EP0938034A1 - Non-sonic alarm device - Google Patents

Abstract

Alarm comprises a vibrating mass connected to a coil (L) so that it can be made to oscillate. A means for measuring the instantaneous vibration frequency is available as well as a means for applying a series of excitation impulses to the coil the characteristics of which are dependent upon the measured frequency.

Description

The present invention relates to a device non-audible alarm, intended to equip a unit brought to the body contact, such as a watch, cell phone or a pager.

In many situations it is useful to ability to transmit information to a person other than by audio or visual means. It's the especially when you want to prevent so discreet a person who is in the middle of a Assembly.

Tactile means of information transmission offer an interesting alternative for this: is to vibrate a unit that the person wears close to the body, such as a watch for example, so to locally stimulate its epidermis to indicate a given time or the occurrence of an event (arrival of a message, a call, an appointment, etc.)

Vibration type devices unbalance mounted on a rotor are known to the man of the job. In these devices, typically, the unbalance rotates at a speed of a few tens of revolutions per second thanks to an electric motor powered with a power of a few tens of milliwatts and switched on at the moment when the message must be perceived by the carrier.

These devices have the disadvantage main to consume a lot of energy, which is little compatible with battery miniaturization requirements as we can find them in the field of watchmaking.

European patent application EP 0 625 738 in the name of the Applicant describes a vibrating device of a unit such as a watch. This device includes an electromagnetically coupled coil with a ground mobile.

This patent application does not describe the characteristics of the coil excitation means. That said, the skilled person knows that it is necessary to apply to the pulse coil whose frequency is equal to the natural frequency of oscillation of the coil-mass assembly mobile to obtain maximum amplitude of vibration for a given amount of energy supplied.

Now it turns out that in practice this frequency clean is difficult to determine rigorously. All first, it varies from a moving coil-to-ground assembly to the other because of the manufacturing tolerances, which are around 15%.

Then it varies depending on how this set is worn, and more or less integrates with the wearer. Typically, the conditions to wear induce variations of the order of 5% of the frequency clean of the whole, as well as a variation of the energy dissipated in the carrier.

These variations decrease the return on resources coil excitation designed to operate at frequency fixed, resulting in significant loss of energy.

The object of the present invention is to remedy these disadvantages.

This object of the invention is achieved, as well as other which will appear on reading the following, with a non-audible alarm device, intended to equip a body-worn unit such as a timepiece or a mobile phone, including a case, a ground mobile inside this case intended for him transmit vibrations, a coupled coil electromagnetically to said moving mass to make it oscillate, and an excitation circuit of said coil, this device being characterized in that it comprises also means for measuring the instantaneous frequency of oscillation of the moving coil-earth assembly during the current oscillation, as well as means for generate during the following oscillation a series of excitation pulses from said coil, the characteristics are a function of the measurement of said instantaneous frequency of oscillation.

Thanks to these characteristics, it becomes possible to make a non-audible alarm device requiring little of energy and operating with good efficiency, which allows to consider using it in particular in small timepieces, such as watches.

• la figure 1 représente le circuit d'excitation de la bobine du dispositif selon l'invention, ainsi qu'un circuit de mesure connecté à ses bornes;
• la figure 2 représente le diagramme du principe de fonctionnement du dispositif selon l'invention; et
• les figures 3 à 13 représentent les organigrammes d'un programme informatique destiné à fonctionner en interface avec les circuits d'excitation et de mesure de la bobine, en accord avec le principe de fonctionnement indiqué par le diagramme de la figure 2. La figure 3 représente l'organigramme du programme principal, et les figures 4 à 13 représentent les organigrammes de sous-programmes rattachés directement ou indirectement au programme principal.

