Horological vocabulary — Part 1: Technical and scientific definitions

The 20 definitions apply to time-measuring instruments or to related devices. A table summarizes the values and units of measurement associated with the definitions. Part 2 deals with definitions of technico-commercial terms.

Vocabulaire horloger — Partie 1: Définitions technico-scientifiques

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ISO 6426-1:1982 - Horological vocabulary
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Standards Content (Sample)

International Standard 642611
Horological vocabulary -
Part 1 : Technical and scientific definitions
Vocabulaire horloger - Partie 7 : D&finitions technico-seien tifiques
First edition - 1982-02-01
UDC 681.11 : 001.4
Ref. No. ISO 642611-1982 (E)
Descriptors : clock making, time measuring instruments, vocabulary, definitions, formulas (mathematics).
Price based on 7 pages

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ISO (the international Organization for Standardization) is a worldwide federation of
national Standards institutes (ISO member bodies). The work of developing Inter-
national Standards is carried out through ISO technical committees. Every member
body interested in a subject for which a technical committee has been set up has the
right to be represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council.
Intrnational Standard ISO 6426/1 was developed by Technical Committee
to the member bodies in May 1980.
ISO/TC 114, Horology, and was circulated
lt has been approved by the member bodies of the following countries :
Australia Japan
Czechoslovakia Romania
Egypt, Arab Rep. of Spain
f the fol countries expressed disapproval of the document
The member bodies o lowing
on technical grounds
Germa ny, F.R.
United Kingdom
0 International Organkation for Standardkation, 1982
Printed in Switzerland

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Horological vocabulary -
Part 1 - Technical and scientific definitions
in the dates, taken in this Order, of the end of the interval (hj)
1 Scope and field of application
and the beginning of it (hi).
This part of ISO 6426 defines the principal technical and scien-
NOTE - In a uniform time scale, by applying formula (l), the expres-
tific terms used in the horological industry. These definitions
sion of the duration is given by the relation :
apply to time-measuring instruments or to related devices.
. . .
T = A (tj - ti) (3)
A table summarizing the values and units of measurement
associated with the definitions is given at the end of this part of
or even more simply, if L = 1, that is if the uniform time scale
ISO 6426.
serves as a reference :
NOTE - The definitions of technical and commercial terms will form
Z = tj - ti . . .
the subject of a future International Standard.
In this case, there is a pure and simple identity between h and t
2 Reference
when the indices agree and the unit of duration is the second as
defined in the international System (SI). If, in addition, the in-
ISO 31/ 1, Values and units of space and tirne.
dices are themselves Chosen from a completely ordered whole
and if j > i, then tj > ti and z > 0. The date (hi) is Prior to
(hj) -
3 Definitions
4 state (E) sf an instrument at the instant ti : The dif-
The Order in which the terms are given is a logical Order,
ference at a precise marked instant ti, between the date hi
without any intention of classification and the numbering of the
which it indicates and the reference date Hi
definitions does not indicate any scale of importante.
Ei = hi - Hi . . . (5)
1 time : Undefined medium in which existing objects appear
to develop irreversibly in the changes which they undergo, and
The unit of the state is the second.
in which events and phenomena appear to occur in their suc-
NOTE - If there is direct access to a reference scale of time main-
tained by a Standard clock for the purpose of marking a date H, the
To this medium corresponds a quantity t allowing, over a time
checking of a time-keeping instrument maintaining its own scale of
scale, the chronological Order of events.
time h by comparison with the Standard consists of dating, that is by
simultaneously marking the same event in two scales of time.
2 date (h or H) : In the physical sense, the date of an event,
related to the time scale associated with a time-keeping instru- When a differente in dates is established (h - H)i :
ment, is the mark of the precise instant (IQ) where it appears in
the instrument to be checked has gained in relation to
the completely ordered chronological sequence of the suc-
cessive indications displayed by this instrument. the Standard clock if Ei > 0;
In a uniform time scale, of which the origin has been suitably the instrument to be checked has lost in relation to the
Chosen, the succession of dates h as a function of the con- Standard clock if Ei < 0.
tinually increasing Parameter t may be described by the rela-
tion : 5 instrumental correction (C) : The correction of the date
which should be made algebraically to the hour read as hi to
. . .
h = At - h, (1) obtain the reference hour Hi at the instant tim
NOTE - A represents a factor which relates to the choosen unit. Ci = - Ei = Hi - hi . . .
3 duration (t, z) : The duration zof an intervalof time (hj, hJ, This correction is negative if the instrument gains and positive if
defined in a given time scale, is the differente it loses in relation to the Standard clock.
z hj-hi . . . The unit of instrumental correction is the second.

