Metrication Ordinance


Published: 1997-06-30

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Cap 214 - METRICATION ORDINANCE 1

Chapter: 214 METRICATION ORDINANCE Gazette Number Version Date

Long title 30/06/1997


To provide for the replacement in enactments of non-metric units by metric units and for matters connected therewith.


[9 July 1976]

(Originally 48 of 1976)

Section: 1 Short title 30/06/1997


This Ordinance may be cited as the Metrication Ordinance.

Section: 2 Interpretation 30/06/1997


(1) In this Ordinance, unless the context otherwise requires-
"International System of Units" (國際單位制) means the system of units of measurement from time to time

recommended for international use by the General Conference of Weights and Measures;
"metric units" (十進制單位) means-

(a) the base units, supplementary units, derived units and symbols of the International System of Units
specified in the second and third columns of Parts I, II and III of the First Schedule and defined, in the
case of the base units and supplementary units, in the fourth column of the said Part I or II, as the case
may be, opposite each such unit;

(b) any other units of measurement belonging to the International System of Units;
(c) such decimal multiples and sub-multiples of the metric units referred to in paragraphs (a) and (b) as

may be formed by the use of the prefixes of the International System of Units specified in the second
and third columns of Part IV of the First Schedule and determined, in respect of any particular decimal
multiple or sub-multiple of a metric unit by reference to the factor, specified in the first column of that
Part, by which such metric unit is multiplied;

(d) the units of measurement in general international use, but not belonging to the International System of
Units, which are specified in the second column of the Second Schedule, the respective equivalent
values whereof, expressed in SI units, being specified or referred to in the fourth column of that
Schedule;

"non-metric units" (非十進制單位) means all units of measurement other than metric units.
(2) In this and in any other Ordinance, unless the context otherwise requires-

(a) the abbreviation SI stands for the International System of Units; and
(b) each of the symbols in the third column of the First and Second Schedules stands for the unit or prefix

opposite thereto in the second column.

Section: 3 Chief Executive may amend Ordinance by order 65 of 2000 01/07/1997


Remarks:
Adaptation amendments retroactively made - see 65 of 2000 s. 3


(1) The Chief Executive may, by order published in the Gazette, amend any Ordinance for the purpose of
replacing references therein to non-metric units by references to metric units which are either equivalent or
approximate thereto or which enable the references to non-metric units to be expressed in convenient metric terms.

(2) In any order made under subsection (1) the Chief Executive may, for the purposes of the Ordinance
amended thereby-

(a) prohibit the use of non-metric units after a date specified in the order;
(b) declare the extent to which, and the period during which, non-metric units may continue to be used;
(c) provide for exemptions from the use of metric units for such periods and on such conditions as he may

specify;



Cap 214 - METRICATION ORDINANCE 2

(d) generally make such incidental provisions as he thinks expedient to achieve the purposes of this
Ordinance.

(3) For the purposes of subsection (1), the non-metric base units set out in the second column of the Third
Schedule shall be equivalent to the values expressed in SI base units set out in the third column thereof.

(Amended 65 of 2000 s. 3)

Section: 4 Amendment of Schedules 65 of 2000 01/07/1997


Remarks:
Adaptation amendments retroactively made - see 65 of 2000 s. 3


The Chief Executive may, by order published in the Gazette, amend the First, Second or Third Schedule.
(Amended 65 of 2000 s. 3)


Schedule: 1 THE INTERNATIONAL SYSTEM OF UNITS 30/06/1997


[section 2]


PART I


The SI base units (See Note (1))


Quantity Name Symbol Definition
length metre m the length of the path travelled by light in vacuum during a

time interval of 1/299792458 of a second. (Amended L.N.
189 of 1987)

mass kilogram kg the mass equal to the mass of the international prototype of the
kilogram kept by the International Bureau of Weights and
Measures.

time second s the duration of 9192631770 periods of the radiation
corresponding to the transition between the two hyperfine
levels of the ground state of the caesium-133 atom.

electric current ampere A that constant current which if maintained in two straight
parallel conductors of infinite length, of negligible circular
cross section, and placed 1 metre apart in vacuum, would
produce between these conductors a force equal to 2 x 10-7

newton per metre of length.
thermo-dynamic
temperature

kelvin K the fraction 1/273.16 of the thermodynamic temperature of the
triple point of water.

luminous
intensity

candela cd the luminous intensity, in a given direction, of a source that
emits monochromatic radiation of frequency 540 x 1012 hertz
and has a radiant intensity in that direction of 1/683 of a watt
per steradian. (Amended L.N. 189 of 1987)

amount of
substance

mole mol the amount of substance of a system which contains as many
elementary entities as there are atoms in 0.012 kilogram of
carbon 12.
Note: When the mole is used, the elementary entities must be
specified and may be atoms, molecules, ions, electrons, other
particles, or specified groups of such particles.


