Additional Dimensions for Mathcad Prime 3.0

ValeryOchkov · ‎Oct 22, 2012

I would like to see in Mathcad Prime 3.0 not only Additional Units - see http://communities.ptc.com/message/190702

but also Additional Dimensions (Physical quantities😞

concentration

mg/L, mol/L, mol/kg, p.p.m., p.p.b. etc

specific heat capacity and entropy

kJ/(kg K), Btu/(lb °R) etc

enthalpy

kJ/kg, Btu/lb etc

quantity of information

bit, bite, kB, MB, GB etc

etc

What would you like have more?

HarveyHensley · ‎Oct 22, 2012

Mathcad Help file refers to dimensions as base units, so that is what I assume you mean by dimensions.

The current (Mathcad 15) base units are as follows: current, length, luminous intensity, mass, money, substance, temperature, and time.

All of your suggestions except bit, byte, etc can be expressed in the base units. I see no need to start having base units that are in fact combinations of true base units.

ValeryOchkov · ‎Oct 23, 2012

Now I must use in my steam-gas thermal cycle calculation two Physical quantities - mass of water/steam and mass of gas:

|-User units-------

kJ/kg:=1000J/kg kJ/kg:=1000J/cd

|-User units-------

See for example Fig. 2.19 here http://twt.mpei.ac.ru/ochkov/T-2012/Chapter2-Units.pdf

I have a dream to have 3-7 user dimensions (Physical quantities) in Mathcad - mass of water/steam and mass of gas for example.

ValeryOchkov · ‎Oct 23, 2012

One more simple example - Function of the cylinder volume.

We have TWO Physical quantities(dimensions) - length-diameter and length-high (of the cylinder).

No error message but must be an error:

An Error message:

StuartBruff · ‎Oct 23, 2012

Harvey Hensley wrote:
Mathcad Help file refers to dimensions as base units, so that is what I assume you mean by dimensions..

It's wrong.

The current (Mathcad 15) base units are as follows: current, length, luminous intensity, mass, money, substance, temperature, and time.

No, those are the base quantities under the Mathcad-extended SI system of quantities; the base units are the ampere, metre, candela, kilogram, <money unit>, mole, kelvin and second. (note that money is not part of the SI and the Mathcad help is slightly misleading upon this point).

All of your suggestions except bit, byte, etc can be expressed in the base units. I see no need to start having base units that are in fact combinations of true base units.

The SI also includes the number 1. The coherent SI unit of all dimensionless quantities, or quantities of dimension one, is the number one, since the unit must be the ratio of two identical SI units. The values of all such quantities are simply expressed as numbers, and the unit one is not explicitly shown. bit and byte are dimensionless quantities.

There is an internationally-defined set of metrological terminology, which unfortunately is not as well integrated into common usage as it should be.

A quantity is a measurable item, such as mass, length, time, force, or angle.
A system of quantities is a set of quantities together with a set of non-contradictory equations relating those quantities.
A base quantity is a quantity, chosen by convention, used in a system of quantities to define other quantities.
A derived quantity is quantity, in a system of quantities, defined as a function of base quantities
A dimension (quantity dimension, dimension of a quantity) is the dependence of a given quantity on the base quantities of a system of quantities, represented by the product of the powers of factors corresponding to the base quantities.

In the SI, the base quantities are length, mass, time, electric current, thermodynamic temperature, amount of substance and luminous intensity. All other quantities are derived quantities, including angle, frequency and angular velocity (and money!).

I see no need to start having base units that are in fact combinations of true base units.

I don't think Valery's suggesting that they are introduced as base quantities. I suspect he merely means add them to the built-in list of quantities ...

Stuart

HarveyHensley · ‎Oct 23, 2012

Stuart,

You are right. I should have used "quantities" instead of "units". Still, the quantities being suggested are secondary to the base quantities. Therefore, I don't regard them as a dimension. And in the end, regardless of the terminology, I still see no need for them. Where would the addition end?

StuartBruff · ‎Oct 23, 2012

Harvey Hensley wrote:
Stuart,
You are right. I should have used "quantities" instead of "units". Still, the quantities being suggested are secondary to the base quantities. Therefore, I don't regard them as a dimension. And in the end, regardless of the terminology, I still see no need for them. Where would the addition end?

The addition ends in a several places:

Number 1: PTC use the correct metrological terminology and put a good Help article on the distinction between quantity, dimension and unit.

Number 2: PTC allow a user to add directly within Mathcad a quantity to the "Dimension" list in the "Insert Unit" dialog, such that simplification process can also make use of the user units and that they are embedded within the worksheet to allow ready incorporation of the additional 'known' quantities (together with their units and dimensions) into another user's Mathcad environment.

Number 3: PTC make the unit system smart enough to recognize the SI prefixes.

Number 4: PTC add the IEC 'data' prefixes to the units system. (well, I suppose, it's really 3b ...)

Stuart