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SubjectRe: temperature standard - global config option?


On 8 Jun 2001, Bill Pringlemeir wrote:

>
> >>>>> "MHW" == Michael H Warfield <mhw@wittsend.com> writes:
> [snip]
> MHW> Yes, bits are free, sort of... That's why an extra decimal
> MHW> place is "ok". Keeping precision within an order of magnitude
> MHW> of accuracy is within the realm of reasonable. Running out to
> MHW> two decimal places for this particular application is just
> MHW> silly. If it were for calibrated lab equipment, fine. But not
> MHW> for CPU temperatures.
>
> You do introduce some rounding errors if the measurement isn't in
> Celsius or Kelvin. Ie, you must do a conversion because the hardware
> isn't in the desired units. In this case, the extra precision will be
> beneficial.
>


Take for examples the motherboards with temperature sensors on them. At
some point it will display the temperature of the motherboard. This rises
questions: The motherboard will not have the same temeprature in two
distinct points. The temperature will be highere where there are presne
some thermistors or transistors that need cooloing and have a heatsink on
top of them. So, where are the sensors on the motherboard put ? I don't
think that there are a lot of them and then to display the average
temperature. This would be a stupid thing to do. You want to know the
temperature of the motherboard for different resons. If you have a case
that it is sealed by the manufacturer and cannot keep it open to allow the
components to cooldown when things get hot inside or outside (in the
summer), you will have to rely on the motherboard sensors. And if it
happens to have in your computer some graphics card that generates a lot
of heat (like a Voodoo 2, or GeForce without a cooler), a TV tunner,
some of the heat generated will be passed on to the motherboard. And some
motherboard manufacturers insert beetween PCI/ISA slots different
componenents that can be affected by the heat generated by the cards in
the slots. And your confidence in the sensors in the motherboard
disapperas. The only thing you can trust nowadays is the one that messures
the temperature of the CPU (not very accurate). We can talk about accuracy
of temperature measurment when the sensors inside our computer get as good
as those used in a laboratory. Untill then ...


> If you are going your route, you should send error bars with all the
> measurements ;-) Fine, too many decimals leads to a false sense of
> security. However, no one knows the accuracy of any future
> temperature sensors so why not accommodate the possibility. Certainly
> some band gap semis can give a pretty good measurement if you have
> good coupling. If the temperature sensor was built into the CPU, you
> might actually have accuracy!
>

I haven't encountered any CPU with builtin temperature sensors.


> regards,
> Bill Pringlemeir.
>
> This thread keeps going and going and going...

and going, and going ..... and still going .....

>
>
and still going .........



Regards,

/me

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