National Measurement Regulations 1999

3.1

sound power level

decibel

dB

In measuring sound power level in decibels, the number of decibels is the number equal to 10 times the logarithm to the base 10 of the ratio of the sound power in the particular case expressed in watts to a reference sound power of
10–12 watts.

3.2

sound pressure level

decibel

dB

In measuring sound pressure level in decibels, the number of decibels is the number equal to 20 times the logarithm to the base 10 of the ratio of the root‑mean‑square sound pressure in the particular case expressed in pascals to a reference sound pressure of
2  10–5 pascals.

3.3

sound intensity level

decibel

dB

In measuring sound intensity level in decibels, the number of decibels is the number equal to 10 times the logarithm to the base 10 of the ratio of the sound intensity in the particular case expressed in watts per square metre to a reference sound intensity of 10–12 watts per square metre.

3.4

area

hectare

ha

104 m2

3.5

energy

electron‑volt

eV

The kinetic energy acquired by an electron in passing through a potential difference of 1 volt in vacuum.

1 eV = 1.602 177 33  10–19 J

3.6

kinematic viscosity

stokes

St

10–4 m2/s

3.7

length

nautical mile

n mile

1852 m

3.8

mass

tonne

t

103 kg

3.9

mass

metric carat

CM or ct

0.2  10–3 kg

3.10

plane angle

degree

º

π /180 rad

3.11

plane angle

minute

′

1/60  π /180 rad

3.12

plane angle

second

″

1/3 600  π /180 rad

3.13

time

day

d

86 400 s

3.14

time

hour

h

3 600 s

3.15

time

minute

min

60 s

3.16

temperature

degree Celsius

ºC

A degree Celsius is equal in magnitude to a kelvin.

t(ºC) = T(K) – 273.15

where:

t(ºC) is the numerical value of temperature in degrees Celsius.

T(K) is the numerical value of temperature in kelvins.

3.17

velocity

knot

kn

1852/3600 m/s

3.18

viscosity

poise

P

10–1 Pa.s

3.19

volume

litre

L or l

10–3 m3