Method for controlling a timepiece

Abstract

The invention relates to a method for controlling a timepiece, the method comprising the steps of: - placing the timepiece in a predetermined relative position with respect to at least one magnetic field source and / or with respect to at least one magnetic field measurement device; - exposing the timepiece to at least one predetermined, time-variable magnetic field; - measuring at least one characteristic of the magnetic field in the vicinity of the timepiece; - inferring a magnetic response of the timepiece from the measured characteristic of the magnetic field; - comparing the magnetic response of the timepiece with a reference magnetic response.

Description

DESCRIPTION TITLE: Method for inspecting a timepiece Technical field of the invention

[0001] The present invention relates generally to methods for inspecting timepieces. In particular, the present invention relates to an inspection method, a measurement method, or an authentication method involving the application of a magnetic field, such as a variable magnetic field, to or through at least one component of the timepiece, for inspecting, measuring, or authenticating said component or the timepiece itself. Prior art

[0002] It is known in the prior art of horology that magnetic fields can disrupt the operation of timepieces (especially watch movements). It is known to measure the resistance or robustness of timepieces to magnetic fields by applying magnetic fields to perform specific tests, called stop tests, as described, for example, in document CH 718 969 A2. However, watchmakers know that exposing timepieces (typically watches) to magnetic fields should be avoided.

[0003] It is known to perform control tests on components by applying a magnetic field. However, due to the interference caused by magnetic fields on the operation of watch parts, as mentioned above, this type of control based on exposure to magnetic fields is not used in the watchmaking industry. Description of the invention

[0004] One object of the present invention is to overcome the drawbacks of the prior art mentioned above and, in particular, first of all, to propose a method of control, or a method of measurement, or a method of authentication, which can be applied to a timepiece without disrupting its operation, in particular without disrupting its operation in a lasting or permanent way, and which allows for the rapid control, measurement or authentication of a component of the timepiece or the timepiece itself.

[0005] To this end, a first aspect of the invention relates to a method for inspecting a timepiece comprising at least one electrically conductive component, the inspection method comprising an inspection phase with the steps consisting of: - to place the timepiece, or at least a part of the timepiece, in a predetermined relative position with respect to at least one source of magnetic field and / or with respect to at least one magnetic field measuring device, - exposing the timepiece, or at least a part of the timepiece, to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - to measure, using at least one magnetic field measuring device, at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field which varies over time, - to deduce a magnetic response of the timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, - compare the magnetic response of the timepiece to a reference magnetic response.

[0006] According to the implementation described above, the control method includes a step of exposing the timepiece to at least one predetermined magnetic field that varies over time. The applicant was surprised to find that such exposure to fields Variable magnetic fields, particularly those of low amplitude, did not disrupt the operation of the timepiece (no stops or malfunctions were observed). Furthermore, measuring at least one characteristic of the magnetic field in the vicinity of the timepiece allows for the deduction of a response from the timepiece that can be compared to a reference magnetic response. This allows for the control, measurement, or authentication of the timepiece, particularly by: - verifying / checking the similarity of the timepiece's response with a reference magnetic response, and / or - measuring the difference between the timepiece's response and the reference magnetic response, - comparing the response of the timepiece with jigs built around the reference magnetic response... Thus, the timepiece can be checked, measured or authenticated quickly, without affecting its operation, and without necessarily having to disassemble it.

[0007] More generally, the invention may relate to a method for inspecting a timepiece comprising at least one electrically conductive component, or a component of the timepiece, the inspection method comprising an inspection phase with the steps of: - place the timepiece, or the component of the timepiece, at a predetermined relative position with respect to at least one source of magnetic field and / or with respect to at least one magnetic field measuring device, - expose the timepiece, or the component of the timepiece, to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - to measure, using at least one magnetic field measuring device, at least one characteristic of the magnetic field at proximity of the timepiece, or of the component of the timepiece, exposed to the predetermined magnetic field which varies over time, - to deduce a magnetic response of the timepiece, or of the timepiece component, from the measured characteristic of the magnetic field in the vicinity of the timepiece, or of the timepiece component, - compare the magnetic response of the timepiece, or component of the timepiece, to a reference magnetic response.

[0008] In particular, the invention may relate to a method for inspecting a component of a timepiece comprising at least one electrically conductive component, the inspection method comprising an inspection phase with the steps of: - to place the timepiece, or at least a part of the timepiece, in a predetermined relative position with respect to at least one source of magnetic field and / or with respect to at least one magnetic field measuring device, - expose the timepiece to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - to measure, using at least one magnetic field measuring device, at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field which varies over time, - to deduce a magnetic response of the timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, or of the component of the timepiece, - compare the magnetic response of the timepiece to a reference magnetic response. In other words, the method allows a component of the timepiece to be controlled, and consequently, the timepiece itself is controlled.

[0009] According to a preferred embodiment, the invention may relate to a method for inspecting a component of a timepiece comprising at least one electrically conductive component, the inspection method comprising an inspection phase with the steps of: - to place the timepiece, or at least a part of the timepiece, in a predetermined relative position with respect to at least one source of magnetic field and / or with respect to at least one magnetic field measuring device, - expose the timepiece to at least one predetermined magnetic field whose frequency varies over time, generated by the magnetic field source, - to measure, simultaneously with exposure to at least one magnetic field and using at least one magnetic field measuring device, at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field which varies over time, - to deduce a magnetic response of the timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, or of the component of the timepiece, - compare the magnetic response of the timepiece to a reference magnetic response. Thus, the timepiece is exposed to a magnetic field whose frequency varies, and the magnetic field is measured during this exposure, while the frequency varies.

[0010] The control method can be defined by the following characteristics, taken individually or in combination.

[0011] According to one embodiment, the step of exposing the timepiece to the predetermined and time-varying magnetic field (and / or the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined and time-varying magnetic field) is carried out on the a timepiece that is inactive or not functioning. In other words, the method may include a step of stopping or allowing the timepiece to stop before performing the step of exposing the timepiece to the magnetic field, and / or the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field, which varies over time. In other words, the invention may relate to a method for testing a non-functional, unpowered, or stopped timepiece (the movement of the timepiece is stopped). According to one embodiment, the timepiece being tested is "inactive" at the time of the test: there is no battery in the timepiece, no current flowing through any electrical or electronic circuit within the timepiece...In any event and according to a preferred embodiment, the timepiece is an assembly of several components, such as for example a complete watch, in working order (but which may nevertheless be stopped or from which the battery has been removed).