Other characteristics and advantages of the present invention will appear on reading the description which follows and the appended drawings given solely by way of example, and in which:

• FIG. 1 represents the excitation circuit of the coil of the device according to the invention, as well as a measurement circuit connected to its terminals;
• FIG. 2 represents the diagram of the operating principle of the device according to the invention; and
• FIGS. 3 to 13 represent the flowcharts of a computer program intended to operate in interface with the excitation and measurement circuits of the coil, in accordance with the operating principle indicated by the diagram in FIG. 2. FIG. 3 represents the flowchart of the main program, and FIGS. 4 to 13 represent the flowcharts of subprograms attached directly or indirectly to the main program.

In these figures, identical reference numbers represent identical organs or elements or analogues.

In a preferred embodiment, the device according to the invention comprises structural members analogous to those described in the patent application European EP 0 625 738 mentioned above. It thus includes a housing (not shown), a moving mass inside of this case intended to transmit vibrations to it (not shown), and a coupled coil L electromagnetically to this moving mass.

This coil is shown schematically on the figure 1. Its first B1 and second B2 terminals are likely to be brought to zero voltage or to a voltage VBB according to the states of four transistors of power Q1, Q2, Q3, Q4.

These transistors are controlled by a logic of LC command typically comprising first U1A and second U1B inverters, as well as first U2A and second U2B logic gates "OR".

Depending on the first DIAG1, second DIAG2 and third SHORT input signals applied to the LC control logic, the power transistors Q1, Q2, Q3, Q4 and the coil L occupy the states indicated by the following truth table: DIAG1 DIAG2 SHORTS Q1 Q2 Q3 Q4 COIL L 0 0 0 high impedance 1 0 0 B1 = VBB; B2 = 0 0 1 0 B1 = 0; B2 = VBB 0 0 1 short circuit

The first B1 and second B2 terminals of the coil L are also connected to a measuring circuit comprising a differential amplifier U3 and first U4 and second U5 comparators.

The amplifier U3 restores the induced voltage UIND measured between the coil terminals (see curve 2-1 on Figure 2).

The first comparator U4 compares the induced voltage UIND to 0. It provides an output signal COMP1, which is worth 1 when the induced voltage UIND is positive, and which is worth 0 when this voltage is negative (see curve 2-2 on Figure 2).

The second comparator U5 compares the induced voltage UIND at a reference voltage REFA. It provides a signal COMP2 output, which is equal to 1 when the induced voltage UIND is greater than REFA, and which is 0 in the case otherwise (see curve 2-3 in Figure 2).

The excitation and measurement circuits described above interface with a unit likely to run a computer program, such than a microprocessor or a microcontroller M.

The object of what follows is the description of such computer program allowing, from a signal ALARM for activating the device according to the invention and COMP1 and COMP2 output signals, to control in the time the input signals DIAG1, DIAG2 and SHORT from so as to oscillate the moving coil-earth assembly in providing the minimum amount of energy.

In the following description, the references to different program operations are indicated between parentheses.

This description will be usefully clarified by the diagram of figure 2. Reference will therefore be made to it as often as possible.

As can be seen in Figure 3, previously for any operation, the main program (3-1) begins with an initialization of its internal variables (3-2).

Then the main program tests the ALARM signal (3-3), which is 1 when the device according to the invention is activated, and 0 otherwise. If ALARM is 0, the program principal repeats the test; if ALARM is 1, the main program executes the BALANCE subroutine (3-4) which is detailed in Figure 4.

The BALANCE subroutine begins by setting the signal SHORT at 1 (4-1), the two signals DIAG1 and DIAG2 having also been set to 0 during the step initialization (3-2). Referring to the table of truth above, we see that we put the coil L short circuit, which has the effect of suffocating a possible movement of the moving coil-earth assembly.

We then wait for a period T1 (4-2) sufficient for the assembly to come to rest, then the SHORT signal is set to 0 (4-3): the coil-ground assembly mobile is then ready to oscillate freely.

Then, we put the signal DIAG2 to 1 (4-5). At the end with a duration T2 (4-6), this signal is reset to 0 (4-7). We thus sends a first impulse - called positive by convention - to the moving coil-earth assembly.

