"Andy Hall" wrote in message
...
On 2006-07-26 08:34:18 +0100, "Andrew Mawson"
said:


"Keith D" wrote in message
...
I would like to have a data logger that can track the KWs being
used
in my
home. I need to know load times/days etc. I have seen a number of
items that
do this by attaching to the power cable from the consumer unit
and
then
sending this data using RF to a display unit.
(http://www.electrisave.co.uk/) but this does not have a PC
interface so I
cannot use it to log data over a long period of time.
Question: How does this device collect/measure the total
electricity
used?



I have a secondary elctricity meter (that was originally a coin
operated one) that has had the coin mech taken out and a slotted
LED
sensor put on the disk, which via an optoisolator drives the
interupt
bit of the parallel port. I've been logging electricity (and water
too) using this method for over 10 years now.

AWEM

Interesting. One interrupt per revolution of the disk?






Yes, and I use a simple RS transducer to give me water rate usage,
though that has to have a 'divide by 100' circuit in series due to the
rapid rate of revolution. The software (which I wrote) does simple
zone control on my central heating, and also has provision to monitor
gas, but I've never found a suitable sensor.

AWEM