we live in an apartment block. Our main electricity meter
is
> stored in a communal utility cupboard serving 6 separate apartments,
right
> down the hallway. Installing anything into this cupboard is out of the
> question.
>
> My goal is to be able to monitor electricity consumption within my
apartment
> and log this information into SQL, similar to the setup at http://bwired.nl.
>
> I have considered installing a local power meter module into my
consumer
> unit but this still presents the nasty technical challenge of
converting the
> optional pulses into something that can be read from a PC. I'm not
adverse
> to doing this but wondered if there are any alternative products or
guides
> that may be useful.
>
> Many thanks
>
> Richard
>
>
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