sensor questions

[Tim]

jludwig:
> It takes some time for the temperature sensors to respond and some time for 
> the mass of the heat sink to warm.
> 
> This being the case,  from a "cold" (like say a half hour or more) start, one 
> can get an idea on the accuracy of the temperature sensor(s).

In general, heat sensors are going to be close to the hot device, and
measure the temperature at the point where heat will be a problem.  

Measuring the temperature of a heatsink, itself, is next to useless.
There's no point in having a sensor further along the metal.  Quite
apart from the delays involved in heat transfer, there'd be heat loss,
too (you'd be reading colder temperatures than at the device that's
getting too hot for comfort).

I'd expect sensor readings to react fairly quickly; mere moments, not
minutes.  Of course, they could be too late to react to something
getting too hot to shut it down, that sort of thing is best handled in
another way.  But you should have a useful gauge of whether the device
is cold, warm, hot, or overheating, on average.

You can see the sort of times involved between sensors registering
changes and devices changing temperature if you stop the fan on
something.  Depending on the device, the temperature climbs at a modest,
and predictable rate, with the sensors showing it accordingly.

NB:  Anybody thinking of testing that, do so with care.  Be it on your
own head if you fry your CPU.  I did my testing while everything was
still well under maximum operating temperatures.

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