At the end of a duration T3 (4-8), we put the signal DIAG1 to 1 (4-9). At the end of the T2 period (4-10), we reset this signal at 0 (4-11). So we send a second impulse to the moving coil-earth assembly, of sign opposite to that of the first impulse.

We choose T2 and T3 so that their sum is substantially equal to a nominal half-period of oscillation of the moving coil-earth assembly. Through example, in the typical case where this set has a nominal natural frequency of 166 Hz, i.e. a nominal natural period of 6 ms, you can choose T3 = 2 ms and T2 = 1 ms.

After sending these two pulses, we expect new during duration T3 (4-12). Then we initialize a internal variable VAR5 by giving it a certain value MAX (4-13). This internal variable will make it possible to define the width of the pulses which will be later sent to the moving coil-earth assembly.

Then, we put an internal variable PHASE at 1 (4-14). This internal variable will allow you to select subroutines.

Then, we put an internal variable CPT1 at 0 (4-15). This internal variable will play a counter role.

Then, we put an internal variable PUL at 0 (4-16). This internal variable only goes to 1 when the signal COMP1 goes to 1, i.e. at the moment when the voltage induced UIND across coil L becomes positive (see figure 2 (2-4)).

The PUL variable is tested (4-17). As long as she is not equal to 1, the test is repeated. When she becomes equal to 1, in this case when UIND passes from a negative value to a positive value for the first time after the first oscillation period, the BALANCE subroutine resets the PUL variable to 0 (4-18), then return to the main program (4-19).

We now understand that the BALANCE subroutine has essential function of putting the coil-ground assembly mobile in free oscillation. By sending two pulses at a time interval substantially equal to the nominal own half-period of the coil-earth assembly mobile, we are sure to get a free oscillation of suitable amplitude.

After execution of the BALANCE sub-program, the main program again tests the ALARM signal (3-5). If ALARM is reset to 0, i.e. if there is no longer instead of activating the device according to the invention, the program sets signals DIAG1 (3-6) and DIAG2 (3-7) to 0, and sets the signal SHORT (3-8) to 1. We thus suffocate oscillations of the moving coil-earth assembly.

If the ALARM signal is kept at 1, i.e. if there is reason to continue the activation procedure of the device according to the invention, the main program waits for the appearance of a TIC signal (3-6 and 3-7) from of a time base. Typically, this time base is quartz type, and it can also be used to control other functions related to those of the device according to the invention. For example, in case this device is intended to equip a timepiece such as a watch, the time base will allow you to control a time display using the frequency divider usual.

• si PHASE vaut 1 (5-1), on exécute le sous-programme PHASE1 (5-2);
• si PHASE vaut 2 (5-3), on exécute le sous-programme PHASE2 (5-4);
• si PHASE vaut 3 (5-5), on exécute le sous-programme PHASE3 (5-6);
• si PHASE vaut 4 (5-7), on exécute le sous-programme PHASE4 (5-8);
• si PHASE vaut 5 (5-9), on exécute le sous-programme PHASE5 (5-10);
• si PHASE n'est égal à aucune valeur comprise entre 1 et 5 (cas d'erreur), le programme principal est réinitialisé (5-11).

When the TIC signal arrives, the main program executes the SELPHASE subroutine (3-8) which concerns the phase selection. As can be seen in Figure 5, this subroutine tests the internal variable PHASE:

• if PHASE is worth 1 (5-1), the subroutine PHASE1 (5-2) is executed;
• if PHASE is 2 (5-3), execute the subroutine PHASE2 (5-4);
• if PHASE is 3 (5-5), execute the subroutine PHASE3 (5-6);
• if PHASE is 4 (5-7), execute the subroutine PHASE4 (5-8);
• if PHASE is 5 (5-9), execute the subroutine PHASE5 (5-10);
• if PHASE is not equal to any value between 1 and 5 (error case), the main program is reset (5-11).

