METRICATION ORDINANCE

METRICATION ORDINANCE

LAWS OF HONG KONG

METRICATION ORDINANCE

CHAPTER 214





CHAPTER 214

METRICATION

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

[9 July 1976.]

1. This Ordinance may be cited as the Metrication Ordinance.

2. (1) In this Ordinance, unless the context otherwise requires

'International System of Units' 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' 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 1, 11 and Ill of the First
Schedule and defined, in the case of the base units and
supplementary units, in the fourth column of the said Part 1 or
11, 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' 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.

3. (1) The Governor may, by other 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 Governor 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;

(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.

4. The Governor may, by order published in the Gazette, amend the
First, Second or Third Schedule.

FIRST SCHEDULE [s. 2.1

THE INTERNATIONAL SYSTEM OF
UNITS

PART 1

The SI base units (See Note

Quantity Name Symbol Definition
length metre mthe length of the path travelled by light
in vacuum during a time interval of
1/299 792 458 of a second.
mass kilogram kgthe mass equal to the mass of the inter-
national prototype of the kilogram kept
by
the International Bureau of Weights ana
Measures.
time second sthe duration of 9 192 631 770 periods of
the radiation corresponding to the tran-
sition between the two hyperfine levels of
the ground state of the caesium-133 atom.
electric ampere Athat constant current which if maintained
current 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
newton per metre of length.





Quantity Name Symbol Definition

thermo- kelvin K the fraction 1/273.16 of the ther-

dynamic modynamic temperature of the triple
point
temperature of water.

luminous candela ed the luminous intensity, in a given
intensity direction, of a source that emits
monochromatic radiation of frequency
540x10 hertz and has a radiant
intensity in that direction of 1/683 of a
watt per steradian.

amount of mole mol the amount of substance of a system
which
substance contains as many elementary entities as
there are atoms in 0.012 kilogram of
carbon 12.

Note: When the mole is use, the
elementary entities must be specified and
may be atoms, molecules, ions, electrons.
other particles, or specified groups of
such particles.

PART 11

The SI supplementary units (See Note

Quantity Name Symbol Definition
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 SymbolExpression in
terms
of other SI units

frequency hertz Hz lis
force newton N m kg/s'
pressure stress pascal Pa N ' 'm2
energy, work, quantity joule J N m
of heat
power, radiant flux watt W J/s
quantity of electricity, coulomb c A s
electric charge
electric potential, volt v W/A
potential difference,
electromotive force
capacitance farad F C/V





Quantity Name SymbolExpression in terms
of other SI units

electric resistance ohm 0 V/A
conductance siemens S A/V
magnetic flux weber Wb V S
magnetic flux density tesla T Wb/m'
inductance henry H Wb/A
luminous flux lumen 1m cd sr
illuminance lux Ix cd sr,/m'
radioactivity becquerel Bq 1/s
amount of absorbed gray Gy J/kg
radiation

PART IV

The SI Prefixes (See Note

Factor by which the
unit is multiplied NameSymbol

1018 exa E
1015 peta p
10 tera T
109 giga G
10 mega m
lo, kilo k
102 hecto h
lo, deca da
lo-' deci d
10-2 centi c
10-3 milli m
10-6 micro m
10-9 nano n
10 pico p
10 femto f
10-18 atto a

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 andlor 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.





SECOND SCHEDULE [s. 2.1
NON-SI UNITS IN GENERAL INTERNATIONAL USE

Quantity Name Symbol Value in SI units

time minute min 60s
time hour h 3600s
time day d 86400s
plane angle degree 0 (n/ 180) rad
plane angle minute (7r/ 10 800) rad
plane angle second (n/648 000) rad
area hectare ha 104 MI
volume litre L 10-3 MI
mass tonne t 10' kg
Celsius degree Celsius C See Note 1
temperature
mass per unit tex tex10` kg/m
length
(see Note (2))
length nautical mile 1 852 m
(see Note (international)
speed velocity knot (1 8521/3 600) m/s
(see Note (international)

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 - T where T. = 273.15K by definition.
Celsius temperature is expressed in degrees Celsius (symbol C) unit 'degree Celsius-is equal to the

t

unit 'kelvin' and an interval or a difference of Celsius temperature may also be expressed in degrees
Celsius.

(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.

THIRD SCHEDULE [5. 3.]

VALUES OF NON-METRIC BASIC UNITS EXPRESSED IN TERMS OF SI
BASE UNITS

Quantity Non-metric basic unit Value in SI base unit

length yard 0.914 4 m

mass pound 0.453 592 37 kg
capacity gallon 4.546 09 x 10-3 MI
(see Note ('))
temperaturedegree Fahrenheit51/9 K (see Note
interval

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 'F) and T is the thermodynamic
temperature expressed in kelvins (symbol K).
Originally 48 of 1976. L.N. 189/87. Short title. Interpretation. First Schedule. Second Schedule. Governor may amend Ordinance by order. Third Schedule. Amendment of Schedules. L.N. 189/87. L.N. 189/87. L.N. 189/87.

Originally 48 of 1976. L.N. 189/87. Short title. Interpretation. First Schedule. Second Schedule. Governor may amend Ordinance by order. Third Schedule. Amendment of Schedules. L.N. 189/87. L.N. 189/87. L.N. 189/87.

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