Messages in this thread | | | Date | Tue, 22 Jan 2008 20:22:07 -0800 | From | "H. Peter Anvin" <> | Subject | Re: W1: w1_slave units, standardize 1C or .001C? Break API |
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David Fries wrote: > On Mon, Jan 21, 2008 at 07:11:07PM -0800, H. Peter Anvin wrote: >> H. Peter Anvin wrote: >>> Millikelvins would have the nice property of never being negative. :) > > True, but the sensor returns the value as a signed integer in C. That > is where the earlier negative number problem was, it would have to do > yet another conversion to go to Kelvin, and it would be just one more > potential for error. Everyone knows that a bad conversion doomed at > least one space craft, let's stick to Centigrade. >
Uhm... the conversion is exact as long as you have at least centikelvin precision (0 °C = 273.15 K by definition, and the multiplier is 1.)
>> Alternatively, centikelvins would fit nicely in 16 bits if anyone cares... >> >> 655.35 K = 382.20 °C = 719.96 °F > > The range for the sensor is -55 to 125 C, if an application didn't > care about precision they could store it in a signed 8 bit value just > fine.
This was more a comment as to it possibly being a convenient format for more than this particular sensor.
The nice thing with kelvins is no need to worry about negative numbers and something misparsing them, that's all.
I certainly did not imply that we should even consider use °F. That's obviously ridiculous.
-hpa
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