CH707013A1

CH707013A1 - Method for qualifying timer to analog display in stop-watch, involves classifying timer in accuracy class among finite number of predefined accuracy classes based on assessment of measurement accuracy of time interval

Info

Publication number: CH707013A1
Application number: CH01751/12A
Authority: CH
Inventors: Guy Semon; Luca Verardo; Nicolas Roland
Original assignee: Lvmh Swiss Mft Sa
Priority date: 2012-09-28
Filing date: 2012-09-28
Publication date: 2014-03-31
Also published as: CH707013B1

Abstract

The method involves measuring, by a timer, an interval of time having a predetermined duration (40), and assessing the accuracy of the measurement (50). The timer is classified (60) in an accuracy class among a finite number of predefined accuracy classes based on the assessment, and the timer is classified (70) in an accuracy category among a finite number of predefined accuracy categories. The timer is classified in the accuracy class by determining a grade of the timer, where the grade is determined according to a highest relative tolerance followed by the timer during the duration. An independent claim is also included for a device for qualifying a timer to an analog display.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention defines a proposal for a standard for measuring the accuracy of the chronometric measurement applicable to mechanical time counters with analogue display.

STATE OF THE PRIOR ART

[0002] A wide range of mechanical time counters with an analogue display is known on the market. The range of quality and precision of time counters varies considerably according to the product ranges. There are counters of very high level, offering very high levels of accuracy. There are also many time counters with comparable, but not identical, levels of accuracy.

The lack of a reference or benchmark for reliably and truly objectively comparing the accuracy levels of the time meters makes it difficult to compare certain important or essential characteristics of the products made available to the users.

[0004] There is therefore a need for a reference or basis of comparison that is objective and controllable in a reliable and repeatable manner.

[0005] In order to overcome these various drawbacks, the invention provides various technical means.

DISCLOSURE OF THE INVENTION

First of all, a first object of the invention consists in providing a test or measurement or qualification method making it possible to verify whether a time counter makes it possible to make an exact chronometric measurement.

Another object of the invention is to provide a test or measurement or qualification method making it possible to check whether a given time counter meets substantially high criteria and quality levels, including the possibility of comparing the Levels of accuracy or accuracy between various time counters. To this end, the invention provides a method for qualification of an analog display time counter comprising the following steps: measuring by the time counter a time interval having a predetermined duration; - evaluation of the accuracy of the measure; - according to this evaluation, classification of the time counter in an accuracy class among a finite number of predefined accuracy classes,

Thanks to such a method, it is possible to classify different time counters strictly and objectively, according to their level of accuracy.

[0009] Advantageously, the classification of the time counter in an accuracy category makes it possible to evaluate for how long the time counter is precise.

Such a classification of the time counter in an accuracy class among a finite number of predefined accuracy classes advantageously comprises the determination of a grade of the time counter.

[0011] Advantageously, the grade is determined as a function of the greater relative tolerance respected by the time counter for the predetermined time.

According to an advantageous embodiment, the method comprises the following steps: starting the time counter, the resolution of which is known, and a reference clock for a predetermined duration; for each passage of a needle Of the time counter to a marker, evaluating an error by comparing the time counter hand with a reference clock hand, determining the largest relative tolerance value selected from a plurality of predefined values For which the error is less than a threshold, the threshold being the greater threshold between the resolution of the counter and the product of the relative tolerance and the time measured between the start of the measurement and the passage of the needle to the reference mark; Stopping the time counter and the reference clock at the end of the duration,Determining the highest relative tolerance within the relative tolerances determined each time the needle passes through the mark, determining the grade based on the highest relative tolerance determined, determining the class of the counter on the basis of grade .

According to yet another advantageous embodiment, the method comprises the following steps: evaluation of the instant when said error is greater than the resolution, classification of the time counter in an accuracy category from among a number Finite predefined accuracy categories based on that instant.

[0014] The invention also provides a chronograph watch qualified by the method as previously described. A chronograph watch qualified by the method according to the invention makes it possible to provide a reliable indication as to the level of accuracy or accuracy achieved or not achieved by the chronograph watch.

[0015] Finally, the invention provides an apparatus for qualification of time counters, comprising: a measuring equipment comprising: a reference clock; An optical system for determining the position of a needle on the dial of a time counter; An electronic system arranged to determine the accuracy of a time measurement performed with the time counter by comparison with a duration measured by the reference clock and to provide a result for classifying the time counter in a class Of accuracy among a finite number of predefined accuracy classes and / or in an accuracy category among a finite number of predefined accuracy categories.

The precision of the chronograph is controlled with reference to a reference time base, such as, for example, a clock calibrated by an analog clock having a precision of the order of magnitude of 10-8 s, or this analogue clock directly or Which is typical of timing errors which are carried out over short periods but with high resolution, for example a resolution at the tenth, the hundredth or the thousandth of a second.

