It happens that The Natural Philosopher formulated :
I wonder why they mentioned 3ph right at the beginning of that, then
swapped midway to domestic supplies which were presumably single phase?
I have tested both of my meters just as thoroughly as possible and
found no obvious calibration errors. The rest of the Smart is sadly
I don't understand why the measuring part of the meter isn't exactly the
same as the previous style of digital meter, like wot I have on my property
or perhaps these read wrongly as well
No meter can measure equally accurately in all conditions, so all will
read wrong to some extent, which is why they allow a tolerance of
accuracy. They are suggesting these all electronic Smart Meters can
miss the sudden surges in demand, I would suggest the older mechanical
meters missed even more.
Reading up a bit on this subject, there is a meter fault known as
creep, where the meter will continue to turn slowly, despite no load.
That is not the same as the disc doing a full revolution or completing
a revolution, after demand has ended.
On Wednesday, 8 March 2017 05:07:30 UTC, Harry Bloomfield wrote:
There was permanent magnet to stop this sort of thing which was caused by the meter working as an induction motor due to the voltage coil.
The magnet also acted as a brake stopping the disk almost immediately when the current went off.
This gave rise to the urban myth that putting a magnet on top of the meter slowed it down.
The permanent magnet provides a braking force that's proprotional to
the speed of the disk. As you say, it's stops the disk spinning like
an induction motor and reaching 3600 rpm or whatever.
But it will have virually no effect at low speeds, because the eddy
currents that it induces get lower as the disk spins slower. So I
don't think the permanent magnets stop disk creep (if it's ever
actually a problem in the first place, which I'm starting to doubt
They sometimes (don't know how often, I've only seen one example) have
a shading coil which provides an additional magnetic field that's out
of phase with the voltage coil. I believe this is designed to just
overcome frictional losses so that very small loads are measured. But
sometimes (again, don't know how often), this makes the disk creep. So
some disks have a hole or slot drilled into them at a certain
position, and they will creep round to that point at zero load.
I've only seen one example though, and that was a very old 240v single
phase meter back in the 1970s (the meter would have been much older
than that). So I could be talking about a very rare behaviour on a
particular type of electromechanical meter.
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