[0012] In one embodiment, the timepiece is free of an electrical coil. The timepiece is free of an electronic device. In one embodiment, the timepiece is free of an electronic identification device. In one embodiment, the timepiece is free of a device that emits and / or receives magnetic fields or radio waves. In one embodiment, the timepiece is free of a device for communicating with a device external to the timepiece.

[0013] In one embodiment, the control method includes an initial step of acquiring a control device and the timepiece. In one embodiment, the control device comprises the magnetic field source and the magnetic field measuring device (it being understood that the magnetic field source and the magnetic field measuring device may be separate and form separate devices, or they can be combined into a single device). In other words, the magnetic field source and the measuring device are separate from the timepiece and are not part of it.

[0014] In one embodiment, the inspection method is free from any communication step with the timepiece and / or with a component of the timepiece. In other words, the timepiece is passive during the execution of the inspection method.

[0015] In one embodiment, the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined and time-varying magnetic field is simultaneous with the step of exposing the timepiece to the predetermined and time-varying magnetic field. In particular, the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined and time-varying magnetic field is not the measurement of a signal emitted by a device of the timepiece in response to the step of exposing the timepiece to the predetermined and time-varying magnetic field.In a preferred embodiment, the timepiece is exposed to a predetermined magnetic field whose frequency varies over time, and at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined, time-varying magnetic field is measured simultaneously with the frequency variation over time. Specifically, this measurement is taken to measure the resulting magnetic field generated both by the current in the external emitting coil and by the currents induced in the metallic or conductive components of the timepiece as a function of the frequency of the emitted magnetic field. The method utilizes the effect of the currents induced by the varying magnetic field in the conductive components of the timepiece. in which case, there is no need to power any coil inside the timepiece.

[0016] According to one embodiment, the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field is a step of measuring the field generated by the magnetic field source, modified or altered by the magnetic field generated by the currents induced in the metallic component(s) of the timepiece in response to the exposure. The effect of the induced currents is directly dependent on the exposure and the metallic components of the timepiece, thus providing a signature. This contrasts with an identification method based on communication with a transmitter / receiver (an electronic tag, RFID, NFC, etc.).Placed within a timepiece, the measurement step of this inspection method is not a measurement step of a particular signal emitted by a passive or active electronic component of the timepiece; rather, it is the measurement of the resulting magnetic field, which is modified by the induced currents generated by the exposure of the metallic components to the predetermined, time-varying magnetic field. The step of exposing the timepiece to the predetermined, time-varying magnetic field in this inspection method is not a step of emitting an excitation or control signal to an identification component or device of the timepiece.

[0017] According to one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, at least: - an amplitude, and / or - a frequency, and / or - an orientation, and / or - a spatial gradient, The magnetic field generated by the magnetic field source is modified or variable over time. As seen above, exposing the timepiece to such a time-varying magnetic field is not detrimental to its operation. In a preferred embodiment, the predetermined, time-varying magnetic field has a frequency and a period, and the frequency and period can vary over time during the time step of exposing the timepiece to the magnetic field.

[0018] According to one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range from 10 Hz to 10 7Hz. According to a preferred embodiment, the frequency of the predetermined magnetic field may vary within one or more ranges of values ​​whose limits are between 10 Hz and 10 7 Hz over time during the exposure of the timepiece to the magnetic field.

[0019] According to one embodiment, during the stage of exposing the timepiece to a predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field varies, and in particular a fundamental frequency of the predetermined magnetic field varies within a frequency range from 10 Hz to 10 7 Hz, preferably in a frequency range from 10 2 Hz to 10 7 Hz, preferably in a frequency range from 5.10 2 Hz to 10 7 Hz, preferably in a frequency range from 10 3 Hz to 10 7Hz. According to one embodiment, the fundamental frequency of the magnetic field is at least greater than 10 Hz, at 10 2 Hz, at 5.10 2 Hz, at 10 3 Hz. According to one embodiment, the frequency spectrum of the magnetic field is free of any signal having a frequency below 10 Hz, at 10 2 Hz, at 5.10 2 Hz, at 10 3 Hz.

[0020] According to one embodiment, said timepiece comprises an intermediate component: - arranged between said at least one electrically conductive component and said at least one magnetic field source and / or said at least one magnetic field measuring device, and - having a thickness of at least 1 mm and / or an electrical conductivity of at least 1.10 7S / m (for siemens per meter) and / or a relative magnetic permeability greater than 50 and preferably a thickness of at least 2 mm and / or an electrical conductivity of at least 1.5 x 10 7 S / m and / or a relative magnetic permeability greater than 80, and during the stage of exposure of the timepiece to the predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range from 10 Hz to 10 4 Hz and preferably in a frequency range from 5.10 2 Hz at 5.10 3Hz. The intervening component (of the timepiece) forms a screen or a screen component arranged between said at least one electrically conductive component and said at least one magnetic field source (or the measuring device). According to this embodiment, if the intervening component is "solid" with a significant thickness, greater than 1 mm or with an electrical conductivity of at least 1.10 7 S / m or with a significant magnetic permeability, greater than 50 (i.e. the electrically conductive component targeted by the method is arranged within the timepiece itself, behind the intercalated component), then it is possible to use a magnetic field with a low frequency to ensure that it "passes through" the intercalated component and thus performs a robust and reliable control.

[0021] According to one embodiment, said timepiece comprises an intermediate component: - arranged between said at least one electrically conductive component and said at least one magnetic field source and / or said at least one magnetic field measuring device, and - having a thickness of no more than 2 mm and / or an electrical conductivity of no more than 1.10 7 S / m (for siemens per meter) and / or a permeability relative magnetic less than 50, and preferably a thickness of at most 1 mm or at most 0.5 mm and / or an electrical conductivity of at most 5.10 6 S / m and / or a relative magnetic permeability less than 5, and during the stage of exposing the timepiece to the predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range of 5.10 2 Hz to 10 7 Hz, preferably 10 4 Hz to 10 7Hz. According to this embodiment, if the interlayer component is "thin" (with a small thickness, less than 1 mm or with an electrical conductivity of at most 1.10 7 If the watch has a magnetic permeability of S / m or low (less than 50) or even no magnetic permeability (i.e., the electrically conductive component targeted by the method is located on the surface of the timepiece), then a high-frequency magnetic field can be used to effectively control, measure, or authenticate the electrically conductive component. This way, the remaining components (especially those located further inside the timepiece than the electrically conductive component) will have less interaction with the varying magnetic field, so the control will be "focused" or "primarily performed" on the electrically conductive component of the timepiece targeted by the control method.

