On Thu, Nov 17, 2011 at 09:12:54PM +0000, Wayne Stallwood wrote:
On 17/11/11 09:21, Mark Rogers wrote:
On 15/11/11 23:32, Wayne Stallwood wrote:
Actually the point of reading the pulses from the meter is that the meter is pretty damn close to being 100% accurate in real terms and is 100% accurate in terms of what you are paying for.
Absolutely, but I can still verify the data coming from the CT [*] by manually checking the meter periodically. If there's a big discrepancy I can adjust for it (and possibly buy the OptiSmart if I need to), although if the CT measurements aren't accurate then any hope of sub-metering with extra devices around the house goes out of the window. (Also, for this reason I wouldn't want to just have pulse counting at the main meter and use the CT to sub-meter (eg) my server, because if the CT would give inaccurate reading at the main meter then it'll still be giving inaccurate readings at my server but I won't know about it.)
To be honest the supplied CT in the kit isn't really suitable for measuring the consumption for a single device or a group of devices anyway, you need the IAM's for that.
The current transformer needs to be attached to a cable carrying a single pole (Live) of a single phase...If you attach it to say a mains flex feeding a 4 way extension bar then the two poles (Live and Neutral) of a single phase in the flex have opposing fields and therefore cancel each other out.
I've never really understood the utility of any of the devices being promoted by the electricity companies which all (as far as I understand them) indicate your total electricity consumption. That's next to useless as it gives you no real clue as to what is actually eating your electricity.
In fact unless one can monitor in considerable detail (e.g. have a monitor on each circuit of the consumer unit, or even smaller areas than that) I can see very little point at all.
I do have a plug in device for measuring the consumption of whatever is plugged in to a single socket and that can be (somewhat) useful for checking how much something like a PC is consuming though of course the accuracy can be poor with switching supplies etc.
I've yet to see anything which indicates how much electricity the lights (for example) are using. At least not something available cheaply and to the general public, obviously it can be done if one uses a multimeter with AC ranges, but that's hardly what one wants.