When running the subroutine for the first time SELPHASE, the internal variable PHASE is worth 1: indeed, it was set to this value by the subroutine BALANCE (see above). Under these conditions, the subroutine SELPHASE starts by launching the subroutine PHASE1 (see Figure 6).

The PHASE1 subroutine begins by testing the internal variable PUL (6-1). If PULL is 0, we increment the internal variable CPT1 of a unit (6-2), then we returns to the main program (6-3). If PUL is 1, we launches the INIPER subroutine (6-4).

As can be seen in Figure 7, the subroutine INIPER, which concerns the initialization of the period, allows to calculate and initialize a certain number of internal variables. VAR1 (7-1) and VAR2 (7-2) are defined as being worth a quarter and a eighth of the content of CPT1; VAR3 is equal to the sum of VAR1 and VAR2 (7-3); VAR4 is equal to VAR5 (7-4); CPT1 is set to 0 (7-5); CPT2 is equal to VAR1 (7-6); and PHASE is set to 2 (7-7). Then the subroutine INIPER returns to the main program (7-8).

As we can now understand (see Figure 2 (2-5)), the sub-program PHASE1 allows you to totalize in the variable CPT1 the duration separating two passages consecutive of the PUL variable from 0 to 1, this duration being expressed in base units of time. We thus measure the period of the first free oscillation of the set moving coil-mass, i.e. its own period instantaneous oscillation.

The INIPER sub-program, which is launched after this instant clean period of oscillation has been calculated, used to define the characteristics of pulses that are going to be sent subsequently to the moving coil-earth assembly so as to bring it into forced oscillation. So, as we will see, VAR1 will determine the phase of these pulses, VAR4 their width, and VAR2 and VAR3 will be used to launch a procedure for safety in the event of a sudden disturbance inflicted on the unit worn close to the body fitted with the device according to the invention.

At the end of the repeated execution of the subroutine PHASE1 then that of the INIPER sub-program, the variable PHASE is 2. Therefore, the SELPHASE subroutine launches the PHASE2 sub-program.

As can be seen in Figure 8, the subroutine PHASE2 begins by incrementing the variable CPT1 by one unit (8-1), then by decrementing the variable CPT2 of a unit (8-2). Then, we test the variable CPT2 (8-3). If it is different from the variable VAR4, we compare to 0 (8-4). If it is different from 0, we returns to the main program (8-5). If it is equal to 0, we put the variable PHASE at 3 (8-6) before returning in the main program (8-5).

If the variable CPT2 is equal to the variable VAR4, we sets the DIAG1 signal to 1 (8-7) before returning to the main program (8-5).

As we can now understand (see Figure 2 (2-6)), the time taken by the variable CPT2 to go from the value VAR1 at 0 is equal to a quarter of the duration which elapsed during execution of the subroutine PHASE1, i.e. a quarter of the proper period instantaneous oscillation of the coil-ground assembly mobile.

We thus send a positive impulse (2-7) to this together at a time (2-8) preceding by a base unit time the end (2-9) of the first quarter of its period oscillation.

After repeated execution of the PHASE2 subroutine, the variable PHASE is worth 3. Therefore, the subroutine SELPHASE launches the PHASE3 sub-program.

As can be seen in Figure 9, the subroutine PHASE3 begins by incrementing the variable CPT1 by a unit (9-1), then increment the variable CPT2 of a unit (9-2). Then, we test the variable CPT2 (9-3). If it is different from the variable VAR4, we compare to variable VAR1 (9-4). If it is different from VAR1, we return to the main program (9-5). If she is equal to VAR1, we put the variable PHASE at 4 (9-6) before return to the main program (9-5).

If the variable CPT2 is equal to the variable VAR4, we sets the DIAG1 signal to 0 (9-7) before returning to the main program (9-5).