[0022] According to one embodiment, during the step of exposing the timepiece to the predetermined and time-varying magnetic field, the amplitude of the predetermined magnetic field is modified over time to obtain a powerful magnetic field, preferably according to a sinusoidal function.

[0023] According to one embodiment, during the step of exposing the timepiece to a predetermined magnetic field that varies over time, the amplitude of the predetermined magnetic field is within a range of values ​​from 0 T to 5.10 1 T and preferably within a value range from 0 T to 6.10 3 T, and preferably in a value range from 0 T to 10 3 T or within a value range from 0 T to 5.10 -4 T, or within a value range from 0 T to 3.10 -4 T, or within a value range from 0 T to 10 4 T.

[0024] In one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, a relative movement is imposed between the timepiece and the magnetic field source. This relative movement allows the timepiece to be exposed to a varying magnetic field, even if the magnetic field source generates a constant or fixed magnetic field.

[0025] According to one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the orientation of the predetermined magnetic field varies by at least 10°, and preferably by at least 30°, relative to an initial orientation of the predetermined magnetic field. It is possible to generate a rotating magnetic field, even over a limited angular sector, for example, less than 360°.

[0026] According to one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the orientation of the predetermined magnetic field varies cyclically, and for example, the orientation of the predetermined magnetic field varies to impose a rotating magnetic field, for example at a frequency of at least 50 revolutions per second, and preferably at least 5 x 10⁻¹². 2 revolutions per second.

[0027] According to one embodiment, the step of exposing the timepiece to the predetermined and time-varying magnetic field includes a step of electrically supplying at least one electrical coil, or even at least two electrical coils simultaneously or with a time offset.

[0028] According to one embodiment, the step of measuring at least one characteristic of the magnetic field in the vicinity of the part watchmaking includes measurement: - of an amplitude and / or orientation of the magnetic field, and / or - of a current induced in a coil, and / or - of a voltage induced in a coil.

[0029] According to one embodiment, the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece is carried out: - by at least one magnetic field sensor, and / or - by at least one electrical coil, called the receiving coil, preferably by at least one coil of the magnetic field source, called the transmitting and receiving coil, used to generate the predetermined magnetic field, which varies over time. The use of a transmitting and receiving coil allows for a simple measuring device with a limited number of components.

[0030] According to one embodiment, the step of deducing the magnetic response of the timepiece includes: - a comparison between a value of a magnetic field characteristic measured without the timepiece, and a value of the magnetic field characteristic measured in the vicinity of the timepiece, and / or - a calculation of the phase shift between the generated magnetic field and a value of the magnetic field characteristic measured in the vicinity of the timepiece, - an analysis phase involving the construction of a Bode plot, and / or a Nyquist plot, and / or a Fourier series decomposition. Placing the timepiece in a varying magnetic field alters the distribution and amplitude of the magnetic field within and around the timepiece. This resulting modified magnetic field is measured and analyzed to deduce the magnetic response of the timepiece.

[0031] According to one embodiment, the control method includes an initial baseline phase with the steps of: - to place a reference timepiece at the predetermined relative position with respect to said at least one magnetic field source and with respect to said at least one magnetic field measuring device, - expose the reference timepiece to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - measure at least one characteristic of the magnetic field in the vicinity of the reference timepiece exposed to the predetermined magnetic field, which varies over time, - to deduce a magnetic response of the reference timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, - record the magnetic response of the reference timepiece.

[0032] In one embodiment, the step of placing the timepiece in a predetermined relative position with respect to at least one magnetic field source and with respect to at least one magnetic field measuring device includes a step of placing the timepiece in a fixture and / or clamping the timepiece in a fixture, and / or mechanically abutting the timepiece against or within a fixture. In another embodiment, the steps of placing the timepiece in a fixture and / or clamping the timepiece in a fixture, and / or mechanically abutting the timepiece against or within a fixture, are carried out with the timepiece in contact or against a positioning portion of said at least one magnetic field source. Thus, the relative position between the timepiece and the magnetic field source and / or the measuring device is reproducible, reliable, and robust.

[0033] In one embodiment, the step of placing the timepiece at a predetermined relative position with respect to at least one magnetic field source and with respect to at least one magnetic field measuring device includes a step of placing the timepiece within 10 mm, preferably within 7 mm, preferably within 5 mm, preferably within 2 mm, preferably within 1 mm, of at least one magnetic field source and / or with respect to at least one magnetic field measuring device, and most preferably, the timepiece is placed in contact with said at least one magnetic field source and / or with said at least one magnetic field measuring device. Thus, the timepiece is well exposed to the magnetic field, and / or is located near the measuring device, which ensures reliable measurements with a good signal-to-noise ratio.

[0034] According to one embodiment, the step of exposing the timepiece to a predetermined and time-varying magnetic field generated by the magnetic field source, and / or the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined and time-varying magnetic field are carried out at least partially simultaneously.

[0035] According to one embodiment, the step of exposing the timepiece to a predetermined and time-varying magnetic field generated by the magnetic field source, and the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined and time-varying magnetic field are carried out over a period of less than 2 minutes, preferably less than 1 minute, preferably less than 10 s, preferably less than 7 s, preferably less than 5 s, preferably less than 3 s.

[0036] According to one embodiment, the step of exposing the timepiece to a predetermined and time-varying magnetic field generated by the magnetic field source includes: - a first control step consisting of exposing a first portion of the timepiece to a first predetermined magnetic field that varies over time, generated by the magnetic field source, - a second control step consisting of exposing a second portion of the timepiece to a second predetermined magnetic field, which varies over time, generated by the magnetic field source. This allows for the control, measurement, and authentication of distinct parts of the same timepiece.