PART II


The SI supplementary units (See Note (2))


Quantity Name Symbol Definition



Cap 214 - METRICATION ORDINANCE 3

Plane angle radian rad the plane angle between two radii of a circle which cut off on
the circumference an arc equal in length to the radius.

solid angle steradian sr the solid angle which, having its vertex in the centre of a
sphere, cuts off an area of the surface of the sphere equal to
that of a square with sides of length equal to the radius of the
sphere.


PART III


SI derived units having special names and symbols

(See Notes (3) & (4))



Quantity


Name


Symbol

Expression in terms
of other SI units

frequency hertz Hz 1/s
force newton N m kg/s2
pressure stress pascal Pa N/m2
energy, work, quantity of heat joule J N m
power, radiant flux watt W J/s
quantity of electricity, electric
charge

coulomb C A s

electric potential, potential difference,
electromotive force

volt V W/A

capacitance farad F C/V
electric resistance ohm Ω V/A
conductance siemens S A/V
magnetic flux weber Wb V s
magnetic flux density tesla T Wb/m2
inductance henry H Wb/A
luminous flux lumen lm cd sr
illuminance lux lx cd sr/m2
radioactivity becquerel Bq l/s
amount of absorbed radiation gray Gy J/kg


PART IV


The SI Prefixes (See Note (5))

Factor by which the unit is multiplied Name Symbol

1018 exa E
1015 peta P
1012 tera T
109 giga G
106 mega M
103 kilo k
102 hecto h
101 deca da
10-1 deci d
10-2 centi c
10-3 milli m
10-6 micro μ
10-9 nano n
10-12 pico p
10-15 femto f
10-18 atto a



Cap 214 - METRICATION ORDINANCE 4


Notes


(1) An SI base unit is a unit recommended by the General Conference of Weights and Measures as a fundamental

unit of SI. By convention the seven SI base units are regarded as dimensionally independent.
(2) An SI supplementary unit is a unit for the time being not classified by the General Conference of Weights and

Measures as either an SI base or an SI derived unit.
(3) An SI derived unit is a unit which can be expressed algebraically in terms of the SI base units and/or the SI

supplementary units.
(4) The derived units in Part III have been given special names and symbols which may themselves be used to

express other derived units.
(5) The SI prefixes are used to form names and symbols of decimal multiples and submultiples of the SI units.

Schedule: 2 NON-SI UNITS IN GENERAL INTERNATIONAL USE 30/06/1997


[section 2]


Quantity Name Symbol Value in SI units
time minute min 60 s
time hour h 3600 s
time day d 86400 s
plane angle degree 。 (π/180) rad
plane angle minute ’ (π/10800) rad
plane angle second ” (π/648000) rad
area hectare ha 104 m2
volume litre L 10-3 m3
mass tonne t 103 kg
Celsius temperature degree Celsius ℃ See Note (1)

mass per unit length
(see Note (2))

tex tex 10-6 kg/m

length
(see Note (3))

nautical mile
(international)

1852 m

speed velocity
(see Note (3))

knot
(international)

(1852/3600) m/s


Notes


(1) In addition to the thermodynamic temperature (symbol T), expressed in kelvins, use is also made of Celsius

temperature (symbol t) defined by the equation t = T - T0 where T0 = 273.15 K by definition. Celsius
temperature is expressed in degrees Celsius (symbol ℃). The unit "degree Celsius" is equal to the unit "kelvin"
and an interval or a difference of Celsius temperature may also be expressed in degrees Celsius. (Amended L.N.
386 of 1993)

(2) This unit is used in the textile industry for the measurement of the linear density of yarn.
(3) Related to nautical and aeronautical navigation and meteorology. One knot is equal to one nautical mile per

hour.
(Amended L.N. 189 of 1987)


Schedule: 3 VALUES OF NON-METRIC BASIC UNITS

EXPRESSED IN TERMS OF SI BASE UNITS
30/06/1997



[section 3]


Quantity Non-metric basic unit Value in SI base unit
length yard 0.9144 m



Cap 214 - METRICATION ORDINANCE 5

mass pound 0.45359237 kg
capacity gallon 4.54609 x 10-3 m3

(see Note (1))
temperature interval degree Fahrenheit 5/9 K (see Note (2))


Notes


(1) Correct to 6 significant figures.
(2) A formal definition of the Fahrenheit scale of temperature is not thought to exist, but for most practical purposes

Fahrenheit temperature may be defined by the equation f = 1.8 T - 459.67 where f is the Fahrenheit temperature
expressed in degrees Fahrenheit (symbol oF) and T is the thermodynamic temperature expressed in kelvins
(symbol K).

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