[TRNSYS-users] Betr.: Re: change units in user made components?

[David Bradley]

Henk,
   There are two levels of input / output unit checking in TRNSYS. 
One level is in the Studio interface where the user can change the 
units of parameters and the units of UNCONNECTED inputs in a 
proforma. As soon as the output of a component is connected to the 
input of another, the value of that output is passed to the input 
without any conversion. The Studio tries to help you by preventing 
you from connecting outputs and inputs that have different units. 
With the Studio level of checking, The second level of input / output 
unit checking is in the Fortran code. If two connected components 
have their YCHECK and OCHECK arrays set correctly with the three 
letter codes that indicate the units of the inputs and outputs 
respectively and if the RCHECK() subroutine has been called during 
initialization then the TRNSYS engine

At 04:31 11/15/2007, Henk Stijnen wrote:
>Thanks, Jeff,
>
>Further question: is special care required in selecting the units 
>while creating the proforma?

The short answer is that yes, you should take care to select input 
units that match the output units of connected components or else you 
will have to put an equation in between the two to convert.

>Does TRNsys "see" the unit difference between e.g. output of one 
>component and input of a connected component? Or is it needed to 
>carefully set input units equal to output units while creating the schema?

   There are two levels of input / output unit checking in TRNSYS. 
One level is in the Studio interface where the user can change the 
units of parameters and the units of UNCONNECTED inputs in a 
proforma. As soon as the output of a component is connected to the 
input of another, the value of that output is passed to the input 
without any conversion. The Studio tries to help you by preventing 
you from connecting outputs and inputs that have different units.

   The second level of input / output unit checking is in the Fortran 
code. If two connected components have their YCHECK and OCHECK arrays 
set correctly in the Fortran code with the three letter codes that 
indicate the units of the inputs and outputs respectively and if the 
RCHECK() subroutine has been called during initialization then the 
TRNSYS engine will print warnings to the list file whenever there is 
a mismatch between the output units of one component and the 
connected input units of another. However, again, no automatic 
conversion is performed.
Kind regards,
  David



> >>> "Jeff Thornton" <thornton at tess-inc.com> 14-11-2007 18:07 >>>
><I've created a new component with connected C++ function. The variables
>in my component have their dimensions and units. In standard TRNsys
>components one can freely change the units and computation goes on. In my
>compo it's also possible to change units. However, in my C++ function only
>numbers are input for the variables. How can I detect which units the user
>has selected? Or is it needed to lock the units in the component and how
>can that be done?>
>
>Henk,
>
>The studio lets you change the units for your parameters and non-connected
>inputs as you have pointed out.  However, the parameters and inputs are
>still written to the TRNSYS input file in the units that were originally
>selected by the author - and therefore passed to the model in the desired
>units.  So, in short, it's not necessary to "detect" the units that are
>being provided to your model - they will be provided in the units that you
>dictate when you create the studio proforma.
>
>Jeff
>
>Jeff Thornton
>President - TESS, LLC
>
>2916 Marketplace Drive - Suite 104
>Madison WI 53719 USA
>
>Phone: 608-274-2577
>Fax: 608-278-1475
>E-mail: thornton at tess-inc.com
>Web: www.tess-inc.com
>
>_______________________________________________
>TRNSYS-users mailing list
>TRNSYS-users at engr.wisc.edu
>https://www.cae.wisc.edu/mailman/listinfo/trnsys-users

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Partner                                        Madison, WI 53719
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Fax: (608) 278-1475
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