[0037] In one embodiment, the inspection method is a control method implemented after a specific manufacturing operation of the timepiece. It may be necessary to inspect an assembly operation to verify that all components are present and / or arranged in the correct position. Alternatively, a "new" inspection may be performed immediately after manufacturing to record the result for comparison during subsequent maintenance visits to the workshop, even several years later.

[0038] In one embodiment, the control method constitutes a method for authenticating the timepiece, implemented, for example, during or prior to a maintenance operation. In one embodiment, the authentication method includes an initial signature creation phase before delivery, comprising steps, implemented, for example, during a final manufacturing inspection, consisting of: - place the new timepiece in the predetermined relative position with respect to said at least one magnetic field source and with respect to said at least one magnetic field measuring device, - expose the new timepiece to at least one magnetic field predetermined and variable over time generated by the magnetic field source, - measure at least one characteristic of the magnetic field in the vicinity of the new timepiece exposed to the predetermined magnetic field, which varies over time, - to deduce a magnetic response of the new timepiece from the measured characteristic of the magnetic field in the vicinity of the new timepiece, - record the magnetic response of the new timepiece as a reference magnetic response.

[0039] According to one embodiment, the magnetic response of the new timepiece forms a reference signature, and / or the magnetic response of the timepiece to be checked forms a signature of the timepiece.

[0040] According to one embodiment, the control method includes a final phase comprising the steps of: - quantify the difference between the magnetic response of the timepiece and the reference magnetic response, and / or - compare, with a predetermined threshold, the difference between the magnetic response of the timepiece and the reference magnetic response, and / or - qualify the controlled timepiece as a compliant timepiece or an authentic timepiece, in particular if a difference between the magnetic response of the timepiece and the reference magnetic response is less than a predetermined threshold and / or is acceptable.

[0041] According to one embodiment, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, at least: - an amplitude, and / or - a frequency, and / or - an orientation, and / or - a spatial gradient of the magnetic field generated by the magnetic field source exhibits a non-zero time derivative for at least 10 ns, preferably at least 100 ns, preferably at least 1 ps, preferably at least 100 ps, ​​preferably at least 1 ms, preferably at least 1 s, preferably at least 10 s, preferably at least 1 minute. However, it is not excluded to provide time intervals during which the magnetic field does not vary, although preferably the magnetic field varies throughout the exposure to the magnetic field.

[0042] According to one embodiment, the magnetic field source includes at least one magnet, such as a permanent magnet, and the step of exposing the timepiece to at least one predetermined and time-varying magnetic field generated by the magnetic field source includes a step of imposing at least one relative motion between the magnetic field source and the timepiece.

[0043] According to one embodiment, said field includes at least one predetermined and time-varying magnetic field whose amplitude exhibits a sinusoidal, rectangular, triangular, jump, pseudorandom binary sequence (PRBS), and / or multifrequency signal (sum of several sinusoids of different chosen frequencies). It should be noted that the electric current generating the predetermined and time-varying magnetic field also exhibits this sinusoidal, rectangular, etc., temporal waveform. According to one embodiment, the measurement can be made by progressively varying the frequency, for example, a measurement at a first frequency fi for a certain duration (a few periods), a measurement at a second frequency Ï2 for a certain time (a few periods), etc. According to one embodiment, it is possible to plan to make the measurement with a multi-frequency signal (which includes a sinusoid of first frequency fi and amplitude ai, a sinusoid of second frequency Ï2 and amplitude a2, a sinusoid of third frequency fa and amplitude as, etc.) which allows the test to be done quickly, with a single signal which includes the different desired frequencies.

[0044] In one embodiment, exposure to at least one predetermined, time-varying magnetic field is not intended to demagnetize a component or timepiece. In other words, exposure to at least one predetermined, time-varying magnetic field is neither suitable nor intended to demagnetize a component or timepiece. For this purpose, the variable magnetic field has a frequency greater than 10 Hz, preferably greater than 50 Hz, preferably greater than 60 Hz, preferably greater than 80 Hz, preferably greater than 100 Hz, and preferably greater than 1000 Hz. In particular, if the variable magnetic field sweeps or exhibits a range or spectrum of frequencies, then a substantial portion of the range or spectrum of frequencies is greater than 50 Hz, preferably greater than 60 Hz, preferably greater than 80 Hz, preferably greater than 100 Hz, and preferably greater than 1000 Hz.

[0045] According to one embodiment, exposure to at least one predetermined and time-varying magnetic field is not carried out to move or set in motion any component or mechanism of the timepiece. In other words, exposure to at least one predetermined and time-varying magnetic field is neither suitable nor intended to move or set in motion any component or mechanism of the timepiece. In other words, during the test method, and in particular during exposure to at least one predetermined and time-varying magnetic field: - if the components of the timepiece are stationary, then they remain stationary, - if components or mechanisms of the timepiece are mobile or in motion, then they remain mobile or in motion in the same way, without change.

[0046] In one embodiment, exposure to at least one predetermined and time-varying magnetic field is not performed for the purpose of exchanging data with the timepiece. In other words, exposure to at least one predetermined and time-varying magnetic field is neither suitable nor intended for establishing wireless communication with the timepiece's communication components or units.

[0047] In one embodiment, exposure to at least one predetermined and time-varying magnetic field is not performed to charge or transmit energy to the timepiece. In other words, exposure to at least one predetermined and time-varying magnetic field is neither suitable nor intended for wirelessly charging components, organs, or batteries of the timepiece. Description of the figures

[0048] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of embodiment(s) of the invention given by way of non-limiting example(s) and illustrated by the accompanying drawings, in which:

[0049] [fig. 1] schematically represents at a given instant field lines of a variable magnetic field generated by a transmitting coil with a first frequency;

[0050] [fig. 2] schematically represents the field lines of the variable magnetic field generated by the emitting coil, when a timepiece is placed near the emitting coil;

[0051] [fig. 3] schematically represents the field lines of the variable magnetic field generated by the emitting coil with a second frequency, when the timepiece is always placed near the emitting coil;

[0052] [fig. 4] schematically represents the timepiece in figures 2 and 3, including an electrically conductive component;

[0053] [fig. 5] represents the timepiece of figures 2 to 4, installed near a source of magnetic field and a measuring device together forming a first variant of a control device to measure a magnetic response of the timepiece to exposure to a variable magnetic field;

[0054] [fig. 6] represents the timepiece in figures 2 to 5, installed near a second variant of a control device to measure a magnetic response of the timepiece to exposure to a variable magnetic field;

[0055] [fig. 7] represents the timepiece from figures 2 to 6, installed near a third variant of a control device to measure a magnetic response of the timepiece to exposure to a varying magnetic field;

[0056] [fig. 8] generally represents concrete implementation variants of the magnetic field source, to expose the timepiece to a variable magnetic field;

[0057] [fig. 9] represents a graph showing magnetic responses of several watch parts, measured with the control method implemented by the control device in figure 5 for example;

[0058] [fig. 10] represents a graph showing an example of a variable signal that can be used when implementing this control method.

