Problem when calculating with units

[pbreuer]

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

[Fred_Kohlhepp]

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.

[RichardJ]

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.

[Fred_Kohlhepp]

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

[RichardJ]

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

[Fred_Kohlhepp]

No, it gives 108.526

same as his unitless calculation.

[RichardJ]

Sure. But what Paul is showing is 108.526 in the first example, and 102.82 in the second example. It's easy to see where large scaling factors that are multiples of 10 come from, but they do not explain the difference between the two results.

[Fred_Kohlhepp]

Not sure what the issue is anymore.

[pbreuer]

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