On 17/03/2015 18:58, john james wrote:


"whisky-dave" wrote in message
...
On Monday, 16 March 2015 18:16:40 UTC, john james wrote:
"whisky-dave" wrote in message
...
On Friday, 13 March 2015 19:30:12 UTC, john james wrote:
"whisky-dave" wrote in message
...
On Friday, 13 March 2015 12:56:31 UTC, Roland Perry wrote:
In message
, at
04:05:22 on Fri, 13 Mar 2015, whisky-dave
remarked:
It is possible with just one TV but not with two.

I would phrase that as "may" be possible, but very unlikely.

It would be easy enough with just one as long as the TV
is showing a broadcast channel and has a backlight that
changes with what is on the screen.

But how will you measure the backlight current ?

It's between 1/3 and 2/3 (depending on the viewed content) of the
set's
overall consumption.

I'll ask again how will you measure the *backlight* current.

Unless I'm very much mistaken there's a meter
looking at the household's total consumption - one contributor to
which
is the TV.

So on the TV you have a silent B&W movie and next is the lastest
action
film.

As the volume goes up and down this also changes the current
consumption
of the TV.

Not by as much as the backlight changes with TVs that change
their backlight current with program content light levels tho.

The backlight current doesn't change anywhere near the amount you
think it
does.

It does actually and that is easy to measure to prove that.

So show me the results......

I don't have a TV that varies the backlight with what's show on the
screen. My TV is a gigantic glass tube TV than hasn't even been
turned on for maybe 8 years now. I don't watch any TV live, I watch
what the PVR records on one of the 24" wide screen LED monitors
on the desktop which does everything, including being the PVR.

Backlight currents have reduced by about 50% in the
last 2 years so all your reesults will be worng anyway.

What ? All that matters is that they vary with what is on the screen.

Also while watching the TV I might be using my computer increasing
teh brighness of the screen the power consuption nof my iMac almost
doubles and almost doubles again if I push teh grahics
processor. Yep
I've had 400 FPS on my retina 27 inch imac, that's when the fan
kicks
in,

Yes, but those changes are much slower than the backlight current
which is changing as the scenes change with the TV content.

My computer is far faster than my TV screen.

The rate at which the screen content changes isn't.

400 FPS on my TV is faster then 60HZ.

That isn't the rate at which the screen content changes.

and what do yuo think the backlight is doing then.

It doesn't vary at anything like that rate because what
is on the screen doesn't vary at anything like that rate.


Rubbish.


another vairiable, burning a DVD which I know takes an extra 5W of
power
which obviously all comes from the household's total consumption,

Yes, but again, much more slowly than TV scene changes.

Irrelivant.

That is how you work out what you are seeing current
wise is due to.

so what is this current ?

Varies with the design of the TV obviously.

and the washing machine cycle changes,
again changing total current consumnption,

Yes, but again, much more slowly than TV scene changes.
Those are just a few steps in the total house consumption.

if I open the fridge/freezer a light comes on.

Yes, but again, that is just a step change,
just like other lights being switched on.

they are all step changes so are the 7-segment displays on my clock
and
washing machine.

And the change in the backlight current

what is this change ?

with a TV that
changes the backlight with the screen content isn't.

isn't what ?

Isn't a step change.

When my landline phone takes a message that
also takes more current, even the ringing would.

Again, both with quite characteristic waveforms.

No where near enough to be measurable by a smart meter.

The phone never rings for that long compared with the TV.

it doesn't have to, donl;t forget you're only sampling what curretn
the meter is reading in a fraction of a second.

That isn't how the electricity supply authority smart meters work.

They integrate the current over time because that is what you pay for.



They integrate the energy used over time because that is what you are
charged for. That changes depending on the voltage on the supply which
changes with demand and with things like solar flux acting on solar
panels nearby and on wind, etc.