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pbreuer1-Visitor
1-Visitor
March 13, 2015
Question

Problem when calculating with units

  • March 13, 2015
  • 8 replies
  • 2982 views

Hello!

I'm a new mathcad-user, and I have some problems with calculation of the displacement of a hydraulic motor.
PTC Mathcad obviously calculates differenz results, when using units and no units ! ????


calculation without units:

q = ( (590,72 * 2 * PI) / 380 * 10^5 * 0,9 ) * 10^6

q = 108.526

calculation with units:

q = ( (590,72N*m * 2 * PI) / 380 * 10^5Pa * 90% ) * 10^6

q = 102.82cm^3

Please help me!

Many thanks in advance!

BR
Paul

8 replies

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
March 13, 2015


Mathcad understands units, and will convert to adjust. I think you converted an old equation that had a unit conversion facor in it.

See attached.

R
RichardJ19-Tanzanite
19-Tanzanite
March 13, 2015

That's certainly not what I see:

This is why it's best to post a worksheet with your question. Without a worksheet it's not possible to say why you are getting the result you see.

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
March 13, 2015

Take the million (unit conversion factor) out of the equation with units, viola!

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RichardJ19-Tanzanite
19-Tanzanite
March 13, 2015

That's not going to yield an answer of 102.82cm^3

P
pbreuer1-VisitorAuthor
1-Visitor
March 16, 2015

Hello Fred!

Hello Richard!

Many many thanks for your prompt and good support.

After checking my worksheet again some hours later I found the mistake.

I defined some variables, two of them had nearly the same name and in my calculation I used the false one!

Sorry for contacting with my greenhorn mistake!

BR

Paul

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