Cheers

Is there a way to ignore units just for a specific equation?



I have a polynomial approximation of water density table and temperature ϑz in °C. I can ignore units for ϑz variable but then it gets ignored for the rest of the sheet, and it is used very often.
I can create another variable but then I need to define the temperature twice... Is there a workaround?

Thx

It is essential to distinguish variables representing actual physical quantities (number times unit) and just numbers.

It is very common in engineering, that equations are given not as physical equations (which strictly use quantities) but as a package of numerical formula plus specification of what units are to be used in order to generate the input numbers (I refuse to say input quantities) and what unit has to be given to the output number in order to get the result quantity.

Usually, you can do that in a transparent way by just dividing the input quantities by the specified unit and multiplying the output by the desired unit. In the case of temperatures it is more involved, because of the gauge offset. Then you can use an explicit conversion or a conversion function.

If a symbol's value is only meaningful when interpreted using a particular unit, then the name should reflect this fact.



tinc.sm (5 КиБ) скачан 43 раз(а).

I would operate in the way illustrated. However, there are problems with the use of degrees Celsius
sergio

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@mkraska: Thx, that did the trick.

@PompelmoTell: I was trying to do something like that but also had problems with °C because K is default unit. Thx anyway.

Wrote

Is there a way to ignore units just for a specific equation?

Engineering formulas are applied maths, i.e: Unitless as they are developped
in the appropriate system. This is particularly true in Process Control & Instrumentation.
Typical example is the massflow rate [T/hr ... naturally => metric 'Ton'],
as well kg/m³ ... in other word: not compatible SI.
In the empty place holder paste your Engineering Unit.
The attached Water weight density is remarkably accurate up to critical point,
Only in Smath and in my former Mathcad 11 web site [now dead for me from PTC vandalism].



Inst_Water [kg_m3].sm (56 КиБ) скачан 62 раз(а).