HK1082966B

HK1082966B - Process of detection of a dive start in a dive computer

Info

Publication number: HK1082966B
Application number: HK06102921.4A
Authority: HK
Inventors: Claude Stéphane; Christe Laurent
Original assignee: Eta Sa Manufacture Horlogere Suisse
Priority date: 2004-03-22
Filing date: 2006-03-07
Publication date: 2010-12-24

Description

Procedure for detecting the start of a dive in a dive computer

Technical Field

The present invention relates to a method for detecting the start of a dive implemented in a portable electronic device of the diving computer type. More specifically, the method is performed in such an apparatus having at least a first mode of operation and a second mode of operation (referred to as a dive mode). The device comprises in particular: a pressure sensor for measuring an ambient pressure value and an electronic circuit for processing pressure measurements, comprising a time base and at least one memory area.

The detection method according to the invention is based on the study of the variation of the ambient pressure as a function of time to detect the start of a dive causing a significant increase in the value of the ambient pressure.

The invention also relates to a portable electronic device specially adapted to implement the aforementioned method.

Background

Such methods of detecting the start of a dive using various physical principles are known in the art.

European patent 0689109, granted on 16.12.1998, to city of west metro clock (CITIZEN WATCH co. ltd.) discloses a method of this type, and a portable electronic device for implementing the method. In particular, the device is provided with specific means for detecting when the device is in contact with water and a pressure sensor for measuring the value of the ambient pressure. According to this patent, in a first operating mode, the pressure sensor is supplied with power so as to perform a measurement of the atmospheric pressure once per hour, storing the value thus obtained as a reference pressure value. Furthermore, power is permanently or periodically supplied to a specific water detection device, which may for example take the form of a resistive contact provided on the housing of the device.

The resistive contacts thus perform the main switching function of the circuit (in particular the pressure sensor) dedicated to the operation mode related to diving. In fact, when the presence of water is detected at the resistive contacts, the power supply frequency of the pressure sensor is changed, in the range of the operating mode called the preparation mode, so that the measurement of the ambient pressure is performed with a period of the order of seconds. These measurements allow to calculate the pressure variation value between the most recently measured value and the most recently stored reference pressure value, which variation value is then compared with a predetermined value constituting the dive mode triggering threshold. When the pressure change exceeds the trigger threshold, the dive mode is activated. In the opposite case, the sensor is still powered for a few minutes to monitor the development of the ambient pressure. Once this period has elapsed, the stand-by mode is exited and the pressure sensor is again powered on an hourly basis.

This detection method makes it possible to distinguish between a situation in which, for example, the person wearing the device wets it by washing his hands and a situation which actually corresponds to the start of a dive. In the latter case, the pressure measurement performed by the pressure sensor enables the start of a dive to be effected after activation of the preparation mode, in the case where the device is first in contact with water before seeing an increase in the ambient pressure.

However, such devices have significant drawbacks from a structural point of view, due to the need to provide specific means for detecting the presence of water on the casing. In the aforementioned case of the use of resistive contacts, it is in fact necessary to provide specific means to ensure that the casing of the device is waterproof in the region of these contacts, which has a significant impact on the manufacturing costs of such devices. The method described above therefore has similar drawbacks, since it is based on the implementation of specific means for detecting the presence of water.

Other methods and devices exist in the prior art that do not implement such specific means for detecting the presence of water but use ambient pressure measurements to detect the start of a dive.

In particular, devices of this type are also known, in which a pressure sensor is periodically supplied with power to measure the value of the ambient pressure and store the result of such a measurement. These means are used to calculate the value of the change between the most recent measurement value and the previous one at each new measurement of the ambient pressure and to compare it with the value determining the triggering threshold. Once the trigger threshold has been exceeded, the dive mode is activated and the penultimate measured pressure value is generally stored as the reference pressure, i.e. it is assumed that this value corresponds to the surface pressure of the body of water in which the dive takes place.

However, this type of device also has drawbacks because the accuracy of detecting the start of a dive is based entirely on the stored trigger threshold value.

Thus, if the value of the threshold is too low, the device risks the dive mode being triggered unintentionally. For example, if a person wearing such a device goes down a hill at a constant pace, the device will consider the corresponding pressure increase to be similar to that of entering water. On the other hand, if the value of the threshold value is too high, the trigger accuracy is liable to deteriorate if the user stays in the water near the water surface for a certain period of time before the start of diving. In such a case, the stored reference pressure value may also be incorrect, as the value is measured in water at a shallower depth than the depth of the trigger threshold. Depending on its magnitude, such errors can have dangerous consequences for the health of the person wearing the device, especially from the point of view of the data relating to the cessation of decompression (decompression stop).

