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Offline fred47  
#1 Posted : 06 August 2016 02:19:36(UTC)
fred47

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Hi,

I have run into a problem with using units which are reciprocals - specifically Ohms and Siemens.

If I try to add a quantity with units Ohms to the reciprocal of a quantity with units Siemens, an error occurs: Units don't match.

Due to computer limitations where I am presently, I have only text entry.

Example:

Ra := 1 Ohm
Ga := 1 S
Rsum := Ra + 1/Ga = "units don't match"

But they do cancel:

Rprod := Ra * Ga = 1

Is there a work-around I'm missing somehow?

Thanks,
Fred

Edited by moderator 06 August 2016 16:26:53(UTC)  | Reason: Not specified

Offline Davide Carpi  
#2 Posted : 06 August 2016 16:20:10(UTC)
Davide Carpi


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Hello Fred,

it is a bug; as workaround you can transit through a 3rd variable with symbolic optimization on his definition, then it is possible to evaluate numerically this variable in a separate region (see the cloud example)

2016-08-06 15_21_29-SMath Studio Desktop - [OhmSiemens.sm_].png

Edited by user 06 August 2016 16:22:01(UTC)  | Reason: Not specified

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Offline nierges  
#3 Posted : 18 August 2016 11:45:41(UTC)
nierges

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Germany

Hi,

I was trying to implement a formula to calculate needed inductance on a flyback transformer and the program reports that units do not match. However splitting the formula in smaller pieces I was able to get the result out of it.
units dont match.sm (35kb) downloaded 29 time(s).

Thank you.
Offline Davide Carpi  
#4 Posted : 18 August 2016 11:53:04(UTC)
Davide Carpi


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It is the same bug as the one shown in the first post, so I moved your post here.

The problem is related to the numeric evaluation, but there is a workaround:
- remove the RHS (the evaluation = and all after it)
- change optimization to symbolical
- show the result alone (Lp=#)


Bug reported as SS-2368

Edited by user 19 August 2016 18:08:50(UTC)  | Reason: marked as FIXED

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thanks 1 user thanked Davide Carpi for this useful post.
on 19/08/2016(UTC)
Offline nierges  
#5 Posted : 19 August 2016 11:11:59(UTC)
nierges

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Germany

Originally Posted by: Davide Carpi Go to Quoted Post
It is the same bug as the one shown in the first post, so I moved your post here.

The problem is related to the numeric evaluation, but there is a workaround:
- remove the RHS (the evaluation = and all after it)
- change optimization to symbolical
- show the result alone (Lp=#)


Bug reported as SS-2368


Thank you Davide, seems to work following your advice.
Emil
Offline Andrey Ivashov  
#6 Posted : 19 August 2016 18:07:49(UTC)
Andrey Ivashov


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Both issues fixed. See latest available nightly build: http://en.smath.info/for...073--19-August-2016.aspx
thanks 1 user thanked Andrey Ivashov for this useful post.
on 20/08/2016(UTC)
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