[0017] According to another advantageous embodiment, the precision check is carried out for a predetermined period of time, and a precision margin is also assigned to this determined duration. The test can thus be adapted according to the characteristics of the chronographs to be certified. Moreover, the margin of precision is advantageously established so as to ensure that the certified watches are synonymous with a high level of performance.

In an advantageous variant, the determined duration corresponds substantially to a fraction of the maximum running time of the time counter, for example between 50% and 100% of the maximum running time, advantageously 2/3 of this duration Of maximum walking.

DESCRIPTION OF THE FIGURES

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 and 2, presented solely for the purposes of non-limiting examples, and in which:

FIG. 1 is a functional flow chart showing the main steps of an embodiment of the method according to the invention.

FIG. 2 shows an example of a state, that is to say of the absolute error, as a function of the timing time for a given counter. DETAILED DESCRIPTION OF THE INVENTION Definitions An analog display mechanical time counter is an instrument capable of measuring a time interval by counting a number of periodic events generated by the mechanical oscillator of the system during the duration of this period interval. This number is displayed analogically, ie with the aid of a pointer moving on a dial according to a given incrementation.

The increment corresponds to the duration which separates two periodic events displayed by the counter and defines the resolution R of the counter.

[0022] The time performance can be defined by two parameters: a relative accuracy tolerance Ti required for any measurement of a duration less than or equal to a predetermined duration D, for example equal to 2/3 of the running time Of the meter, starting from initial conditions previously defined. - An accuracy range characterized by the longest timing time, the display of which remains accurate. This characteristic is in relation to the resolution R of the counter

DISTRIBUTION BY CLASSES OF TIME COUNTERS

Relative Accuracy Grade Classes [0023] The time counters are divided into classes according to their accuracy rank. This proposed standard defines the accuracy requirements for a time counter.

The membership of a grade G is defined on the basis of the relative tolerance Ti on the inaccuracy of the time interval measurements. This relative tolerance is expressed as a fraction of the measured duration: a relative tolerance of one thousandth (10 3) corresponds to an absolute tolerance of 1 ms for a duration of one second, 10 ms for a duration of 10 Seconds.

The relative tolerance Ti is always a negative power of 10 (10Λ (-3), 10Λ (-4) etc.). In other words, the relative tolerances Ti are separated by a power 10.

For times where the relative tolerance Ti is translated by an absolute tolerance lower than the resolution of the time counter, it is the resolution R alone which fixes the performance of the counter.

The requirement on the relative tolerance of the meter is maintained for the entire predetermined duration D, for example for 2/3 of its running time. A timekeeper must therefore respect the following requirement for all durations d less than the predetermined duration D, for example 2/3 of its running time: E <max (R, Ti xd) where E is the error of Absolute measurement, R is the resolution of the counter, Ti has a fixed relative tolerance and d indicates any duration less than interval D.

The grade G of a time counter is defined by the greatest relative tolerance Ti respected by the counter over the recorded duration D: G = - Log-io (Ti). [0029] Class 1 is assigned to all Time counter of grade G> 5; Class 2 for a counter G> 4 but less than 5 and so on.

This grade can be numerically determined precisely to give a finer estimate of its quality (4.1 for example, or 4.9).

Accuracy Categories [0031] If the grade G, and hence the class, gives an indication of the accuracy of the meter, the category gives an indication of the time during which the meter respects the level of precision.

The belonging to an accuracy category is defined by the range of accuracy of the counter display. The category is defined by the diurnal error (measured in seconds / day) committed by extrapolating the drift of the counter.

Table 1 below gives an indication of the repair in categories as a function of the diurnal error, independently of the resolution R of the meter. Category error admissible / [s / d] ***** .j 2 **** 24 *** 4.8 ** 9.6 * 19.2

Table 1: Distribution of the fields of accuracy Table 2 below gives an example of a minimum duration calculated for a counter having a resolution of 4 Hz. Category Minimum duration / [s] ***** 9000 **** 4500 *** 2250 ** 1125 * 563

Table 1: Example for a resolution R of 4 Hz.

For example, the drift of 1.2 s / d (σ = 0.000014 Hz) is the permissible limit for the classification in the five-star category (*****) of the accuracy domain. If the meter displays 1/10 of a second (donation has a resolution R of 0.1), an error in displaying the meter must be discernible only after a minimum timing time of: t = R / σ = 7200 s.

