Any good electronics guy should be able to build his own analog power
measurement device fairly cheaply these days, and interface to
computer A/D if useful too. There are numerous Analog Devices chips
available. If high frequency transients are important then a 4
quadrant analog multiply chip can do the power computation very fast.
I took a simple route. I bought a KLL A WATT model P4400 power/energy
meter, which has been handy for looking at appliances. Here's the
brochure:
http://www.p3international.com/brochures/P4400.pdf
Theses are readily available online for under $30, but I think I
bought mine at Wal-Mart:
http://www.google.com/products?client=safari&rls=en&q=%22kill+a+watt%
22+power
+meter&oe=UTF-8&um=1&ie=UTF-8&ei=mESyS4GbOIyKswOircDMBA&sa=X&oi=product_
result_group&ct=title&resnum=1&ved=0CCIQrQQwAA
http://tinyurl.com/yamunyg
For specifications on similar P3 products:
http://www.p3international.com/products/index.html
The P4400 uses a 78M6612 chip, See
http://www.edn.com/blog/1470000147/post/1500044550.html
for a look inside.
The 78M6612 is described here:
http://www.teridiansemiconductor.com/products/energy-automation/
energy-measurement/6612.php
http://tinyurl.com/yfvpyuw
I think a reasonable approach to power measurement is to measure wall
socket power prior to input to any power supply. It is then possible
to add HF bypass capacitors, and in-line inductors if required, to
the secondary of power transformers or power supplies in order to
smooth the AC input demands adequately for accurate power/energy
measurement.
If calorimetry is to be used it is then just a matter of placing any
power electronics after the power/energy meter inside the calorimeter
in order to get good measurements.
There are a variety of power/energy meters out now that have computer
interfaces.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