[0059] Detailed description of implementation method(s)

[0060] Figure 1 schematically represents, at a given instant, the field lines of a varying magnetic field generated by a transmitting coil 10 with a first frequency. In the example given, the transmitting coil 10 is static, and the transmitting coil 10 is supplied with a varying electric current. Figure 1 represents the distribution of the field lines at a given instant. In the case shown, the coil is circular with a square cross-section. The model or distribution of the field lines: - is axisymmetric around the vertical axis of the coil in figure 1; - is symmetric with respect to a plane parallel to the upper or lower face of the transmitting coil 10 and which passes through the center of the transmitting coil 10. In the case of Figure 1, and for the rest of the disclosure, Figure 1 represents a transmitting coil 10 alone, but a core or a frame, for example, made of a material with high magnetic permeability (for example, a ferromagnetic material) can be provided to direct or concentrate the magnetic field lines in a particular way.

[0061] Figure 2 schematically represents the field lines of the varying magnetic field generated by the transmitting coil 10 when a timepiece 100 (represented by dashed lines in Figure 2) is placed near the transmitting coil 10. In the example given, and as in the example in Figure 1, the transmitting coil 10 is always stationary, and the transmitting coil 10 is supplied with a varying electric current (typically an alternating current, for example, a sinusoidal or square wave current). Figure 2 shows the distribution of the field lines at a given instant. It can be noted that the timepiece 100 significantly alters the distribution of field lines compared to the case in Figure 1.

[0062] In particular, and with reference to Figure 4, which forms a schematic diagram, the timepiece 100 includes an electrically conductive component 110. The electrically conductive component 110 can be formed by: - all or part of the watch case (the case middle, the back, the lugs... ), - all or part of an internal component of the timepiece, such as a part of the movement, a rotor in the case of an automatic timepiece...

[0063] The electrically conductive component 110 typically comprises at least one metal part, and it may be foreseen that the electrically conductive component 110 may be formed at least in part from an alloy such as steel, stainless steel (for example, according to grade 1.4404 (or AISI 316L), or grade 1.4539 (or AISI 904L)), or brass, or an alloy of copper, titanium, gold, platinum...

[0064] As is well known, a magnetic field, whose amplitude varies over time, induces electrical voltages in any conductive material placed within that field (the electrically conductive component 110 of the timepiece 100). These induced voltages cause the formation of induced current loops, called eddy currents, whose direction is determined by Lenz's law. According to Lenz's law, the direction of the induced current is such that, through its effects, it opposes the cause that produced it. Eddy currents therefore flow in a direction that creates a field opposite to the field that gave rise to them, thus altering the distribution of the magnetic field.

[0065] We can therefore observe in Figure 2 that the magnetic field, generated by the transmitting coil 10 at the first frequency, exhibits field lines that are modified compared to the field lines in Figure 1. In particular, we can note the presence of field lines within the timepiece 100 itself, at a first depth P1 relative to the bottom of the case of the timepiece 100.

[0066] Figure 3 schematically represents the field lines of the variable magnetic field generated by the transmitting coil 10 with a second frequency, when the timepiece 100 (represented in dotted lines) is always placed near the transmitting coil 10.

[0067] In the example given in Figure 3, the transmitting coil 10 is supplied with a variable electric current (an alternating current such as a sinusoidal or square wave current) having a second frequency, and the second frequency is higher than the first frequency used to illustrate Figures 1 and 2.

[0068] By comparing figures 2 and 3, we can note a significant change in the distribution of field lines within the timepiece 100 in figure 3. In particular, we can note in figure 3 field lines at a second depth P2 relative to the bottom of the case of the timepiece 100, the second depth P2 being less than the first depth P1.

[0069] Figure 5 represents the timepiece 100 of Figures 2 to 4, installed near a magnetic field source 21 and a measuring device 23 together forming a first variant of a control device 20 for measuring a magnetic response of the timepiece 100 to exposure to a variable magnetic field.

[0070] Specifically, control device 20 includes: - the magnetic field source 21 formed by an electrical coil which can be described as a transmitting coil, - the measuring device 23 formed by an electrical coil which can be described as a receiving coil - a mounting 25 forming an imprint to receive the watch part 100 without play in order to guarantee a reliable and repeatable relative positioning between the watch part 100 and the magnetic field source 21 and / or the measuring device 23, - optional clamping means 26, here with an articulated arm which presses the timepiece 100 against the magnetic field source 21, - a data acquisition and control system 24, including in particular: • at least one voltage measuring device V, connected to the magnetic field source 21 and / or the measuring device 23, • at least one current measuring device A, connected to the magnetic field source 21 and / or the measuring device 23, • at least one control unit UC (which may include an electronic control unit, a memory unit, a computing unit, a current generator, a voltage generator, internal means for measuring voltage or current, a communication unit ...) connected to the magnetic field source 21 and / or the measuring device 23, the voltage measuring device V, the current measuring device A, • a display device, which can also form a human-machine interface to receive control instructions from an operator.

[0071] The control unit UC is designed to generate and impose an electric current in the magnetic field source 21 so as to expose the timepiece 100 with a time-varying magnetic field whose predetermined magnetic field frequency is within a frequency range from 10 Hz to 10 7 Hz.

[0072] If, for example, the electrically conductive component 110 is arranged on the surface (or near the surface) of the timepiece, it can be predicted that the frequency of the predetermined magnetic field is within a frequency range of 5.10 2 Hz to 10 7 Hz, preferably 10 4 Hz to 10 7 Hz, to get closer to the case illustrated in figure 3.

