Temperature Tests: Investigating a Surprising Result

[grillomartin]

Hi everyone.
I am performing temperature tests on an electronic equipment and I am getting some confusing results. The lowest the ambient temperature, the bigger the delta between the ambient and the equipment case. How is this possible? Is there a law of physics describing this effect?
Thanks a lot

 

[phinds]

You need to be more specific about your setup, and some actual numbers would be informative.

 

[gleem]

Yes, data would be nice. But i don't see the problem. In general it might be what I would expect (within limits). How long after changing the ambient temperature are you measuring the case temperature? The ambient temperature is probably not enough to cool the equipment as quickly as the heat is being produced. Also the case temperature is not as important as the circuit boards. One more point is the equipment cooled with a fan or is it passively cooled by conduction of heat to the case. If it is fan cooled measure the exhaust temperature of the fan that is closer to the circuit board temp.