## [Semediawiki-user] Units for Temperatures

 [Semediawiki-user] Units for Temperatures From: MovGP0 - 2006-07-28 22:34:23 ```Hi, I've currently a lot of discussion about how to use °C (Degree Celsius) and the like for the representation of Temperature-difference. As you may know has every Unit describing Temperature except Kelvin a non-absolute Zero-Point (notice the "Degree" Keyword). That means that every of these units don't represent a factor, but a function. For example the Temperature given in Degree Celsius is defined as: θ = T {θ} = {T} - 273.15 where θ is the Temperature given in Degree Celsius; T is the same Temperature in Kelvin; and {x} is the number-value of x. In another view you can think of Celsius as a function: °C (x) = (273.15 + x) ∙ 1 K Because of this definition 5°C - 2°C is not 3°C, but 3 Kelvin. Therefore we can't define the relative defined units * Degree Celsius * Degree Fahrenheit * Degree Rankine * Degree Delisle * Degree Newton * Degree Réaumur * Degree Rømer and some others like Bel (Decibel), just by defining a factor. Instead we need a factor and a constant for defining Temperatures, and maybe complex formulas for units like Decibel, rather than just a factor. Also I see troubles with componded units like "Ohmmeter" or "Meter per Second" vs. "inch per minute" which are currently not defineable to. Surly you could write dedicated Unit-Parsers for every physical Size like Acceleration, Frequency, Impulse, etc. But it might be more interresting to have a syntax to handle every unit in a generic way. see also: * http://de.wikipedia.org/wiki/Grad_Celsius#Definition (german; Definition of Degree Celsius) * http://en.wikipedia.org/wiki/Temperature_conversion_formulas * http://en.wikipedia.org/wiki/Decibel * http://wiki.ontoworld.org/index.php/Help:Custom_units * http://de.wikipedia.org/wiki/Liste_der_physikalischen_Formelzeichen (german; Overview of the most important physical Sizes) ys, MovGP0 ```

 [Semediawiki-user] Units for Temperatures From: MovGP0 - 2006-07-28 22:34:23 ```Hi, I've currently a lot of discussion about how to use °C (Degree Celsius) and the like for the representation of Temperature-difference. As you may know has every Unit describing Temperature except Kelvin a non-absolute Zero-Point (notice the "Degree" Keyword). That means that every of these units don't represent a factor, but a function. For example the Temperature given in Degree Celsius is defined as: θ = T {θ} = {T} - 273.15 where θ is the Temperature given in Degree Celsius; T is the same Temperature in Kelvin; and {x} is the number-value of x. In another view you can think of Celsius as a function: °C (x) = (273.15 + x) ∙ 1 K Because of this definition 5°C - 2°C is not 3°C, but 3 Kelvin. Therefore we can't define the relative defined units * Degree Celsius * Degree Fahrenheit * Degree Rankine * Degree Delisle * Degree Newton * Degree Réaumur * Degree Rømer and some others like Bel (Decibel), just by defining a factor. Instead we need a factor and a constant for defining Temperatures, and maybe complex formulas for units like Decibel, rather than just a factor. Also I see troubles with componded units like "Ohmmeter" or "Meter per Second" vs. "inch per minute" which are currently not defineable to. Surly you could write dedicated Unit-Parsers for every physical Size like Acceleration, Frequency, Impulse, etc. But it might be more interresting to have a syntax to handle every unit in a generic way. see also: * http://de.wikipedia.org/wiki/Grad_Celsius#Definition (german; Definition of Degree Celsius) * http://en.wikipedia.org/wiki/Temperature_conversion_formulas * http://en.wikipedia.org/wiki/Decibel * http://wiki.ontoworld.org/index.php/Help:Custom_units * http://de.wikipedia.org/wiki/Liste_der_physikalischen_Formelzeichen (german; Overview of the most important physical Sizes) ys, MovGP0 ```
 Re: [Semediawiki-user] Units for Temperatures From: S Page - 2006-07-29 10:13:21 ```MovGP0 wrote: > Instead we > need a factor and a constant for defining Temperatures, and maybe complex > formulas for units like Decibel, rather than just a factor. > Correct. I just checked in an implementation for Type:Temperature. > But it might be more interresting to have a syntax to handle every unit in a generic way. > Interesting, sure. What benefit would implementing this syntax in SMW give? All SMW's type "understanding" does is handle conversions between units. This saves article authors the effort of converting to standard units and has some minor pedagogical value (e.g. a 200 horsepower engine produces 149,140 watts which is why you don't see cars powered by solar cells on their roofs). But I'm not clear what reasoning you can get out of it (despite working on the code ! :-) > Also I see troubles with componded units like "Ohmmeter" or "Meter per > Second" vs. "inch per minute" which are currently not defineable to. You can store values with units for any quantity and retrieve and sort values in a query just by saying the attribute is of Type:Float. With the upcoming custom unit support SMW will additionally be able to convert between m/sec and inches per minute if you tell it one is 2362 of the other. What would you be able to do if SMW offered more? Thanks for your insights, -- =S ```
 Re: [Semediawiki-user] Units for Temperatures From: - 2006-07-29 10:44:29 ```On Sat, Jul 29, 2006 at 12:34:02AM +0200, MovGP0 wrote: > Surly you could write dedicated Unit-Parsers for every physical Size like > Acceleration, Frequency, Impulse, etc. But it might be more interresting to > have a syntax to handle every unit in a generic way. There is a large repository of units and their relations coming with the Unix tool 'units'. Perhaps this might be a starting point. Regards, jens ```