I would think you would be better off trying to keep the temperature as low as possible for standby operation so that the components that are radiating the most heat (i.e. consuming the most power) will stand out from the background on your thermal camera. Am I wrong?
The temperature difference between a device and its surroundings will stabilise at a more or less constant level regardless of the actual temperatures involved. If the board's at 20 deg C and the part is at 20.1 deg C, then cooling the board to (say) 15 deg C would mean the part ends up at 15.1 deg C. There's also the practical difficulty of cooling the board and keeping it at a very constant, uniform temperature.
It may be that a TIC can more clearly perceive small differences at lower temperatures, but there wouldn't actually be a larger difference to measure in absolute terms. So, I think the best bet is to seal the board into a box with very still air (at whatever the ambient temperature in the lab ends up being), give it plenty of time to stabilise, then cut the power and observe what happens.
another thing you can do to increase the contrast is to spray it with freeze spray, the items generating heat will more rapidly return to ambient,
Nice idea - I've seen the effect - but in this case I think the total amount of power involved is too small. The temperature differences which exist across the board as a result of being blasted with freezer spray would absolutely swamp the tiny amount of heating I'm expecting to see.
Keep the camera idea but instead spray the board with isopropanol or something similar. The alcohol will evaporate first from the hottest components.
I'm looking for about one surplus milliwatt... I doubt it'll evaporate anything much.
This is why it's a good practice to put 0 ohm jumpers on the power traces for different "blocks" of the circuit, you can always solder them off and measure which area of the circuit is consuming the power. Also handy when you're testing step-up/down modules that are feeding the rest of the circuit, so you can make sure you won't break anything if the voltage is too high for example.
Agreed; most of the power domains on the board are switched under software control anyway.
At the opposite end of the scale in power terms, I did once learn a very valuable lesson about 0R links, namely: they're not 0R, or anywhere close. If you have a CPU core drawing several amps at, say, 1.2V, you can't put a 0R link in the way... I did, once, and the core voltage dropped to about 1.05V. Amazingly it kept working just fine, but a thick, solid copper wire link soldered in place of the 0R resistor made a huge difference to the voltage drop.
In principle this should work. Almost the same principle is often used for digital astrophotography (e.g. http://keithwiley.com/astroPhotography/imageStacking.shtml).
That was my first thought too, and thanks for the link - it confirms that software intended for astrophotography should, in theory, be able to pick out the subtle variations between frames that I'm looking for.
I don't suppose there's any particular tool which you can recommend for this purpose...?
0.5mA isn't that much, and could just be due to either the battery self-draining or the resistance of the switch circuitry. It's possible it could be seen with a TIC, but unlikely.
It's definitely a real current draw, I'm supplying the board from my HP 6632B which has a usefully accurate meter built in. I expect it to be a challenge to see the effect with a TIC, but that's half the fun!