Disclosure of Invention

A first object of the present invention is to overcome the aforementioned drawbacks of the prior art by proposing a method for detecting the start of a dive with improved accuracy and performing this detection on the basis of measured ambient pressure values, and a portable electronic device suitable for implementing such a method.

Accordingly, the present invention provides a method of the type mentioned above, comprising the steps of:

a) measuring an ambient pressure value and storing the value as a reference pressure value;

b) periodically measuring an ambient pressure value at a first frequency;

c) periodically calculating a pressure variation value between the measured ambient pressure and a reference pressure at a first frequency and comparing said pressure variation value with a predetermined value, called trigger threshold, stored in a memory area;

d) activating a dive mode if said pressure variation value is higher than said trigger threshold, otherwise in the opposite case, continuing with step e);

e) comparing the pressure variation value with a predetermined amount stored in a storage area or an average value of pressure variation determined from measured pressure values at a second frequency, the predetermined amount being lower than a trigger threshold, the second frequency being lower than or equal to the first frequency;

f) correcting a reference pressure value if the pressure variation value is higher than the predetermined amount or the pressure variation average value; otherwise, in the opposite case, the most recently measured pressure value is stored as the new reference pressure value, and then

g) Returning to the step b).

Optionally, in step e), the calculated absolute value of the pressure change is compared with a predetermined amount stored in the memory area or determined from the measured pressure value.

Thus, according to this detection method, the reference pressure value is not systematically updated at a given frequency. In order to correct the measured ambient pressure value before storing it as the reference pressure, the calculated pressure change needs to be taken into account. The detection of the start of a dive according to the invention thus achieves an improved accuracy with respect to the previously described devices of the prior art.

Preferably, the method according to the present invention further comprises: after step d), the following steps are carried out:

d') periodically determining the sign of the pressure change at a third frequency, said third frequency being between said first and second frequencies;

d') if said pressure variation is negative, storing the most recently measured pressure value as the reference pressure value, and then returning to step b); otherwise in the opposite case, continue with step e).

These additional steps also improve the accuracy of the stored reference pressure value by increasing the likelihood of updating relative to the basic method.

According to a first variant of the invention, when said predetermined quantity is predetermined, the latter being referred to as a first correction factor, the correction in step f) comprises adding said first correction factor to the stored reference pressure value, the result of the addition being stored as a new reference pressure value.

According to a second embodiment of the invention, when determining said pressure variation mean value from the measured pressure values, step e) further comprises the operation of storing pressure variation values at said second frequency, at least the last three stored pressure variation values being used to calculate said pressure variation mean value. According to a preferred variant, the pressure variation mean corresponds to the result of the calculation of the mean pressure variation of the last three pressure variation values, the correction in step f) comprising the addition of the pressure variation mean to a stored reference pressure value, the result of the addition being stored as a new reference pressure value.

Drawings

Other characteristics and advantages of the invention will become better apparent from the following detailed description, given by way of non-limiting example, with reference to the accompanying drawings, wherein:

fig. 1 is a general schematic diagram of the electronic circuitry of a portable electronic device implementing the method according to the invention;

fig. 2 is a diagram schematically illustrating the steps of a method of detecting the start of a dive according to a first embodiment of the present invention;

fig. 3 is a diagram schematically illustrating the steps of a method of detecting the start of a dive according to a second embodiment of the present invention;

fig. 4 is a diagram schematically illustrating the steps of a method of detecting the start of a dive according to a third embodiment of the present invention.

Detailed Description

Fig. 1 schematically shows a general schematic of the electronic circuitry of a portable electronic device implementing the method according to the invention. In the example shown here, the portable electronic device takes the particular form of an electronic diver's watch 1 with an analog display, which comprises at least two operating modes: a first time mode and a second diving mode.

Of course, the method according to the invention is not limited to being implemented in a watch, but may also be implemented in any type of conventional portable diver computer without going beyond the scope of the invention.

In general, the electronic circuit of the watch 1 comprises an integrated circuit 2 comprising a controller circuit 3 capable of managing the traditional time functions of the watch 1, for which purpose the controller circuit 3 comprises a time division circuit and is connected to a resonator 4 providing a time base. From this time base, the controller circuit 3 generates time-dependent data, in particular for performing time-mode functions as well as functions related to the dive mode.

