# Units of Measurement

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## Basic concepts

### Physical quantities

A physical quantity is a property of a physical substance that can be measured (Wiki). Examples of physical quantities are: mass, time, electric current and so on. One should not confuse the concept of physical quantity and the concept of physical (quantity) values. A physical quantity is an abstract concept, and a physical quantity value is the value of concrete phenomenon property. For example, 5 grams is a physical value of the physical quantity mass.

There are fundamental (base) physical quantities called dimensions:

• length
• time
• mass
• temperature
• electric current
• amount of substance
• luminous intensity

They are fundamental because all other quantities can be expressed via them.

### Units of measurement

An unit of measurement is a definite magnitude of a physical quantity (Wiki). One of the main purposes to use units of measurement in a computer program is to convert values of physical quantities from one unit to other ones.

The total list of units, defined in TechEditor, can be found in UNITS tab.

### Unit prefixes

A unit prefix is a specifier that indicates multiplication factor for the unit it precedes. A simple example of a prefix using is the definition of the kilogram unit kg. Here the prefix kilo ‘k’ precedes the unit gram ‘g’. It means that the magnitude of the unit must be multiplied with the value of the prefix, in this case it is 1000.

TechEditor supports many decimal and binary prefixes (see PREFIXES tab).

## How to use units in TechEditor

The rules of conversion:

• A string can contain unit symbols, prefixes, spaces, division operator sign ‘/’ and power operator sign ‘^’
• No multiplication sign allowed in a string (space symbol ‘ ‘ used instead)
• Only one division sign allowed in a string
• A prefix is not separated by spaces with the unit it belongs to
• Different units are separated by spaces (that is spaces used as multiplication operator)

Examples: MPa  N m  m s^2  kN/m

You can use units of measurement in the following document sections:

• application (MathTranslator object)
• diagram (math blocks)
• report (math or formula object)

The following example converts source units of measurement (Pa) to the target (kPa):

var  X: Double;begin
X := MathTranslator.Convert('2550 Pa', 'kPa'); // X=2.550
end;

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