TABLE OF CONTENTS Attributes of measurement and control devices require the use of units of measurement to define the physical properties. Units commonly used in such applications are of the English system (such as pound, foot, gallon), the SI system (such as kilogram, meter, liter), or some other unique system peculiar to a particular industry.
The International System of Units (SI, from its French name Syst me International d'Unit s) is a simplified system of measurement developed from the metric units of measurement. It has been adopted almost worldwide. In the United States many large industrial leaders have started using the SI system.
SI units use symbols to abbreviate numbers (Table A-1). Using the preferred form may present a large magnitude; therefore, a more suitable term may be used. For example 1,000,000 pascals is expressed as 1 MPa or one megapascals.
| Prefix | Symbol | Multiplying Factor | |
|---|---|---|---|
| exa | E | 10 18 | 1 000 000 000 000 000 000 |
| peta | P | 10 15 | 1 000 000 000 000 000 |
| tera | T | 10 12 | 1 000 000 000 000 |
| giga | G | 10 9 | 1 000 000 000 |
| mega | M | 10 6 | 1 000 000 |
| kilo | k | 10 3 | 1 000 |
| hecto [*] | h | 10 2 | 100 |
| deca [*] | da | 10 | 10 |
| deci [*] | d | 10 ?1 | 0.1 |
| centi | c | 10 ?2 | 0.01 |
| milli | m | 10 ?3 | 0.001 |
| micro | u | 10 ?6 | 0.000 001 |
| nano | n | 10 ?9 | 0.000 000 001 |
| pico | p | 10 ?12 | 0.000 000 000... |
