Hi Brenton,

thanks for the confirmation.

Initially I thought I had it all sorted but then started to struggle while
thinking about the math required for the conversions.

I think my biggest issue was I had accepted power as the instantaneous
value where it is actually the energy for a given second.

Ok I guess to refer to watts as the instantaneous value but not ideal when
it is needed to be used for calculations.

Justin





On 21 May 2016 at 06:18, Brent Brown <brent.brown@clear.net.nz> wrote:

> Hi Justin,
>
> Yes, there certainly is a lot of mixed up language out there when it come=
s
> to
> describing power and energy. But everything you say sounds correct to me,
> well at
> least from a skim read ~ good work!
>
> Here in NZ the domestic user buys, and sometimes sells, electricity in
> units of kWh.
> I believe the most common pulse output from a meter is 1000 pulses per kW=
h
> (=3D1
> pulse per Wh).
>
> And yes, the unit is effectively energy/time * time (where the divide and
> multiply by
> time cancel out) but it's relatively easy to understand and avoids
> introducing another
> term to the consumer, ie. Joules. Take for example a 1kW bar heater
> running for
> 1hour =3D 1kWh... most people can visualize/appreciate that, even though =
a
> 1kW bar
> heater is not as ubiquitous as it used to be.
>
> On 21 May 2016 at 1:59, Justin Richards wrote:
>
> > I am sure I had this well understood once but it seems I need a revisit=
..
> > However, the texts are ambiguous.  They refer to watts as the
> instantaneous
> > energy but I think it is energy per second.
> >
> > Assuming DC supply of 1 volt across and a purely resistive 1 ohm load
> i.e.
> > 1A flowing thru it.
> >
> > Being technically pedantic are these statements correct:-
> >
> > 1. 1 watt =3D 1 joule per second
> > 2. a rate of 1 watt is the POWER
> > 3. energy is consumed at a rate of 1 watt
> > 4. after 1 second the load has dissipated 1 watt.second.  The seconds
> > cancel so (1 joule / sec) * sec =3D 1 joule
> > 5. after 5 secs it has consumed 5 watt.seconds =3D 5 joules
> > 6. after 1 hour it has consumed 1Wh which is equal to 3600 watts.second=
s
> or
> > 3.6 kJ?
> >
> > whereas these statements are incorrect:-
> >
> > 1. a rate of 1 watt is the POWER CONSUMPTION
> > 2. energy is consumed at a rate of 1 watt per second.
> > 3. after 1 second the load has dissipated 1 watt
> > 4. after 5 secs it has consumed 5 watts
> >
> > I ask because I would like to build a device similiar to a hackaday
> project
> > called Internet-of-Things-Power-Meter which counts LED pulses produced =
by
> > modern house power meters.
> >
> > On the hackaday project (and elsewhere) they state "Modern power meters
> > have a LED blinking every time a Watt is used" I have yet to check but =
I
> > think more correctly it flashes once every 1Wh. So I would like to
> convert
> > this to watt.seconds (the so called instantaneous power) , Wh and daily
> > consumption.  I assume daily consumption could be stated in terms of Wd
> or
> > watt.day.
> >
> > Am I on track?
> >
> > Justin
>
>
>
>
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