As we can now understand (see Figure 2 (2-10)), the time taken by the variable CPT2 to iron from the value 0 to VAR1 is also equal to a quarter of instantaneous clean period of oscillation of the assembly moving coil-ground.

We thus interrupt the positive impulse (2-7) sent to this set in the previous phase to a instant (2-11) following a unit of time base on start (2-9) of his second quarter period oscillation.

We thus managed to send to the coil-ground assembly moving a positive impulse (2-7) in phase with respect to its amplitude peak (2-12).

We see here that the value of VAR1 determines the instants 2-8 and 2-11 when the variable CPT2 is equal to the variable VAR4, and thereby the time position of the impulse 2-7 compared to the oscillation of the whole moving coil-ground.

After the repeated execution of the PHASE3 subroutine, variable PHASE is 4. Therefore, the subroutine SELPHASE launches the PHASE4 sub-program.

As can be seen in Figure 10, the subroutine PHASE4 starts by incrementing the variable CPT1 by one unit (10-1), then by decrementing the variable CPT2 of a unit (10-2). Then, we test the variable CPT2 (10-3). If it is different from the variable VAR4, we compare to 0 (10-4). If it is different from 0, we returns to the main program (10-5). If it is equal at 0, we put the variable PHASE at 5 (10-6) before return to the main program (10-5).

If the variable CPT2 is equal to the variable VAR4, we executes a LEVEL subroutine (10-7) before switching on the DIAG2 signal at 1 (10-8) then return to the program main (10-5).

FIG. 11 represents a first variant of the LEVEL subroutine. We start by testing the signal COMP2 (11-1). If this signal is not worth 1, i.e. if the induced voltage UIND across the coil L is lower than the reference value REFA, we put the internal variable VAR5 to the value MAX (11-2), then we returns to the PHASE4 subroutine (11-4). If this signal is equal to 1, that is to say if UIND is greater than REFA, we put the variable VAR5 to the value MIN (11-3), then we return in the PHASE4 sub-program (11-4).

Figure 12 shows a second variant of the LEVEL subroutine. We start by testing the signal COMP2 (12-1). If this signal is not worth 1, we compare the variable VAR5 at MAX value (12-2). If VAR5 is not equal to MAX, we increment it by one unit (12-3), then we returns to the PHASE4 subroutine (12-4). If VAR5 is equal to MAX, we return directly to the subroutine PHASE4 (12-4).

If COMP2 is equal to 1, we compare the variable VAR5 to the MIN value (12-5). If VAR5 is not equal to MIN, it is decrements by one (12-6), then returns to the subroutine PHASE4 (12-4). If VAR5 is equal to MIN, we returns directly to the PHASE4 subroutine (12-4).

As will be readily understood in the light of the description of the PHASE2 sub-program, the sub-program PHASE4 sends a negative pulse (2-13) to a instant (2-14) preceding by a base unit of time the end (2-15) of the third quarter of the oscillation period of the moving coil-earth assembly.

The role of the LEVEL sub-program is to regulate the amplitude of the oscillation of this set.

Indeed, by referring to the organizational chart of the sub-program INIPER (figure 7), we see (7-4) that VAR5 is in sets the value assigned to VAR4 during initialization variables that takes place at the start of each new oscillation period of the moving coil-earth assembly.

However, it is clear from the above that the VAR4 value determines the start and end times pulses sent to this set, and therefore their duration. Referring to Figure 2 (see 2-8 and 2-11), we understands that this duration increases when VAR4 increases, and vice versa.

Now, the amplitude of the oscillations of the whole moving coil-mass directly depends on the duration of pulses sent to it: the longer this duration the larger, the greater this amplitude, and Conversely.

Thus, it appears that the two variants of the subroutine LEVEL allow, by playing on the value of the variable VAR5, to regulate the amplitude of the oscillations of the moving coil-earth assembly. This regulation can be done either binary, with a high MAX level and a low level MIN (variant of FIG. 11), either of gradually, with intermediate values between these two levels (variant of the figure 12).