Furthermore, the controller circuit 3 receives at one input the signal generated by the pressure sensor 5, which pressure sensor 5 generates an analog electrical signal representing the ambient pressure. These signals are supplied to the input of the controller circuit 3 in the form of digital signals after passing through the analog-to-digital converter 6.

The pressure sensor 5 is of conventional type and the person skilled in the art will not encounter any difficulties in selecting a pressure sensor suitable for implementing the invention.

The integrated circuit 2 also comprises a memory area, in particular a first memory area 7, preferably of the non-volatile type, containing a program enabling the controller circuit 3 to perform calculations relating to the dive mode according to, for example, a decompression algorithm. The choice of reprogrammable non-volatile memory (e.g., flash or EPROM) enables the computing program to be later modified depending on the decompression algorithm used. The integrated circuit 2 preferably comprises at least one second memory area 8, which may also be of a non-volatile type, in which the results of the measurements and calculations made by the controller circuit 3 are stored. As an example, this second memory area 8 is provided for storing depth measurements and corresponding time-related measurements relating to the most recent dive or divers.

From the various input signals, the controller circuit 3 determines from the diving point of view the condition and state of the diver at each moment. For this purpose, the device may provide pressure measurements every 5 minutes, for example, in time mode, and every 2 minutes in dive mode. From all these cycle measurements and according to the program stored in the first memory area 7, the controller circuit 3 can determine a certain number of parameters related to the diver's health, i.e. in particular, for example, the rate of residual nitrogen dissolved in its body and the number of microfoam formed.

Moreover, in the example embodiment described, the watch 1 has a display of analog type, in particular comprising an hour hand 9 and a minute hand 10 controlled by a bidirectional motor (not shown). The controller circuit 3 is thus programmable to generate suitable signals for the control circuit 11 of the bidirectional motor, for example display information of the hour hand 9 and minute hand 10 in the first time mode in relation to the current time, and information in the second dive mode in relation to the dive. The watch also comprises a control member 12, for example a crown-crown, intended in particular to regulate the current time or to activate a specific function. By way of non-limiting example, fig. 1 shows three positions of the control member 12, indicated by A, B and C, position a being the rest position, position B being the unstable pushed-in position and position C being the stable pulled-out position.

The reader interested in the operation of this type of portable Electronic device may refer to, for example, european patent applications 1396766a1 and 1396767a1 entitled "Electronic diving watch with analog display", filed on 2002, 9, 4.9.a. In fact, since the method according to the invention involves a transition from the first operating mode to the dive mode, the latter operation will not be discussed in detail in this application.

Fig. 2 to 4 show schematic diagrams relating to three embodiments of the dive initiation detection method according to the invention, the description of which is provided by way of non-limiting example. These three methods allow the pressure measurements taken periodically by the pressure sensor 5 to be "filtered" to limit inadvertent triggering of a dive mode, such as may occur when descending a hill quickly using some devices of the prior art. Also, these methods aim to prevent the devices implementing these methods from being able to detect the start of a dive, for example because the user has been in the water at the surface for a period of time before actually starting a dive.

Fig. 2 shows a schematic diagram depicting the main steps of a method of detecting the start of a dive according to a first embodiment of the present invention.

When the watch is in time mode, the controller circuit 3 is programmed to periodically supply power to the pressure sensor 5 to perform a measurement of the value of the ambient pressure.

The method starts at a phase a, indicated by the reference 20 in the figure, and the value of the pressure measured beforehand is stored as the reference pressure Pref. Furthermore, a first counter (not shown) is provided for measuring the first time interval T1, which counter has a value T1 between 0 and T1 at phase a, T1 being the measurement period value. Preferably, the period T1 is substantially between 0.1 and 10 seconds.

Starting from phase a, the controller circuit 3 checks the value of the first counter, step 21 in the figure. When the value of the counter is not equal to T1, the method returns to step a, preferably but not limited to, incrementing the value of the counter 1 time every second.

When the value of the first counter reaches the value T1, at step 22 in fig. 2, T1 is reset to 0.

Then, in step 23, power is supplied to the pressure sensor 5 to perform measurement of the ambient pressure P. In step 24, on the basis of the measurements performed, the controller circuit 3 calculates the pressure variation dP on the basis of the most recently measured pressure measurement and the previously stored reference pressure Pref.

The controller circuit 3 then compares the calculated pressure variation value dP with a predetermined value S, called trigger threshold, and corresponding to a water depth preferably comprised between 0.2 and 1.5 meters, step 25.

When the pressure variation dP exceeds the trigger threshold S, the dive mode is activated in step 26.