[0073] If, for example, the electrically conductive component 110 is arranged far from the surface (or close to the center) of the timepiece, it can be predicted that the frequency of the predetermined magnetic field is within a frequency range from 10 Hz to 10 4 Hz and preferably in a frequency range from 5.10 2 Hz at 5.10 3 Hz, to get closer to the case illustrated in figure 2.

[0074] It is also possible to vary the frequency of the predetermined magnetic field, so as to cover a whole range of frequencies within a general frequency range from 10 Hz to 10 7 Hz. Thus, the entire 100-hour timepiece will be checked / measured / authenticated. Typically, a multi-frequency signal can be applied with a current whose time waveform is the sum of sinusoids of different frequencies h, f2, fa, etc., judiciously chosen. Typically, the frequency of the predetermined magnetic field can be varied according to a pseudo-random binary sequence (PRBS).

[0075] As an example, Figure 10 shows a signal that can be used to vary the frequency of a predetermined magnetic field. Figure 10 shows an example of an electric current that can be applied to the magnetic field source 21. In Figure 10, the signal has an amplitude A varying, for example, from 0% to 100% of full scale, and a frequency that varies with time. The amplitude A of the signal in Figure 10 is generally square or pulsed. A multi-frequency signal can be expected, which can be decomposed into a Fourier series, for example.

[0076] In general, the control unit UC is designed to generate and impose an electric current in the magnetic field source 21 so as to expose the timepiece 100 to a time-varying magnetic field whose predetermined magnetic field amplitude is within a range of values ​​from 0 T at 5.101 T and preferably within a value range from 0 T to 6.10 3 T, and preferably within a value range from 0 T to 10 3 T.

[0077] In the case of Figure 5, the magnetic field source 21 and the measuring device 23 are fixed on an electronic board substrate 22. The magnetic field source 21 and the measuring device 23 can be formed with printed circuits on the electronic board substrate 22. For example, turns can be formed or printed directly on the electronic board substrate 22. Circular turns or turns of different shapes can be provided, depending on the geometry of the timepiece 100 and / or the electrically conductive component 110.

[0078] The control device 20 in Figure 5 therefore comprises a fixture 25 receiving and positioning: - on the one hand, the magnetic field source 21, the measuring device 23 and the electronic board substrate 22, On the other hand, the timepiece 100 is held in place by an impression or a counter-mold, ensuring that the relative position between the timepiece 100, the magnetic field source 21, and the measuring device 23 is reliable and repeatable. Clamping means 26 can be provided to press or hold the timepiece 100 in contact with the magnetic field source 21, for example. Thus, there is no air gap between the timepiece 100 and the magnetic field source 21, so that the timepiece 100 is perfectly exposed to the varying magnetic field generated by the magnetic field source 21.

[0079] The mounting 25, clamping means 26, and electronic board substrate 22 can be made from materials that are non-conductive to electricity and / or "transparent" to magnetic fields, i.e., with a magnetic permeability close to 1, and / or materials non-magnetic. It is possible to use a mounting 25, clamping means 26 made of Teflon or plastic for example.

[0080] In the case of Figure 5, the magnetic field source 21 and the measuring device 23 are formed by separate coils. The magnetic field generated at each point in the vicinity of the magnetic field source 21 is variable. According to Faraday's law of electromagnetic induction, if the magnetic flux coupled with a turn or coil (the measuring device 23) varies with time, a voltage is induced across the coil forming the measuring device 23. Consequently, by placing the measuring device 23 in the vicinity of the magnetic field source 21 and the timepiece 100 (the timepiece to be checked / measured / authenticated), an induced voltage is generated by the varying field across the coil of the measuring device 23. This induced voltage can serve as a basis for deducing the magnetic response of the timepiece 100.

[0081] To perform a check on a particular timepiece 100, it is possible to generate with the magnetic field source 21 the same magnetic field varying over time, and it is possible to iteratively measure the induced voltage: - without any 100 watch parts, - with a reference 100 timepiece; - with a 100 watch part to check / measure / authenticate.

[0082] These different induced voltages can be recorded, and we can then plan to compare them: - directly the induced voltage with the reference timepiece 100 and the induced voltage with the timepiece 100 to be tested, - on the one hand the induced voltage without any watch part 100 and the induced voltage with the reference watch part 100 and on the other hand the induced voltage without any watch part 100 and the induced voltage with the watch part 100 to be checked.

[0083] We can also plan to define a frequency response as the ratio between the induced voltage measured across the coil of the measuring device 23 and the voltage applied across the coil of the magnetic field source 21, with no current in the measuring coil.

[0084] Analyzing these transfer functions for the timepiece 100 under test allows the use of mathematical tools. Representations can be created on a Bode or Nyquist plot, which also allows for comparison between measured timepieces. The analysis of non-sinusoidal periodic signals can be performed using Fourier series decomposition.

[0085] Thus, by comparing the induced voltages according to the different options, we can quantify the difference between the magnetic response of the timepiece 100 being tested and the magnetic response of the reference timepiece 100. It is then possible to check / measure / authenticate the timepiece 100 being tested based on the identified difference (we can verify that the difference is below a threshold, we can check for the absence or presence of a particular parameter or shape on the response curve, etc.).

[0086] It can be noted that in the example in Figure 5, the coil of the measuring device 23 is arranged under the coil of the magnetic field source 21. However, other arrangements or locations can be chosen, both for the coil of the measuring device 23 and for the coil of the magnetic field source 21.

[0087] It is also possible to provide several coils for the measuring device 23 and / or several coils for the magnetic field source 21. It is possible to provide for the simultaneous or sequential supply of one or more coils of the magnetic field source 21, and it is possible to provide for the simultaneous or sequential measurement of an induced voltage across the terminals of one or more coils of the measuring device 23.

[0088] Figure 6 shows the timepiece 100 from Figures 2 to 5, installed near a second variant of a control device 20 for measuring the magnetic response of the timepiece 100 to exposure to a varying magnetic field. Specifically, the timepiece 100 is housed within the second variant of the control device 20, and the remainder of the control device 20 (similar to that in Figure 5) is not shown. In the example of the second embodiment in Figure 6, the timepiece 100 will essentially be exposed to field lines passing through it and normal to its case back or crystal.