At the end of the repeated execution of the subroutine PHASE4 then that of the LEVEL subroutine, the variable PHASE equals 5. Therefore, the SELPHASE subroutine launches the PHASE5 sub-program.

As can be seen in Figure 13, the subroutine PHASE5 starts by incrementing the variable CPT1 by a unit (13-1), then increment the variable CPT2 of a unit (13-2). Then, we test the variable CPT2 (13-3). If it is different from the variable VAR4, we compare to variable VAR2 (13-4). If it is higher to VAR2, we compare it to VAR3 (13-5). If she is different from VAR3, we test the variable PUL (13-6). Yes PUL is not worth 1, we return to the main program (13-7). If PUL is 1, the INIPER subroutine is executed (13-8) before returning to the main program (13-7).

If the variable CPT2 is equal to the variable VAR3, we resets the main program (13-9).

If the variable CPT2 is greater than the variable VAR2, set the PUL variable to 0 (13-10), then return in the main program (13-7).

If the variable CPT2 is equal to the variable VAR4, we set signal DIAG2 to 0 (13-11), then return to main program (13-7).

As will be readily understood in the light of the description of the PHASE3 sub-program, the sub-program PHASE5 allows to interrupt the negative pulse (2-13) sent to the moving coil-earth assembly during the phase preceding at an instant (2-16) succeeding by a unit of time base the start (2-15) of its fourth quarter oscillation period.

We thus managed to send to the coil-ground assembly moving a negative pulse (2-13) in phase with respect at its amplitude trough (2-17), that is to say at the maximum negative of the induced voltage. Of course, the maximum of the induced voltage corresponds to the maximum speed of the moving coil-earth assembly.

In addition, the two variables VAR2 and VAR3 define first (2-18) and second (2-19) moments symmetrically framing the moment (2-20) when the variable CPT2 reaches the value VAR1, i.e., theoretically, the instant the fourth quarter of the period ends the forced oscillation of the moving coil-earth assembly and where PUL returns to 1.

If this set is strongly disturbed in its oscillation, by a sudden external jolt by example, when PUL goes back to 1 may be strongly offset from its theoretical position.

The subject of successive tests of the PHASE5 sub-program is to locate the moment when PUL goes back to 1 compared to instants 2-18 and 2-19.

If this moment is before instant 2-18 or after time 2-19, i.e. if the variable CPT2 reaches VAR3 before PUL returns to 1 (test 13-5), this means that the coil-ground assembly has undergone a disruption likely to materially change its instantaneous natural frequency of oscillation: so measure it again by relaunching the whole program (13-9).

If this moment is between instants 2-18 and 2-19 (test 13-6), the INIPER subroutine is executed, and calculates the parameters of the following period, notably from the totalized duration in the variable CPT1.

In this case, the PHASE2 sub-program succeeds new to sub-program PHASE5, and the cycle repeats similar to itself, adapting from period to period its parameters at the oscillation frequency of the whole moving coil-mass, as well as the amplitude of this oscillation.

We now understand that the adjustment of the impulses sent to the moving coil-earth assembly is obtained by to three different procedures.

The first procedure, which occurs at the start of activation of the device according to the invention or during a brutal disturbance, allows to adapt the frequency and the time position of the pulses as a function of characteristics of the free oscillation of the assembly moving coil-ground.

The second procedure, which occurs during the setting in forced oscillation this set, allows to correct the frequency and phase of the pulses at the start of each new period.

The third procedure, which also takes place during the forced oscillation of the assembly moving coil-mass, allows to adjust its amplitude oscillation.

These three adjustment procedures could be implemented independently of each other. That said, they appear to be perfectly complementary vis-à-vis the aim sought by the invention, which is to create a device with optimal energy efficiency.

The device according to the invention is stopped as soon as the ALARM signal goes to 0 in the program main. The signals DIAG1 and DIAG2 are then set to 0 and the SHORT signal is set to 1, quickly suffocating the oscillation of the moving coil-earth assembly. The main program then runs in a waiting loop waiting for a new passage of the ALARM signal to 1.

