ASNT

examples of conversions to SI units. In SI, the unit of time is the second (s), but hour (h) is recognized for use with SI. For more information, the reader is referred to the information available through national standards organizations and specialized informa- tion compiled by technical organizations (IEEE 1997; Taylor 1995; Taylor 1998; Taylor 2001).

Multipliers In science and engineering, very large or very small numbers with units are expressed by using the SI multipliers, prefixes of 10 3 intervals (Table 6). The multiplier becomes a property of the SI unit. For example, a millimeter (mm) is 0.001 meter (m). The volume unit cubic centimeter (cm 3 ) is 0.01 m 3 or 10 –6 m 3 . Unit submultiples such as the centimeter,

Table 5 Examples of conversions to SI units

Quantity

Measurement in Non-SI Unit

Multiply by

To Get Measurement in SI Unit

2.908 882 × 10 –4 radian (rad)

Angle

minute (min) degree (deg)

1.745 329 × 10 –2

radian (rad)

square inch (in. 2 )

square millimeter (mm 2 )

Area

645

Distance

angstrom (Å)

0.1

nanometer (nm) millimeter (mm)

inch (in.)

25.4

Energy

British thermal unit (BTU)

1.055 4.184 0.293

kilojoule (kJ)

calorie (cal), thermochemical

joule (J) watt (W)

Power

British thermal unit per hour (BTU/h)

Specific heat

British thermal

4.19

kilojoule per kilogram per kelvin (kJ/kg/K)

unit per pound degree fahrenheit (BTU/lbm/°F)

Force

pound force

4.448

newton (N)

Torque (couple)

foot-pound (ft-lb f )

1.36

newton meter (N·m)

Pressure

pound force per square

6.89

kilopascal (kPa)

2 )

inch (lb f /in.

60 –1

Frequency (cycle)

cycle per minute

hertz (Hz)

Illuminance

footcandle (fc)

10.76

lux (lx) lux (lx)

phot (ph)

10 000

candela per square foot (cd/ft 2 ) candela per square inch (cd/in. 2 )

candela per square meter (cd/m 2 )

Luminance

10.76

1.550 003 × 10 –3 candela per square meter (cd/m 2 )

candela per square meter (cd/m 2 ) candela per square meter (cd/m 2 ) candela per square meter (cd/m 2 ) candela per square meter (cd/m 2 )

footlambert (ftl)

3.426

3.183 099 × 10 –3

lambert

nit (nt)

1

stilb (sb) curie (Ci)

10 000

Radioactivity

37

gigabecquerel (GBq)

Ionizing radiation

roentgen (R)

0.258

millicoulomb per kilogram

exposure

(mC/kg)

Mass

pound (lb m )

0.454 0.556

kilogram (kg)

Temperature

degree fahrenheit (°F)

kelvin (K) or degree celsius (°C)

(increment) Temperature (scale) Temperature (scale)

degree fahrenheit (°F) degree fahrenheit (°F)

(°F – 32) ÷ 1.8

degree celsius (°C)

(°F – 32) ÷ 1.8 + 273.15

kelvin (K)

CHAPTER 1

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Part 4