In the opposite case, i.e. when the pressure variation value dP is smaller than the trigger threshold S, the controller circuit 3 performs an additional check on the pressure variation value dP in step 27. More specifically, at step 23, the controller circuit determines the sign of dP, which is preferably performed at the same frequency as the ambient pressure measurement. Alternatively, however, the frequency of the test 27 may be different from the frequency of the ambient pressure measurements without departing from the scope of the present invention.

On the one hand, when the result of the check 27 indicates that the value of dP is negative, which corresponds to a decrease in pressure between the last stored reference pressure measurement Pref and the last performed ambient pressure measurement P, this P value is stored as a new reference value Pref, step 28.

It should be noted that in step 29 of fig. 2, the value t2 of the second counter (the function of which will be explained later) is checked. When the value T2 is equal to the value T2 corresponding to the second calculation frequency of the detection method according to the invention, T2 is reset to 0 at step 30, and the method is then restarted at a. When the value T2 of the second counter is less than T2, then the method resumes directly at a by performing T2 plus 1.

On the other hand, when the result of test 27 indicates that the value of dP is positive or zero, which corresponds to an increase or absence of pressure between the most recently stored reference measurement Pref and the most recently performed ambient pressure measurement P, the controller circuit goes to the additional test of step 31.

The additional check 31 consists in checking whether the value T2 of the second counter has reached a value T2, the value T2 corresponding to a frequency f2 at which the stored reference value can be corrected, the second frequency f2 being less than the frequency f1 at which the measurement of the ambient pressure value P is carried out.

From the viewpoint of correcting the reference pressure value Pref, in order to make the pressure change have a considerable value, the frequency f2 must be sufficiently low, in other words, the corresponding period T2 must be sufficiently long. Preferably, T2 values substantially between 30 seconds and 10 minutes, i.e. a frequency f2 in the order of 0.001 to 0.04Hz, are used.

When the value T2 is less than T2, the method starts again directly at a by performing T2 plus 1.

When the value of T2 equals T2, at step 32 the controller circuit 3 performs a new calculation aimed at assessing the recent behaviour of the ambient pressure value with respect to the average behaviour of the ambient pressure value over a longer period of time. For this purpose, the controller circuit 3 stores the most recently calculated pressure variation value dP in the memory area 8, for which purpose the memory area 8 preferably comprises at least 4 slots (slots). Thus, the most recently calculated pressure change value dP is stored by replacing the oldest dP value still in memory. The controller circuit then calculates the average value dPm of the pressure change from the last four stored values labeled dPi-3, dPi-2, dPi-1, and dP by simply adding them and dividing the result of the addition by 4.

From the value dPm calculated above, the controller circuit 3 compares this average value with the most recently calculated pressure change value dP in step 33.

When the most recent pressure change value dP is less than dPm, the reference pressure value Pref is updated with the most recently measured ambient pressure value P at step 34. Once the update is over, the value t2 of the second counter is reset to 0 at step 30 and the method starts again at phase a.

When the most recent pressure change value dP is higher than dPm, the next step 35 is to correct the reference pressure value Pref. In this case, it is assumed that the most recently calculated pressure variation is too large with respect to the variation considered over a longer period of time, which is why this variation does not propagate completely to the stored reference pressure value Pref. Therefore, the average value dPm calculated at step 32 is added to the most recently stored reference pressure value in consideration of the latest tendency of the ambient pressure variation value, and the result of this addition is stored as a new reference pressure value Pref. The effect of this correction is to "smooth" the changes in the reference pressure value Pref to filter sudden ambient pressure changes.

Once the reference pressure value Pref is corrected, the value t2 of the second counter is reset to 0 at step 30 and the method starts again at a.

In the check performed in step 25, this set of steps will be repeated indefinitely when the pressure variation value dP calculated in step 24 does not exceed the trigger threshold S.

According to a preferred variant of the method just described, the pressure change values dPi-3, dPi-2, dPi-1 and dP stored in memory area 8 are replaced by zero during the execution of step 28, i.e. when the controller circuit 3 determines in step 27 that the most recently calculated pressure change value is negative.

The general working principle of the method according to this embodiment is based on the fact that the ambient pressure will increase considerably at the start of a dive. Thus, the dive mode is activated when the pressure value changes rapidly by a value sufficient to exceed the trigger threshold. In the opposite case, the two cases can be distinguished, namely a first case in which the ambient pressure is reduced and a second case in which the ambient pressure is moderately increased.