[0089] In the example of the second embodiment shown in Figure 6, it can be noted that the control device 20 comprises only a single electrical coil, which can be described as a transmitting-receiving coil. Indeed, it is possible to use a single coil, and the measurement of the current and / or voltage can provide the information necessary for control / measurement / authentication.

[0090] In the case of current measurement, one can quantify the amplitudes and / or phase shifts of the current (more precisely, the current intensity) during tests: - without any 100 watch parts, - with a reference 100 timepiece; - with a 100 watch part to check.

[0091] It is possible to do the same with the voltage across the coil of the control device 20.

[0092] Alternatively or in addition, one can consider measuring the impedance of the transmitter-receiver coil of the control device 20. The impedance of a coil is known to be defined in complex notation by: U = Z . I with U the voltage across the coil and I the current flowing through it. It is also worth remembering that any coil can be characterized electrically by a resistance R and by a reactance X (function of the current angular frequency and the inductance L of the coil) forming the complex impedance Z.

[0093] In the presence of electrically conductive material in a timepiece being tested, the field variation and induced currents cause a change in impedance compared to the case without the timepiece. Specifically, the resistance R takes into account the internal Joule losses of the coil as well as the eddy current losses in the timepiece being tested. The inductance L is related to the distribution of the field lines, which are modified by the presence of eddy currents in the timepiece.

[0094] The different quantities are then a function of the frequency f of the varying magnetic field: - resistance: R(f), - inductance: L(f), - reactance: X(f), - magnitude of the impedance: Z(f), - argument of the impedance: cp(f). Depending on the material and dimensions of the timepiece's components, these functions vary. They can therefore be used as a "signature" or "magnetic response" to characterize a timepiece. In some cases, it is advantageous to define functions that include measurements both with and without the timepiece to facilitate mathematical processing and graphical representation.

[0095] Figure 7 shows the timepiece 100 from Figures 2 to 6, installed in a third variant of a control device for measuring the magnetic response of the timepiece 100 to exposure to a varying magnetic field. The rest of the control device (similar to that in Figure 5) is not shown. In the case of the In the third variant, the timepiece 100 will essentially be exposed to field lines crossing it and parallel to its base or its crystal.

[0096] Figure 8 generally represents variants of the implementation of the magnetic field source 21, to expose the timepiece to a variable magnetic field.

[0097] Figure 8, on the left, shows a single-phase system with a single diametral coil 21 A and a ferromagnetic cylinder 29. It is clear that with a single coil 21 A, a variable magnetic field can be generated, typically by supplying the coil 21 A with a variable current, for example, a sinusoidal current, a square wave current, or more generally, a variable alternating current. If the current is alternating and has a period during which the current reverses, the field lines will have an amplitude that varies over each half-period, and their direction will reverse between the first and second half-periods. The field draws power and its direction reverses, but its orientation does not change.

[0098] Figure 8, on the right, shows a three-phase system with three diametrical coils 21A, 21B, 21C. In this case, the three coils 21A, 21B, 21C can be supplied by a three-phase current system with a period T. The magnetic field rotates relative to the coils 21A, 21B, 21C. The amplitude of the field is constant over time. The field rotates at a speed of f revolutions per second. At 1000 Hz, the field then rotates at 1000 revolutions per second.

[0099] With reference to Figures 5, 6, 7, and 8, it is clear that numerous constructions and arrangements are possible both for generating the variable magnetic field and for measuring it once the timepiece 100 is placed near the magnetic field source. These include: - a transmitting coil, arranged at a certain relative position with respect to the timepiece 100, - several transmitting coils, placed at various relative positions with the 100 watch parts - a receiving coil, arranged at a certain relative position with respect to the timepiece 100, - several receiving coils, placed at various relative positions with the timepiece 100, - a transmitting-receiving coil, arranged at a certain relative position with respect to the timepiece 100, - several transmitting-receiving coils, placed at various relative positions with the timepiece 100, - but we can also provide for one or more magnetic field sensors, placed at various relative positions with the timepiece 100. Regarding the aforementioned magnetic field sensor, one can expect a Hall effect sensor, a magnetoresistive sensor, a giant magnetoresistance, a SQUID type magnetometer (“Superconducting Quantum Interference Device >>”). [000100] Alternatively, a relative displacement can be imposed between the timepiece 100 and the magnetic field source 21. In this case, two superimposed transmitting-receiving coils can be used to perform a differential measurement. The two transmitting-receiving coils are powered identically at a given frequency to generate the varying magnetic field and produce induced currents in the timepiece. If the timepiece is moved along the axis of the transmitting-receiving coils, the resistance and reactance of the two transmitting-receiving coils change according to the axial position of the timepiece, taking into account the geometry and material of the timepiece. The measurement of the reactances and / or impedances can then define the magnetic response, which allows the timepiece 100 to be checked, measured, or authenticated. [000101] Figure 9 represents a graph showing the magnetic responses of several timepieces (watch parts), measured using the testing method according to the invention. Figure 9 shows normalized impedance curves, reconstructed after testing eleven timepieces. Each timepiece was exposed to the same magnetic field, which varied over time, with a frequency ranging from 10 Hz to 10 5 Hz, with a control device comprising a single transmitting-receiving coil, the impedance of which was measured simultaneously with exposure to the varying magnetic field of the timepiece. [000102] The timepieces tested were all of the same model, but ten timepieces from family A were found to be compliant, and an eleventh timepiece from family B was found to be non-compliant, despite having an external visual appearance entirely similar to the compliant timepieces. Specifically, the case material of the ten timepieces in family A was a first grade of stainless steel, and the case material of the eleventh timepiece in family B was a second grade of stainless steel. Also, the internal components present in the case of the ten timepieces in family A during the test were compliant, and the internal components present in the case of the eleventh timepiece in family B during the test were non-compliant, i.e., they were made of different materials and / or had some identifiable geometric differences in the timepieces. [000103] It can be noted that Figure 9 shows all the curves of the timepieces in family A in a very close group, whereas the curve of the eleventh timepiece in family B is very different. It appears that the testing method, consisting of exposing a timepiece to a varying magnetic field to measure a magnetic response, can be used to reliably test / measure / authenticate the timepiece. [000104] The timepiece can be a complete watch, a watch head (case and movement) as in Figure 5, but also a sub- watchmaking system such as a movement, a case without a movement inside, a bracelet..., or even a watchmaking component such as a case back, a bezel, an oscillating weight, a balance spring, ... Depending on the implementation, it may be necessary or practical to disassemble part of the watchmaking piece, such as removing the bracelet from the complete watch or removing the case back. Industrial application [000105] A control method according to the present invention, and its manufacture, are capable of industrial application. [000106] It will be understood that various modifications and / or improvements obvious to a person skilled in the art can be made to the different embodiments of the invention described in this description without departing from the scope of the invention.