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rate (M,) 0% an instrument for the duration z od an in- [~&t)l : Limit value of the rate at the instant t, if z
terwal of time marked at the instants $ and li : The ratio of tends towards zero :
the Variation of the state in a duration 7to the value of this
duration. This is a dimensionless quantity. (AE) T
Limit M* = ~, i.e. bfo(t? - ~ Y e w UO)
Iw,= -~
. . v
This is the derivative sf state E(t) in relation to the time r’. From
this is deduced :
In general, the interval of the Observation time is fixed by the
dates I-I; and H,. marked on the instants tj and ti of the reference
uniform time scale. E(t,) - E(tJ = . Ij .
M(JtMt (104
tj - ti > 0, that is the indices increase with the time t.
M,(t) BS a function of the time (continuous or non-continuous,
analytical Or aleatory. . 1 expressed without dimension.
Ej - Ei Ej - Ei
. . .
One has : Mtr _ [.) = ~ = ~
J 1
A C-j - fi)
Hj - Hi
NOTE - d is the symbol of the duration of the day (86 400 s) and 6 is
the symbol of the differential elements in the mathematical sense.
When the observations are made in the reference scale of time,
a=1 and since T = $ - ti, equation 8 is writte n :
E(ti + T) - E(ti)
9 rate in time (ti + z); average speed lr i7r) : The mean of
M, (ti) = . . ” 19)
the Speed during a determined and specified interval sf time 5.
The basic unit is the second per second Ws), but horological
1 li-tr
r /i;-(ti) = ~ M,(t) 6,r . . .
usage requires that the rate be expressed also in seconds per
S ti
day MdL
Bt is conventionally expressed in seconds per day.
The rate is positive if the gain increases or if the loss decreases
and inversely. In general, the rate depends on the time, the in-
stants, and the physical Parameters describing the environment
1 lf z = kd, ,//;.(r.) = &&jii
sf the instrument.
2 I Hcomes from the determination of the Variation in state of a time-
measuring instrument when the law of change in its Speed is known.
l-et PM 1~ ) be the density of probability of the Speed M, (l) established
or known during the interval of time T,. M,W being in the most general
7 particular aates : These correspond to specified observa-
sense a stochastic function at a certain
IOW ergodicity; one tan
tion intervals but retain their expression without dimension. --
therefore write : E < M, >
Conventional units tan be Chosen from the second per day
(s/d) or any other similar unit Ma, s/h, s/min). +cO
r //t = bfo x PM id x 6kf,
: rate per period of the oscillator (z = T)
3 The mea/s Speed (,NT) of the instrument during the time interval T,
is also its rate M,. The rate is derived from the total Observation of the
: rate per second (z = 1 SI
Operation of the time-keeping instrument, while , (/;; results from its in-
rate per minute (z = 1 min)
i&l,in finitesimal analysis; this leads to an increased knowledge of its perfor-
daily rate (z = 1 d)
: rate per year (z = 1 a)
IQ instantaneous rate (m,) : Voluntary use will be made of
the ~nstz~n~~~eaus rate when the mean Speed of an instrument
1 lt should always be borne in mind that only the index 5 sf M in-
is marked on a chrono-comparator in a reference environmental
dicates the interval of time for measuring the rate (MS: 5 = 1s; Amin:
condition r and during a short interval of time. lt is conven-
5 = 1 min; Md: 5 = Id). The unit used does not necessarly specifiy
tionally expressed in seconds per day Nd).
the interval of time during which the measurement of the rate is made.
The unit tan only be changed by a calculation.
NOTE - The Index r indicates all the specific conditions of the environ-
For exampfe :
ment at the time of measurement of the instantaneous rate. Its
presence is descriptive; it therefore has a very varied expression. For
1 s/d = 1/86400 s/s = 1,157 x IO-5
specifies the Position sf the watch (vertical,
exampk q h, 30 “c
1 s/a = 1/31 556925,9747s/s = 1/86400 x 365,242198781 s/s
6 hours upwards) and the temperature of Observation (30 W.
= 3,169 x IO-8 s/s
In another example, “li indicates the value of the instantaneous rate
marked at the beginning sf thejTh sequence sf a chronological succes-
2 The daily rate Md is the rate of the instrument for the duration sf
sion of observations where the environmental conditions are indexed
one day (r = Id). Its only other indication is M. Its conventional unit is
the second per day (s/d).

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ISO 6426/1-1982 (El
Generally, the drift depends on the time, the instants and the
11 probable rate; probable daily rate ( A$,) : By means of a
functional F of the instantaneous rate obierved in specified Parameters describing the environment of the
environmental conditions reflecting conditions of normal use of
13 particular drifts : These correspond to specified observa-
the instrument during a duration z, the rate which the time-
keeping instrument would probably have if it were placed or tion intervals. Conventional units tan be Chosen from the se-
cond per day squared (s/d*) or the second per day-year [s/(d*a)l.
used during an equivalent interval of time in real conditions
similar to normal use is defined by mathematical or physical
D, = l- [Mo& + z) - MJQ] . . .
For example :
Dd : daily drift (z = ld)
dd& = F [mro(tFJ or F (mj, . . . (12)
D, : annual drift (z = Ia)
when reference is made to the Observation of the instantaneous
rate or when the environmental conditions Change, represent-
NOTE - It should always be borne in mind that only the index z of D
ing the interval z or during a succession of specified configura-
indicates the interval of time for the measurement of the drift.
tions of level j.
The unit used does not necessarily specify the interval of time during
which the measurement of the drift is carried out. Any Change in the
When the interval of time Chosen to express the probable rate is
unit must be made by a calculation.
the day, and the specified environmental conditions corre-
spond to it in their totality, (z = 1 d), one has the probable
14 deviation (DJ : Limit value of the drift at the instant t if z
: APd, also marked as AP for s

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