Andy Dingley wrote:

The reason for using an analogue multiplier is when the power factor
(i.e. the ratio between the measured values) is all over the place.
This may need to be "sampled" at a high rate, so that appropriate
pairs of values are multiplied together.

Ah, ok, gotcha.


Your "spiky" load is probably not that spiky, compared to this
requirement. I'd expect you could easily sample and mulitply
digitally, with a speed well in excess of the experimental variation
(You'll need to actually work this out anyway, to do your error
analysis).

I think based on all the good advice so far, I'm going to go for a two
pronged approach. I'll set up a calorimiter, and use the resistor method
discussed elsewhere in the thread, and I'll also get a data logger (as
fast as I can afford) and do the measurement that way as well. Should be
interesting to compare the results.


--
Grunff