Of course, the invention is not limited to the modes of realization described and represented which was given only as an example. For example, only one or more than two pulses per period could be sent to the moving coil-earth assembly.

Claims (10)

Non-audible alarm device, intended to equip a body-worn unit such as a coin or a cell phone, including a housing, a moving mass inside this housing intended to transmit vibrations to it, a coil (L) electromagnetically coupled to said moving mass for oscillate it, and an excitation circuit for said coil, characterized in that it comprises means for measure the instantaneous oscillation frequency of the moving coil-mass assembly during oscillation in course, as well as ways to spawn during the following oscillation a series of excitation pulses of said coil whose characteristics are a function of the measurement of said instantaneous frequency oscillation. Device according to claim 1, characterized in that it includes means for sending at least one impulse to the coil (L) prior to activation forced oscillation of the moving coil-earth assembly or following a brutal disturbance suffered by said unit worn close to the body, to measure the natural frequency instantaneous oscillation of said assembly. Device according to claim 2, characterized in that it includes means for sending to the reel (L) prior to the forced oscillation of the moving coil-earth assembly or following a brutal disturbance suffered by said unit carried near the body two impulses of signs opposite to an interval of time substantially equal to the nominal own half-period of oscillation of the moving coil-earth assembly. Device according to any one of previous claims, characterized in that includes a time base, means for testing the sign of induced voltage (UIND) across the coil (L) and a first counter (CPT1) activated at each signal (TIC) of the time base, this counter totaling the duration separating at least two consecutive sign changes from said induced voltage, thus making it possible to measure the instantaneous frequency of oscillation of the coil-ground assembly mobile. Device according to any one of previous claims comprising a second counter (CPT2) activated on each signal (TIC) from a base time and set according to the measurement of the instantaneous frequency of the previous oscillation of the moving coil-earth assembly, characterized in that it includes means allowing, depending on the value of this second counter, to trigger a series of excitation pulses from the coil (L) (2-7, 2-13) of same frequency as said instantaneous frequency. Device according to claims 4 and 5, characterized in that: the second counter (CPT2) is fixed, at each start of oscillation of the moving coil-earth assembly, as being equal to a first variable (VAR1) equal to a quarter of the value reached by the first counter (CPT1) at the end of the previous oscillation, said second counter goes from said first variable to 0 then from 0 to this first variable twice in succession, each passage during a quarter of the period of said previous oscillation, a first pulse of a first given polarity (2-7) is sent to the coil (L) between first (2-8) and second (2-11) times when said second counter is equal to a second variable (VAR4 ) less than said first variable, a second pulse of a second reverse polarity (2-13) is sent to said coil between third (2-14) and fourth (2-16) times when said second counter is equal to said second variable,
so as to make said first and second pulses substantially coincide with the two maxima of the voltage induced by the movement of said moving coil-mass assembly. Device according to claim 6, characterized in that it includes means for adjusting the value of the second variable (VAR4) - and therefore the duration separating on the one hand the first instant (2-8) of the second instant (2-11) and on the other hand the third instant (2-14) of fourth instant (2-16) - depending on the amplitude of the previous oscillation of the coil-mass assembly mobile, in order to adjust the amplitude of the oscillation in Classes. Device according to any one of claims 5 to 7, characterized in that it comprises means to reset the excitation procedure of the coil (L) in case of strong disturbance inflicted on the moving coil-earth assembly. Device according to claim 8, characterized in that it includes means for comparing the instant when the induced voltage (UIND) actually changes sign in end of period compared to fifths (2-18) and sixth (2-19) moments framing the theoretical instant (2-20) where this passage would take place in the absence of any disturbance. Device according to any one of previous claims, characterized in that the coil (L) is controlled by a duly programmed unit such as a microcontroller (M).

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