In the first case, it is assumed that the user is not in the water but at an increased height. Then, the stored reference pressure value Pref is updated at a relatively high frequency, i.e., a frequency in the order of several seconds, so that the stored value represents the actual atmospheric pressure value with high accuracy. Such measurements are well documented, for example, when a person wearing the apparatus implementing the method rides in a lake at high altitude to dive.

In the second case, a moderate increase in ambient pressure can be attributed to two different causes: either into the water to stop at a shallow depth or to descend quickly on the ground, as for example when riding a vehicle down a hill quickly or during movement in the air. Since the reference pressure is only updated at a relatively low frequency compared to the frequency of the ambient pressure measurements, the method according to the invention is able to take these situations into account. Further, when the increase in the ambient pressure becomes too large, the increase propagates to the stored reference pressure value Pref but is attenuated thereby. Thus, during processing by the controller circuit, changes in ambient pressure are taken into account when performing some smoothing.

Due to this measure, the detection of the start of a dive can be ensured with high reliability, and unintentional triggering of the dive mode is also largely limited.

Fig. 3 shows a schematic diagram depicting the main steps of a method of detecting the start of a dive according to a second embodiment of the present invention.

Since the first few steps of the method according to the present embodiment, up to the comparison of the pressure change value with the trigger threshold S at step 25, are the same as in the first embodiment, these steps will not be described in detail. In addition, the reference numerals of these steps used in the first embodiment are also carried over to fig. 3.

When the pressure variation value dP is less than the trigger threshold S, which corresponds to an increase or a lack of change in pressure between the most recently stored reference pressure value Pref and the most recently performed ambient pressure measurement value P, the controller circuit goes to an additional check at step 40.

The additional check 40 consists in checking whether the value T2 of the second counter has reached a value T2, this value T2 corresponding to the frequency f2 at which the stored reference pressure value can be corrected. This second frequency f2 is smaller than the frequency f1 at which the ambient pressure measurement P is performed.

The frequency f2 here is of the same order of magnitude as the frequency f2 in the first embodiment. Preferably, T2 values substantially between 30 seconds and 10 minutes, i.e. a frequency f2 in the order of 0.001 to 0.04Hz, are used.

When the value of T2 equals T2, the controller circuit 3 resets the value of the second counter, T2, at step 41, and then performs a new calculation, at step 42, aimed at evaluating the behaviour of the recent ambient pressure value with respect to the average behaviour of the ambient pressure value over a longer period of time. This step 42 is similar to the related step 32 described in the first embodiment. The controller circuit 3 stores the most recently calculated pressure change value dP in a memory area 8, for which purpose the memory area 8 preferably comprises at least 4 slots. Thus, the most recently calculated pressure change value dP is stored by replacing the oldest dP value still in memory. The controller circuit then calculates the average value dPm of the pressure change from the last four values dPi-3, dPi-2, dPi-1 and dP in memory by simply adding them and dividing the result of the addition by 4.

From the value dPm calculated above, the controller circuit 3 compares the absolute value of this average value with the absolute value of the most recently calculated pressure change value dP in step 43.

When the absolute value of the most recent pressure change dP is less than the absolute value of dPm, the reference pressure value Pref is updated with the most recently measured ambient pressure value P at step 44. Once the update is over, the method starts again at step a.

When the absolute value of the latest pressure change value dP is higher than the absolute value of dPm, step 45 is a step of correcting the reference pressure value Pref. In this case, it is in fact assumed that the most recently calculated pressure variation value is too large with respect to the variation considered over a longer period of time, which is why this variation does not propagate completely to the stored reference pressure value Pref. Therefore, the average value dPm calculated at step 42 is added to the most recently stored reference pressure value in consideration of the latest tendency of the change in the ambient pressure value, and the result of the addition is stored as a new reference pressure value Pref. The effect of this correction is to "smooth" the changes in the reference pressure value Pref to filter sudden ambient pressure changes.

Once the reference pressure value Pref has been corrected, the method starts again at step a.

In the check performed in step 25, this set of steps will be repeated indefinitely when the pressure variation value dP calculated in step 42 does not exceed the trigger threshold S.

According to a preferred variant of the method just described, the pressure change values dPi-3, dPi-2, dPi-1 and dP stored in memory area 8 are replaced with zeros during the execution of step 44, i.e. when the controller circuit 3 determines that the most recently calculated pressure change value is low enough to replace the stored reference pressure value with the most recently measured ambient pressure value.

Two obvious variations in the method can be pointed out with respect to the description relating to the first embodiment.

