On 2/1/2017 3:36 PM, druck wrote:
> On 31/01/2017 23:03, rickman wrote:
>> There would appear to be something wrong with your numbers.  If you
>> raise the ambient temperature 1 degree, the core of the CPU should rise
>> 1 degree.  If you lower the ambient temperature 1 degree, the core of
>> the CPU should lower 1 degree.
>
> Only if there is a perfect heat transfer between the chip's core and the
> surrounding environment.

I'm not sure what *you* mean by "perfect heat transfer", but I can
assure you, all heat created in the CPU is transferred to the environment.


>> Your first example is close enough it can be chalked up to measurement
>> uncertainty (electronic thermometers are not very accurate).  The second
>> example is hard to explain.  I suppose there could be some effect from
>> the air being dryer at temps below freezing and so not being as
>> effective at carrying away the heat.
>
> I suspect its the difference between the active cooling in the fridge,
> and the passive cooling inside the car. The Pi had no heatsink and was
> in a case, albeit one with quite a lot of ventilation, but probably
> enough to retain some heat. All the other temperature sensors were some
> distance away from the case.
>
> What I'll do if I try it again, is to put one of the probes inside the
> case to see how the chip, ambient and case temperatures are related.

At this point I'm not sure what you are doing.  If you want to compare
two things, you need to keep everything else constant.

--

Rick C

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