ACCEPTED SOLUTION
Accepted Solutions
One compromise:
ELSID wrote:
Your not quite a diamond member ... YET
Yes you can do what you've done, BUT (i know, I just negated everything before the but), you can no longer use C or F as they are now "re-defined".
The definition in Mathcad of using DT works. As for your re-definition, the built-in DT values are DC=K and DF=(5/9)K and I can continue to use C or F without issues. I cannot emphasize enough that this works with papers, especially to clients and QA/QC staff who may not be as technically competent. They understand D (delta) is a change and the units after is universally accepted.
If this is a petition for PTC to eliminate the DT "unit as it currently stands, I vote to keep the status quo as my pee-wee non- PhD, diamond member, or hero of the month brain understands it clearly!
Maybe you're over thinking it Valery
I often find that educated engineers and good students usually a) know what it is default, which is widely used in engineering, c) know what is temperature and c) have ... sense of humor 
In the book from NIST and ASME (see the cover below) I see only °F but not deltaF in thermal conductivity unit and °R but not deltaF as entropy or (isobaric or isohoric) heat capacity units!
And second and last!
The main topic of this my messege http://communities.ptc.com/docs/DOC-3251
was not "conservative American and British people" but two temperature scale - ITS-68 and ITS-90.
PS
An old joke.
Father and son walking through Paris.
- Dad, who built the tower?
- Engineer Eiffel.
- It's like my mother - an engineer?
- No, my son, your mother is a lead engineer!
Richard Jackson wrote:
I agree with El Sid. I don't see how you can eliminate the deltaT units. The fact is, T and deltaT are different things, and therefore must be represented differently.
K (Kelvin) and °R (Rankin degree) but not delta°C or delta°F.
I have asked one unit expert in NIST (!!!) why in USA you use Btu/(lb °R) for entropy and Btu/(hr ft °F) for thermal conductivity. But in Europe we use kJ/(kg K) and W/(m K). Only in old old books W/(m °C).
This expert replied me that it connected with the "conservatism of the American people"
But what will say about it "the conservative American and British people"?!
And why not (one sheet for Mathcad Mad House - http://communities.ptc.com/groups/mathcad-paradoxes😞
Who am I to "argue" with several PhD's, hero's of the month, and Diamond helpers 
. The notation is funky BUT it works and makes things understandable for most of my audience.
Valery Ochkov wrote:
...Btu/(hr ft °F) for thermal conductivity.
This is a great example of why I use Btu/(hr ft D°F) for thermal conductivity. It "linearizes" the math. I have found that using the "Delta" with the temperature in familiar units is less confussing than switching to Rankin/Kelvin, especially when talking to clients (not always engineers/scientists). In summary, people do not deal in absolute temperature units. It is, however, generally accepted that "Delta" means change the world/clients/laypeople understand °C/°F.
ELSID wrote:
Who am I to "argue" with several PhD's, hero's of the month, and Diamond helpers
Valery Ochkov wrote:
...Btu/(hr ft °F) for thermal conductivity.
This is a great example of why I use Btu/(hr ft D°F) for thermal conductivity. It "linearizes" the math. I have found that using the "Delta" with the temperature in familiar units is less confussing than switching to Rankin/Kelvin, especially when talking to clients (not always engineers/scientists). In summary, people do not deal in absolute temperature units. It is, however, generally accepted that "Delta" means change the world/clients/laypeople understand °C/°F.
From "several PhD's, hero's of the month, and Diamond helpers" to ""conservative American and British people" :
Your not quite a diamond member ... YET
Yes you can do what you've done, BUT (i know, I just negated everything before the but), you can no longer use C or F as they are now "re-defined".
The definition in Mathcad of using DT works. As for your re-defenition, the built-in DT values are DC=K and DF=(5/9)K and I can continue to use C or F without issues. I cannot emphasize enough that this works with papers, especially to clients and QA/QC staff who may not be as technically competant. They understand D (delta) is a change and the units after is universally accepted.
If this is a petition for PTC to eliminate the DT "unit as it currently stands, I vote to keep the status quo as my pee-wee non- PhD, diamond member, or hero of the month brain understands it clearly!
Maybe you're over thinking it Valery 
One compromise:
ELSID wrote:
Your not quite a diamond member ... YET
Yes you can do what you've done, BUT (i know, I just negated everything before the but), you can no longer use C or F as they are now "re-defined".
The definition in Mathcad of using DT works. As for your re-definition, the built-in DT values are DC=K and DF=(5/9)K and I can continue to use C or F without issues. I cannot emphasize enough that this works with papers, especially to clients and QA/QC staff who may not be as technically competent. They understand D (delta) is a change and the units after is universally accepted.
If this is a petition for PTC to eliminate the DT "unit as it currently stands, I vote to keep the status quo as my pee-wee non- PhD, diamond member, or hero of the month brain understands it clearly!
Maybe you're over thinking it Valery
I often find that educated engineers and good students usually a) know what it is default, which is widely used in engineering, c) know what is temperature and c) have ... sense of humor
In the book from NIST and ASME (see the cover below) I see only °F but not deltaF in thermal conductivity unit and °R but not deltaF as entropy or (isobaric or isohoric) heat capacity units!
And second and last!
The main topic of this my messege http://communities.ptc.com/docs/DOC-3251
was not "conservative American and British people" but two temperature scale - ITS-68 and ITS-90.
PS
An old joke.
Father and son walking through Paris.
- Dad, who built the tower?
- Engineer Eiffel.
- It's like my mother - an engineer?
- No, my son, your mother is a lead engineer!
Valery's comparison with lengths and differences in lengths seems invalid to me - lengths and differences in lengths are both the same type of quantity, temperatures and temperature differences are not.
If all lengths were measured relative to a single fixed point in space, so that there would be an "absolute zero" of length, then lengths and length differences would be different
Richard Jackson wrote:
Valery's comparison with lengths and differences in lengths seems invalid to me - lengths and differences in lengths are both the same type of quantity, temperatures and temperature differences are not.
If all lengths were measured relative to a single fixed point in space, so that there would be an "absolute zero" of length, then lengths and length differences would be different
I heard a legend.
The Germans and Swiss have built a bridge across Rhine.
The Germans built a bridge from one side of the river, and the Swiss - on the other.
The bridge converged on the middle of the river with a difference... of 1 m
Why?
Germans have the zero point - the North Sea, and the Swiss - the Mediterranean Sea!
Richard Jackson wrote:
Perfect picture!
This is a bridge for cyclists - no quickly moving and did not go knocking pedestrians
