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DPJB1-Visitor
1-Visitor
April 6, 2020
Solved

Calculation result with and without units is different (bug?)

  • April 6, 2020
  • 4 replies
  • 2068 views

Hello,

 

I found a wired behaviour using units in calculations. The result is slightly different if units are used in formula or not. See attached file. Both results must be identical, but they are not. I can even do the calculation in my head and the one with unit is false.

 

Cheers DPJB

Best answer by LucMeekes

Not a bug.Temperature units are weird.

Realize that 0 °C = 273.15 K.

So without units you are multiplying with 0^3=0 in the last term when t=0.

But when t=0 °C, you are multiplying with (273.15 K)^3.

You should define your constants A, B and C with K, or Delta°C, but not with °C. And you should adapt your formula to include a reference temperature, is that 0 °C ?

 

Success!
Luc

4 replies

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
April 6, 2020

Not a bug.Temperature units are weird.

Realize that 0 °C = 273.15 K.

So without units you are multiplying with 0^3=0 in the last term when t=0.

But when t=0 °C, you are multiplying with (273.15 K)^3.

You should define your constants A, B and C with K, or Delta°C, but not with °C. And you should adapt your formula to include a reference temperature, is that 0 °C ?

 

Success!
Luc

    D
    DPJB1-VisitorAuthor
    1-Visitor
    April 7, 2020

    Thanks for your reply. Makes sense now, not quite intuitive.

    W
    Werner_E25-Diamond I
    25-Diamond I
    April 6, 2020

    The "units" for temperature can be quite confusing.

    Keep in mind, that behind the scenes Prime only uses the base unit Kelvin!

    °C is not a unit you can cancel because its not just a multiplication factor.

    Werner_E_0-1586183225035.png

     

     

      V
      ValeryOchkov24-Ruby IV
      24-Ruby IV
      April 7, 2020

      I wish everyone to have a body temperature 615 cpm and not get sick!

      pv.png

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