On the one hand, it is to be noted that: the reference pressure value Pref is always updated at a frequency f2, which may result in a stored reference pressure value that is less accurate relative to the actual surface pressure in certain usage environments.

On the other hand, it is noted that: no distinction is made according to the sign of the calculated pressure change, as is the case with step 27 of the method according to the first embodiment. In practice, the comparison of the most recently calculated pressure variation dP with the mean value dPm is in absolute value. Therefore, the subsequent processing performed by the controller circuit 3 is the same regardless of whether dP is positive or negative. Therefore, smoothing of the ambient pressure variations occurs in both directions, in other words, all ambient pressure variations are attenuated before storing the average value dPm as the reference pressure, regardless of whether these variations correspond to a decrease or an increase in the ambient pressure.

Fig. 4 shows a schematic diagram depicting the main steps of a method of detecting the start of a dive according to a third embodiment of the present invention.

Since the first few steps of the method according to this embodiment are the same as in the first embodiment up to the determination of the sign of the pressure change in step 27, these steps will not be described in detail. In addition, the reference numerals of these steps used in the first embodiment are also carried over to fig. 4.

The method according to this embodiment differs from the two previous embodiments mainly in that: the nature of the quantity used to correct the stored reference pressure value, which here is a predetermined quantity, is no longer a quantity based on the measured ambient pressure value.

When the result of the test 27 indicates that the value of dP is negative, which corresponds to a pressure decrease between the most recently stored reference pressure value Pref and the most recently performed ambient pressure measurement value P, the most recently performed ambient pressure measurement value is stored as a new reference pressure value Pref at step 50.

It can be seen next at step 51 of fig. 4 that the controller circuit 3 assigns a particular value, here 6, to the value n of an additional counter, the function of which will be explained below.

In a preferred implementation variant, the value t2 of the second counter is then checked in step 52, similarly to what has been described in relation to the previous embodiment. When the value T2 is equal to the value T3 corresponding to the third update frequency f3, the value T2 is reset to 0 at step 53, and the most recently stored reference pressure value Pref is saved as the surface pressure P at step 54₀Surface pressure P₀For use as a reference in diving mode. After such an update (a step not indispensable for implementing the detection method according to the invention), the method restarts at a. When the value T2 of the second counter is less than T3, the method resumes directly at a by performing T2 plus 1. As mentioned above, T3 values between 30 seconds and 10 minutes, i.e. corresponding frequencies f3 in the order of 0.001 to 0.04Hz, are used.

On the other hand, when the result of test 27 indicates that the value of dP is positive or zero, which corresponds to an increase or absence of pressure between the most recently stored reference pressure value Pref and the most recently performed ambient pressure measurement value P, the controller circuit proceeds to an additional test at step 55.

An additional check 55 consists in detecting whether the value T2 of the second counter has reached the value a x T2, where a is an integer and T2 corresponds to a frequency f2 at which the stored reference pressure value can be corrected, this second frequency f2 being between the frequencies f1 and f 3.

From the viewpoint of correcting the reference pressure value Pref, in order to make the pressure change have a considerable value, the frequency f2 must be sufficiently low, in other words, the corresponding period T2 must be sufficiently long. Preferably, T2 values substantially between 30 seconds and 5 minutes, i.e. a frequency f2 in the order of 0.003 to 0.04Hz, are used.

When the value T2 is not a multiple of T2, the method resumes directly at a by performing T2 plus 1.

When the value T2 of the second counter is equal to a x T2, in other words it is a multiple of T2, a check 56 of the value n of the additional counter is carried out.

If the value n of the additional counter is not 0, the controller circuit performs another check according to the most recently calculated pressure change value dP in step 57. The value of dP is compared with a predetermined amount c1, the value of c1 corresponding to water depths of the order of 2 to 40 cm.

When the value of dP is less than c1, referred to as the first correction factor, as described above, at step 50 the end of the detection method is restarted, wherein the stored reference pressure Pref is updated with the most recently measured ambient pressure value P.

When the value of dP is greater than c1, the controller circuit performs a correction of the reference pressure value Pref by storing the sum of the most recently stored value Pref and the value of c1 as a new reference pressure value Pref at step 58. The value n of the additional counter is then decremented by 1 in step 59, and then returns to step 52 described earlier to continue at the end of the method.

Thus, it can be seen that: starting from the value n in the additional counter equal to 6, 6 consecutive passes through steps 57 to 59 are required to reduce the value n to 0.

At this stage, the result of the test at step 56 is different from the case just described, which modifies the steps after the test.