The display error will be perceived more or less "early" as a function of the resolution R of the counter. For a counter displaying 1/1 OOs (R = 0.01), the accuracy range required for the same five-star category (*****) is reduced by a factor of 10, ie t = 720s (expressing the same Drift limit of 1.2s / d)

PRINCIPLE OF MEASUREMENT

The principle of the measurement consists in comparing the time displayed by the counter with that of a reference clock (or chrono-comparator).

[0038] Practically, the measurement consists of identifying the exact moment of the transition from the analogue display to certain marks. For a time counter in the form of a chronograph watch, the display generally consists of a needle moving on markers positioned on a dial. This one therefore regularly returns by its point of origin at 12H. The time of passage of the needle is recorded at its point of origin which is compared with a reference clock.

Several methods can be envisaged for detecting the passage of the needle to its origin mark (interception of a laser beam, contrast detector, high-speed camera, etc.).

The internal clock of the measuring equipment must be sufficiently precise to enable the drift of the meter to be determined.

[0041] Two measurements can be made; One in position CH (essentially horizontal) and the other in position 6H (ie substantially vertical). The class and category for each position (eg Class ***, Class 3) is indicated. In a preferred variant of the two classes determined only that one indicating a lower accuracy will be retained. The same considerations apply to categories.

The measurements are preferably carried out according to predefined standard initial conditions, such as, for example, complete barrel wrapping, ambient temperature, synchronization of the reference clock during the first passage of the needle to the marker, fixed position, by Example position CH, duration D fixed.

Example of detailed steps for obtaining the rank of a time counter: [0043] 0. Calibration of the reference clock (belonging to a measuring equipment, which also includes a calculation unit) with the analog clock .

1. Preparation of the predefined initial conditions (complete barrel wrapping, fixed position, ambient temperature, recording time D preferably set equal to 2/3 of the running time or other to be specified, synchronization with reference clock ).

2. Starting the time counter, of which the resolution R is known, and of the reference clock for the duration D.

3. For each passage from the pointer to the mark: evaluation of the error E by comparison (optical or otherwise) of the hand of the time counter with the hand of the reference clock; Of the largest value of Ti for which E <max (R, Ti x time measured between the start of the measurement and the passage from the needle to the mark), by trying with different values of Ti.

4. Stopping the time counter and the reference clock at the end of this duration D.

5. Determination of the greatest relative tolerance Ti among the tolerances Ti determined in point 3.

6. Calculation of the grade G as G = -Log10 (relative tolerance of step 5).

7. Determination of the class of the counter on the basis of G.

Example of detailed steps for determining the category of a time counter: [0051] 0. Calibration of the reference clock (belonging to a measuring equipment, which also includes a calculation unit) with the clock analog.

1. Realization of the predefined initial conditions (complete barrel wrapping, fixed position, ambient temperature, recording time D fixed preferably equal to 2/3 of the running time or other to be specified).

2. Determination of a table "categories vs minimum duration" for the counter under examination, the resolution of which is known R (minimum duration = s × R).

3. Starting the time counter and the reference clock.

4. Evaluation of the difference [error E] between the position of the needle of the time counter and that of the hand of the reference clock (for example by optical comparison) at each passage of the needle At the mark.

5. Evaluation of the time at which this error E is greater than the resolution R.

6. Measurement of the time between the initial instant and that of the previous step.

7. Determination of the category of the counter on the basis of this duration and the table in point 2.

Claims

[0059] FIG. 1 is a functional flow chart showing the main steps of an embodiment of the qualification method according to the invention. In step 10, the reference clock is calibrated. In step 20, the barrel of the time counter is armed, in a calibrated manner, preferably by fully arming it. In step 30, the counter is started: the chronograph of the watch is started in order to be able to perform a time measurement of a determined duration (step 40). The start-up action can be either manual or automated. The actions taken in the qualification are initiated and are carried out in a pre-determined sequence until the end of the measurements at step 40. At step 50 an evaluation of the Accuracy is performed. The following steps relate more directly to the desired objective, namely, in step 60, a classification of the time counter in an accuracy class among a number of predefined accuracy classes, and in step 70 , A classification of the time counter in an accuracy category among a number of predefined accuracy categories. The class and the category are two parameters which can be evaluated independently of each other. However, as discussed, only one (and even) measure can determine both. The watch to be qualified is positioned in a device that is specifically adapted, such as a test chamber, for making measurements inherent in the precision of the mechanism that is the subject of the qualification. Such a device may comprise means for housing one or more watches to be certified and means for measuring or detecting the value or values indicated by the chronograph either at certain given moments, such as for example at the end of the period in question, keep on going. The device optionally comprises elements making it possible to subject the watches of the enclosure to one or more physical constraints. External members may also be in connection with the enclosure, for example in order to deliver hot or cold air thereto. The measurements can therefore be carried out under various conditions deemed representative of the level of quality or precision that the qualification aims to validate. [0063] Various means can be used to carry out the measurements. For example, At least one precision measurement is carried out by means of a high-frequency camera (for example 20,000 images per second) filming at least one of the hands of the chronograph. A processing or analysis of the images makes it possible to associate very precisely the position of the needle filmed with a given value of elapsed time measured by the chronograph. In another example, at least one measurement of precision is carried out by means of a microphone capturing the beats of the movement. The counting of the number of beats makes it possible to deduce the measurement of the time achieved by the chronograph, but does not take into account the possible play in the gears, and is ill-suited to watches comprising several organs whose beats are superimposed. Several measurements of different kinds can be carried out with measuring means of different types. [0064] FIG. 2 illustrates an example of the state and the drift as a function of the timing time of a counter having a fixed resolution. The state is the absolute error with respect to time T, (expressed in s, min, etc.). The drift expresses the slope of the function: variation of the state as a function of time (expressed in Hz, s / d, etc.). The method according to the invention makes it possible to define measurements and conditions in which the measurements are carried out so as to verify in a reliable and realistic manner the level of accuracy of a time counter. The implementation of such a test may be entrusted to a neutral and independent authority, So that the qualification can be applied strictly identical to time counters of various origins. The test can also be applied internally, by a manufacturer, to check specific quality levels. In all these cases, the potential users and acquirers of time counters have a reference tool enabling them to know the level of accuracy of a time counter. claims

