Re: Measuring Power dissipation emperically

Jon Slaughter wrote:

You could stick in a box, and watch the rise of the air temperature in the box.

Then repeat the experiment, but replace your device with a resistor. Adjust the current to get the same rise in temperature.


Yes, this is what I'm talking about with water. Air has less thermal inertia so the measurements will be more unstable. (unless you can control it precisely)

Also, with water its easier to use the specific heat capacity to get another measurement. (easier to measure water's mass and it has extremely high thermal inertia)

I wouldn't recommend water. Even if you use distilled water, you risk that residues on the PCB dissolve in water, and create free ions. This ruins the board, and may even create significant leakage currents.

Some folks have put their PC motherboard in regular cooking oil, and it works fine. Of course, it's really messy, so you'll end up sacrificing the board. Here's an example:

http://www.tomshardware.com/2006/01/09/strip_out_the_fans/page11.html

Using a insulated box with air is certainly the simplest. You can reduce the errors by measuring inside and outside temperature, and averaging the delta over a long period. Do the same with a resistor, possibly mounted on the same (empty) PCB, or same heatsink, and match the current until you get the same delta.

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