Claims

DEMANDS

1. A method for inspecting a timepiece comprising at least one electrically conductive component, the inspection method comprising an inspection phase with the steps of: - to place the timepiece, or at least a part of the timepiece, in a predetermined relative position with respect to at least one source of magnetic field and / or with respect to at least one magnetic field measuring device, - exposing the timepiece, or at least a part of the timepiece, to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - to measure, using at least one magnetic field measuring device, at least one characteristic of the magnetic field in the vicinity of the timepiece exposed to the predetermined magnetic field which varies over time, - to deduce a magnetic response of the timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, - compare the magnetic response of the timepiece to a reference magnetic response.

2. A control method according to claim 1, wherein during the step of exposing the timepiece to a predetermined and time-varying magnetic field, at least: - an amplitude, and / or - a frequency, and / or - an orientation, and / or - a spatial gradient of the magnetic field generated by the magnetic field source is modified or variable over time.

3. A control method according to claim 2, wherein, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range from 10 Hz to 10 7 Hz.

4. A control method according to claim 2 or 3, said timepiece comprising an intermediate component: - arranged between said at least one electrically conductive component and said at least one magnetic field source and / or said at least one magnetic field measuring device, and - having a thickness of at least 1 mm and / or an electrical conductivity of at least 1.10 7 S / m and / or a relative magnetic permeability greater than 50 and preferably a thickness of at least 2 mm and / or an electrical conductivity of at least 1.5 x 10 7S / m and / or a relative magnetic permeability greater than 80, in which, during the stage of exposure of the timepiece to the predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range from 10 Hz to 10 4 Hz and preferably in a frequency range from 5.10 2 Hz at 5.10 3 Hz.

5. A control method according to claim 2 or 3, said timepiece comprising an intermediate component: - arranged between said at least one electrically conductive component and said at least one magnetic field source and / or said at least one magnetic field measuring device, and - having a thickness of no more than 2 mm and / or an electrical conductivity of no more than 1.10 7S / m and / or a relative magnetic permeability of less than 50, and preferably a thickness of at most 1 mm or at most 0.5 mm and / or an electrical conductivity of at most 5.10 6 S / m and / or a relative magnetic permeability less than 5, in which, during the stage of exposure of the timepiece to the predetermined and time-varying magnetic field, the frequency of the predetermined magnetic field is within a frequency range from 5.10 2 Hz to 10 7 Hz, preferably 10 4 Hz to 10 7 Hz.

6. A control method according to any one of claims 2 to 5, wherein, during the step of exposing the timepiece to the predetermined and time-varying magnetic field, the amplitude of the predetermined magnetic field is modified over time to obtain a powerful magnetic field, preferably according to a sinusoidal function.

7. A control method according to claim 6, wherein, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the amplitude of the predetermined magnetic field is within a range of 0 T to 5.10 1 T and preferably within a value range from 0 T to 6.10 3 T, and preferably within a value range from 0 T to 10 3 T.

8. A control method according to claim 6 or 7, wherein, during the step of exposing the timepiece to the predetermined and time-varying magnetic field, a relative movement between the timepiece and the magnetic field source is imposed.

9. A control method according to any one of claims 2 to 8, wherein, during the step of exposing the timepiece to the predetermined and time-varying magnetic field, the orientation of the predetermined magnetic field varies by at least 10°, and preferably by at least 30°, relative to an initial orientation of the predetermined magnetic field.

10. A control method according to claim 9, wherein, during the step of exposing the timepiece to a predetermined and time-varying magnetic field, the orientation of the The predetermined magnetic field varies cyclically, and for example the orientation of the predetermined magnetic field varies to impose a rotating magnetic field, for example at a frequency of at least 50 revolutions / second, and preferably at least 5 x 10 2 revolutions per second.

11. Control method according to any one of claims 1 to 10, wherein the step of exposing the timepiece to the predetermined and time-varying magnetic field includes a step of electrically supplying at least one electrical coil, or even at least two electrical coils simultaneously or with a time offset.

12. Control method according to any one of claims 1 to 11, in which the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece includes the measurement: - of an amplitude and / or orientation of the magnetic field, and / or - of a current induced in a coil, and / or - of a voltage induced in a coil.

13. Control method according to any one of claims 1 to 12, in which the step of measuring at least one characteristic of the magnetic field in the vicinity of the timepiece is carried out: - by at least one magnetic field sensor, and / or - by at least one electrical coil called the receiving coil, preferably by at least one coil of the magnetic field source, called the transmitting and receiving coil, used to generate the predetermined magnetic field which varies over time.

14. Control method according to any one of claims 1 to 13, in which the step of deducing the magnetic response of the timepiece includes: - a comparison between a value of a magnetic field characteristic measured without the timepiece, and a value of the magnetic field characteristic measured in the vicinity of the timepiece watchmaking, and / or - a calculation of the phase shift between the generated magnetic field and a value of the magnetic field characteristic measured in the vicinity of the timepiece, - an analysis phase with the construction of a Bode diagram, and / or a Nyquist diagram, and / or a Fourier series decomposition.

15. A control method according to any one of claims 1 to 14, comprising an initial reference-taking phase with the steps of: - to place a reference timepiece at the predetermined relative position with respect to said at least one magnetic field source and with respect to said at least one magnetic field measuring device, - expose the reference timepiece to at least one predetermined and time-varying magnetic field generated by the magnetic field source, - measure at least one characteristic of the magnetic field in the vicinity of the reference timepiece exposed to the predetermined magnetic field, which varies over time, - to deduce a magnetic response of the reference timepiece from the measured characteristic of the magnetic field in the vicinity of the timepiece, - record the magnetic response of the reference timepiece.

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