In practice, when the value n of the additional counter is equal to 0, step 56, the controller circuit 3 performs another check, step 60, on the basis of the last calculated pressure variation value dP. The pressure variation dP is then compared with a second predetermined quantity c2, called a second correction factor, where the value of c2 is between the values of c1 and S.

When the result of this test 60 results in a dP less than c2, the method returns to step 50 where the most recently measured ambient pressure value is stored as the new baseline pressure value Pref.

When the value of dP is higher than c2, execution continues with step 61, which constitutes an additional step of correcting the reference pressure value Pref. In this step, the sum of the most recently stored reference pressure value and c2 is stored as a new reference pressure value Pref.

After the correction step, the method continues by returning to step 52, which has been described.

Like the method according to the first embodiment, this method distinguishes the sign of the most recently calculated pressure change value dP, and the reference pressure is corrected only in the case where the ambient pressure change is not reduced.

The method according to this embodiment differs mainly from the previous embodiments in that: in the case where the ambient pressure value corresponds to a predetermined constant, the amount for correcting the reference pressure value Pref does not take into account the past development of the ambient pressure value.

Furthermore, it is clear that the steps relating to the use of an additional counter with value n are not indispensable for implementing the detection method according to the present embodiment, more particularly for the checking step 60 and the correction step 61.

In fact, the increase in the measured pressure P is propagated to the stored reference pressure value Pref to be attenuated. In other words, in order to smooth the increase in the ambient pressure, the correction step 58 (as in step 61) limits the increase in the reference pressure value to be stored with the value c 1.

Thus, in the special case where the ambient pressure increases in a quasi-continuous manner for several minutes, the stored reference pressure value will be further and further away from the actual ambient pressure value if only the correction mentioned in step 58 is performed.

This is why it is preferable to implement an additional correction step 61, in which correction step 61 the reference pressure value to be stored is also limited, but with a value c2 that is larger than c 1. This additional step can further improve the accuracy of the method according to the third embodiment.

The person skilled in the art will of course be able to achieve the surface pressure P in the preceding embodiments₀As described in step 54 of the present embodiment. Such precautions may in fact ensure a high accuracy of the value that is used in the following diving mode for depth calculation and for determining data relating to the safety of the person wearing the device.

The preceding description corresponds to a preferred embodiment of the invention, but must not be considered as limiting it in any way, in particular as regards the structure of the watch described, the functions described, the characteristics and the number of control elements used. As mentioned before, the detection method according to the invention can be implemented in any submersible computer type of portable electronic device, whether the display is analog or digital. Similarly, the invention is not limited to the described modes of operation, wherein these parameters may be modified by suitable programming of the controller circuit. The person skilled in the art does not encounter any particular difficulty in adapting the method according to the invention to his needs, in particular with respect to the values of the frequency and of the correction provided by way of example.

Claims

1. Method for detecting the start of a dive for a portable electronic device (1), said portable electronic device (1) having at least a first operating mode and a second operating mode, called dive mode, and comprising: a pressure sensor (5) for measuring an ambient pressure value (P); an electronic circuit (2) for processing the measurement results, comprising a time base (4) and at least one memory area (7, 8); the method carried out in the first mode of operation comprises the steps of:

a) measuring the value of the ambient pressure and storing this value as a reference value (Pref);

b) periodically measuring an ambient pressure value (P) at a first frequency (f 1);

c) periodically calculating, at a first frequency (f1), a pressure variation value (dP) between the measured ambient pressure (P) and a reference pressure (Pref) and comparing said pressure variation value (dP) with a predetermined value, called trigger threshold (S), stored in a storage area (7);

d) activating the dive mode if the pressure variation value (dP) is higher than the trigger threshold, otherwise in the opposite case, continuing with step e);

e) -comparing the pressure variation value (dP) with a predetermined quantity (c1) stored in the storage area (7) or with a pressure variation average value (dPm) determined from measured pressure values, at a second frequency (f2), wherein the predetermined quantity (c1) is lower than the triggering threshold (S), and the second frequency (f2) is lower than or equal to the first frequency (f 1);

f) correcting the reference pressure value (Pref) if the pressure variation value (dP) is higher than said predetermined amount (c1) or said pressure variation average value (dPm); otherwise, in the opposite case, the most recently measured pressure value (P) is stored as the new reference pressure value (Pref), and then

g) Returning to the step b).