1. A method for qualifying an analog display time counter comprising the steps of: measuring by said time counter a time interval having a predetermined duration (D); - evaluation of the accuracy of the measure; - according to said evaluation, classifying said time counter in an accuracy class from a finite number of predefined accuracy classes, and / or classifying said time counter in an accuracy category from a finite number of d categories Accuracy.

2. The method according to claim 1, the classification of said time counter in an accuracy class from a finite number of predefined accuracy classes comprising determining a grade (G) of the time counter.

3. The method according to claim 2, wherein the grade (G) is determined as a function of the greatest relative tolerance (Ti) observed by said time counter during said duration (D).

4. The method as claimed in claim 3, comprising the following steps: starting the time counter, the resolution (R) of which is known, and a reference clock for said duration (D) (TO) evaluating an error (E) by comparing the hand of the time counter with a hand of a reference clock, determining the greatest tolerance value (Ti) selected from a plurality of predefined values for which the error (E) is less than a threshold, said threshold being the largest between the resolution (R) of the counter and the product of the relative tolerance (Ti) and The duration measured between the start of the measurement and the passage of the needle to the reference mark (t0),Stopping the time counter and the reference clock at the end of said period (D), determining the greatest relative tolerance (Ti) among the relative tolerances (Ti) determined each time the needle passes through Determination of grade (G) on the basis of the highest relative tolerance (Ti) determined, - determination of the class of the counter on the basis of grade (G).

5. The method according to claim 4, comprising the following steps: evaluation of the time at which said error (E) is greater than the resolution (R), classification of said time counter in an accuracy category from among Finite number of predefined accuracy categories based on that instant.

6. The method according to claim 1, wherein said time interval (D) is a fraction comprised between 50% and 100% of the maximum running time of said time counter.

7. The method as claimed in one of claims 4 to 6, comprising as a preliminary step the calibration of the reference clock.

8. The method according to claim 1, comprising as a preliminary step the complete wrapping of a barrel of said time counter.

9. The method according to claim 4, comprising synchronizing said reference clock during the first passage of said hand of said time counter at said mark (tO) of said dial.

10. The method according to claim 4, comprising the following steps: assigning class 1 to the time counter if the grade (G) of said time counter is greater than or equal to five; Class 2 to the time counter if the grade (G) of said time counter is less than five and greater than or equal to four; assigning class 3 to the time counter if the grade (G) of said time counter is less than Four and greater than or equal to three, assigning class 4 to the time counter if the grade (G) of said time counter is less than three and greater than or equal to two, assigning class 5 to the time counter if The grade (G) of said time counter is less than two and greater than or equal to one,Assigning class 6 to the time counter if the grade (G) of said time counter is less than one and greater than or equal to zero.

11. The method according to claim 1, comprising determining the class and / or the category of said time counter in two different positions (CH, 6H) of said time counter.

12. A chronograph watch, characterized in that it is qualified by the method according to one of claims 1 to 11.

A time counter qualification apparatus, comprising: measuring equipment comprising: a reference clock; An optical system for determining the position of a needle on the dial of a time counter; An electronic system arranged to determine the accuracy of a time measurement (D) performed with said time counter by comparison with a time measured by said reference clock and to provide a result for classifying said time counter in An accuracy class from a finite number of predefined accuracy classes and / or an accuracy category from a finite number of predefined accuracy categories.