how to customise unit degree celcius

[bk]

Hello all,

i am using MATHCAD 15,

i want to customise the temperature Default unit (K-Kelvin) in SI to cutomised unit (Degree celcius - oC)

i have tried to convert this using

Tools / worksheeet options / Unit system / Temperature(K) / change unit /in the unit column there is celcius option is given

only "CHANGE DELTA C" is available in need degree celcius

I am new to math cad plaese help me

Regards

Balaji.K

[Werner_E]

Temperature is a tricky and beasty dimension and using °C as "unit" has the drawback, that you would have to use different 'units' for temperature and relative temperature (temp. difference). So there is a reason you are only offered delta°C as an alternative to K and not °C as you might have expected.

The problem with working with temperatures was discussed quite often in this forum in more detail - you may use the search function to access the older postings.

Maybe this blog is of interest to you, too: http://blogs.ptc.com/2012/04/27/temperature-units/

or this: http://www.hearne.co.nz/getattachment/17030b69-68b9-4aca-81bd-f7cba86e43a8/Examples-Tutorials-Working-with-Temperatures.aspx

Here is something to think about:

[AndyWesterman]

Hi.

Your issue seems very strange, when I try to insert a unit I am given the following options:

Perhaps it is something to do with the revision ...

I am using version 15 M010

Does anyone know at what release PTC added the °C function?

Regards

Andy

[Werner_E]

A Westerman wrote:

Hi.

Your issue seems very strange, when I try to insert a unit I am given the following options:

Perhaps it is something to do with the revision ...

I am using version 15 M010

No Andy, Balaji is not trying to simply insert a temp unit but he attempted to change the default temp unit for the sheet. Here (for good reasons) only temp change delta°C is offered but not °C itself.

The problem with Celsius and Fahrenheit scales is their offset from 0.

So when you add temps in degree Celsius all summands but one have to be temp change:

Thats the reason only delta°C can be offered as replacement for Kelvin and not °C.

[AndyWesterman]

Ah, misunderstood.

Absolutely agree - can only make sense working with K or R & then convert the answer into °C

[MJG]

But isn't the only purpose of having a default unit for displaying results? Is it unreasonable to want to display the result in degrees C?

In order to display the result of 50C in Werner's example, he would have had to manually tell it to display C instead of the default K or deltaC.

[Werner_E]

Mark Gase wrote:

But isn't the only purpose of having a default unit for displaying results? Is it unreasonable to want to display the result in degrees C?

Obviously not. Mathcad simply isn't built that way. While "normal" units can be treated as factors this is not true for shifted scales like °C and °F. So Mathcad cheated and implemented those "units" as functions and uses them in a postfix notation. Implemented that way they just can't be used as default unit.