2. The method of detecting the start of a dive according to claim 1, further comprising: the following steps are also included after the step d):

d') periodically determining the sign of the pressure change (dP) at a third frequency (f3), said third frequency (f3) being between said first and second frequencies (f1, f 2);

d') if said pressure variation (dP) is negative, storing the most recently measured pressure value as the reference pressure value (Pref) and then returning to step b); otherwise in the opposite case, continue with step e).

3. A method of detecting the start of a dive according to claim 1 or 2, wherein: when the predetermined amount (c1) is predetermined, the predetermined amount (c1) is referred to as a first correction factor (c1), and the correction in step f) includes adding the first correction factor (c1) to the stored reference pressure value, the result of the addition being stored as a new reference pressure value (Pref).

4. A method of detecting the start of a dive according to claim 3, wherein: completing steps e) to g) determines a cycle, during the execution of the last n-1 cycles, where n is an integer between 2 and 10, when a correction has been made to the reference pressure value, in one cycle of every n cycles, said first correction factor (c1) is replaced in steps e) and f) by an additional predetermined quantity, called second correction factor (c2), the value of said second correction factor (c2) being between said first correction factor and said triggering threshold.

5. A method of detecting the start of a dive according to claim 1 or 2, wherein: when the pressure variation mean value (dPm) is determined from measured pressure values, step e) further comprises the operation of storing the pressure variation value (dP) at the second frequency (f2), the stored at least the last three pressure variation values (dPi-2, dPi-1, dP) being used to calculate the pressure variation mean value (dPm) corresponding to the calculation of the mean pressure variation of the at least the last three pressure variation values, the correction in step f) comprising the addition of the pressure variation mean value (dPm) to the stored reference pressure value, the result of the addition being stored as a new reference pressure value (Pref).

6. A method of detecting the start of a dive according to claim 5, wherein: the pressure variation mean value (dPm) is calculated based on the stored last four pressure variation values (dPi-3, dPi-2, dPi-1, dP).

7. A method of detecting the start of a dive according to claim 6, wherein: when the sign of the most recently calculated pressure change (dP) in step d ") is negative, the stored pressure change values (dPi-3, dPi-2, dPi-1, dP) are all replaced with zero, and then return is made to step b).

8. A method of detecting the start of a dive according to claim 2, wherein: the first and third frequencies (f1, f3) are equal.

9. A method of detecting the start of a dive according to claim 1 or 2, wherein: the first frequency (f1) has a value substantially between 0.1 and 10 Hz.

10. A method of detecting the start of a dive according to claim 1 or 2, wherein: the second frequency (f2) has a value substantially between 0.001 and 0.04 Hz.

11. A method of detecting the start of a dive according to claim 1 or 2, wherein: the trigger threshold corresponds to a depth of water substantially between 0.2 and 1.5 meters.

12. A method of detecting the start of a dive according to claim 1 or 2, comprising an additional step, implemented at a third frequency (f3), in which the stored reference pressure value (Pref) is saved in an additional storage area for later use in a dive mode as the actual pressure value of the surface of the body of water undergoing dive.

13. Method for detecting the start of a dive for a portable electronic device having at least a first operating mode and a second operating mode, called dive mode, and comprising: a pressure sensor for measuring an ambient pressure value; an electronic circuit for processing the measurement results, comprising a time base and at least one memory area; the method carried out in the first mode of operation comprises the steps of:

a) measuring the ambient pressure value and storing this value as a reference value (Pref);

c) periodically calculating at said first frequency (f1) a value (dP) of the pressure variation between the measured ambient pressure (P) and a reference pressure (Pref) and comparing said pressure variation value (dP) with a predetermined value, called trigger threshold (S), stored in said storage area (7);

d) activating the dive mode if a pressure variation value (dP) is higher than the trigger threshold; otherwise in the opposite case, continue step e);

e) periodically comparing the absolute value of the pressure variation (dP) with the absolute value of a pressure variation mean value (dPm) determined from the measured pressure values at a second frequency (f 2);

f) -correcting the reference pressure value (Pref) if the absolute value of the pressure variation (dP) is higher than the absolute value of said pressure variation mean value (dPm); otherwise, in the opposite case, the most recently measured pressure value (P) is stored as the new reference pressure value (Pref), and then

g) Returning to the step b).

14. A method of detecting the start of a dive according to claim 13, wherein: step e) further comprises: -an operation of storing said pressure variation value (dP) at said second frequency (f2), at least the last three stored pressure variation values (dPi-2, dPi-1, dP) being used to calculate said pressure variation mean value (dPm), said correction in step f) comprising the addition of said pressure variation mean value (dPm) to a stored reference pressure value, the result of the addition being stored as a new reference pressure value (Pref).