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04-06-2020
09:45 AM

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04-06-2020
09:45 AM

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

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

Solved! Go to Solution.

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04-06-2020
10:22 AM

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04-06-2020
10:22 AM

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 4

04-06-2020
10:22 AM

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04-06-2020
10:22 AM

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

04-07-2020
03:51 AM

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04-07-2020
03:51 AM

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

04-06-2020
10:25 AM

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04-06-2020
10:25 AM

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.

04-07-2020
02:57 AM

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04-07-2020
02:57 AM

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