mark wrote:
wrote:
Grunff wrote:
I'm
wondering if there isn't another way of doing the integration. If
that makes sense.
there is, use an opamp integrator. No sampling, along with the
errors
that introduces.
haha, yes, nice one. You think that an analog integrator
isn't going to have errors? Especially accumulated over
minutes? 
every method on the planet has errors. Try not to be dumb. We just need
to get in below 1%.
Digital sampling is going to be especially problematic with a spikey
load, as the digital sampling has to be so fast it maps the spikes out
accurately, ie a great number of samples per spike so the spike's shape
is followed faithfully throughout. This is necessary to come in at
below 1%.
It is difficult to achieve this unless you know the highest possible
frequency component of said spikes. In practice, if you dont, you have
a mathematical problem to pick the sampling frequency needed to keep
total error budget below 1%.
We know the spikes occur at upto 10kHz, but that is the repetition
rate, not the highest spike frequency component, which inevitably will
be orders of magnitude higher.
Analogue integration has issues like every method, but its relatively
easy, simple, and low cost, and coming in at 1% is practical.
The data logger is the best idea, just record the I&V
waveforms over the period under question then do everything
else numerically.
There might be a bit more to it.
BTW v and i need to be multiplied before the power product is
integrated. Since you need 1% accuracy you will need to measure v, you
wont do it just measuring and integrating i.
I always tell people not to ask electronics qusetions in uk.d-i-y, we
have a remarkable amount of expertise on diy, building etc, but this
can lull some into imagining this is a group with expertise on tronics.
While we do have some, most do not, and the truth does not fall out
clearly like it does with other topics. Only if you know the answers
will you recognise in most cases. sci.electronics.design is the place
to go for this stuff.
NT