WO2016198625A1

WO2016198625A1 - Weighing device and method for a touch screen terminal

Info

Publication number: WO2016198625A1
Application number: PCT/EP2016/063333
Authority: WO
Inventors: Ludovic BELLON
Original assignee: Universite Claude Bernard Lyon 1; Centre National De La Recherche Scientifique; Ecole Normale Superieure De Lyon
Priority date: 2015-06-10
Filing date: 2016-06-10
Publication date: 2016-12-15
Also published as: FR3037393A1; FR3037393B1

Abstract

The invention relates to a device for weighing an object, said device comprising a rigid plate (21) that forms a dish for receiving the object (5) to be weighed, characterized in that the device further comprises a support (22) for supporting the rigid plate (21), said support (22) being in contact with a touch screen (41) of a terminal (4) in a contact region (42) and being suitable for characteristics of the contact region (42) to vary when the object (5) to be weighed is placed on the rigid plate (21).

Description

WEIGHTING DEVICE AND METHOD FOR TOUCH SCREEN TERMINAL

FIELD OF THE INVENTION

The present invention relates to the general technical field of weighing methods and devices. More specifically, the present invention relates to the field of weighing methods and devices for touchscreen electronic terminals.

In particular, the present invention relates to a method and a weighing device adapted to be integrated into a mobile terminal including a touch screen, such as a smartphone.

BACKGROUND OF THE INVENTION

Weighing machines have become more and more sophisticated and, in addition to weighing objects, they allow:

- the recording of the mass measured,

- the estimation of a fat level and / or a degree of hydration, etc.

This sophistication leads to a complexification of the control interface of such weighing devices which comprise more and more control buttons.

To solve this problem, we have already proposed:

to integrate wireless communication means in a weighing apparatus, and

- To deport the control interface to another device remote from the weighing device, such as a remote control.

The document FR 2 804 519 proposes in particular a solution for remotely controlling an electronic weighing device by means of a mobile terminal arranged for exchanging control data with the weighing apparatus.

A disadvantage of this solution is that it requires the use of two separate objects to measure a mass, namely the weighing device on the one hand and the mobile control terminal on the other hand. Furthermore, this solution does not allow to perform weighing operations in a mobility context.

An object of the present invention is to provide a device and a weighing method for overcoming at least one of the aforementioned drawbacks.

BRIEF DESCRIPTION OF THE INVENTION

For this purpose, the invention proposes a device for weighing an object, the device comprising a rigid plate constituting a plate intended to receive the object to be weighed, remarkable in that the device further comprises a support for supporting the plate rigid, the support being in contact with a touch screen of a terminal at a contact zone and being adapted so that a characteristic of the contact zone varies during the positioning of the object to be weighed on the rigid plate .

Preferred but non-limiting aspects of the device according to the invention are the following:

the device may comprise a computer adapted to estimate the mass of an object to be weighed, taking into account said characteristic variation of the contact zone;

the characteristic may be representative of the dimensions of the contact zone between the support and the touch screen;

the support may be a textured flexible material layer having a hardness of less than 80 Shore A;

the characteristic may be representative of a position of the contact zone between the support and the touch screen;

the support may comprise symmetrical first and second panels articulated about an axis in a crossing zone of said panels so as to define a deformable cross-member as a function of the mass of the object disposed on the rigid plate, at least the a section including a pad in contact with the touch screen at the contact area. The invention also relates to a method of weighing an object from a weighing device including a rigid plate constituting a plate and a plate support, characterized in that the method comprises the steps of:

- make a first measurement of a characteristic of the contact zone when the object is not on the rigid plate,

- make a second measurement of the characteristic when the object is on the rigid plate,

- estimate the mass of the object according to a variation between the first and second measurements.

Preferred but non-limiting aspects of the process according to the invention are the following:

the measured characteristic may be representative of an area of the contact zone between the support and the touch screen, the mass being estimated taking into account a Young's modulus of the support material in contact with the touch screen , the mass of the rigid plate and the first and second measurements;

the measured characteristic is representative of a position of the contact zone on the touch screen, the mass being estimated taking into account a coefficient of stiffness of a spring of the support, the mass of the rigid plate and the first and second measures.

The invention also relates to a hull for a mobile terminal including a device as described above.

The invention also relates to a computer program product including program code instructions recorded on a computer-readable medium, for carrying out the steps of the method according to one of the claims when said program is executed on a computer.

The invention also relates to a terminal including a device as described above and / or a computer program product as described above.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and characteristics of the device and the weighing method according to the invention will emerge more clearly from the following description of several alternative embodiments, given by way of non-limiting examples, from the attached drawings in which:

FIGS. 1 and 6 schematically illustrate a first variant embodiment of a weighing device,

FIG. 2 diagrammatically illustrates a second variant embodiment of the weighing device,

FIGS. 3a, 3b and 4 schematically illustrate a third variant embodiment of the weighing device,

FIG. 5 schematically illustrates steps of a weighing process,

FIG. 7 schematically illustrates curves representative of an estimated mass as a function of a displacement measured for tension and tension springs;

- Figure 8 schematically illustrates a fourth embodiment of the weighing device.

DETAILED DESCRIPTION OF THE INVENTION Various examples of methods and weighing devices according to the invention will now be described. In these different figures, the equivalent elements are designated by the same reference numeral.

The method and the weighing device are adaptable on any type of terminal 4 including:

processing means such as a processor and a memory programmed for the implementation of the weighing method,

- A touch screen for cooperating with the weighing device.

The terminal 4 is for example a mobile phone type Smartphone, an electronic tablet (such as an IPAD®), a personal assistant (or "PDA", acronym of the English expression "Personal Digital Assistant"), or any other type of fixed or mobile terminal known to those skilled in the art including a touch screen and processing means.

In the following, the device and the weighing method will be described in association with a mobile terminal 4 of the smartphone type.

1. Weighing device

1.1. General principles

Different embodiments of the weighing device can be envisaged. Advantageously, each of these modes can be integrated into a rigid shell for a mobile terminal 4. This makes it possible to obtain a shell having a dual function of protecting the touch screen 41 of the mobile terminal 4 and weighing objects.

With reference to FIGS. 1 and 2, the rigid shell may be composed of a half-shell forming a bottom 1 intended to cover the rear face of the mobile terminal 4, and of a half-shell forming a cover 2 intended to cover the front face mobile terminal 4.

In this case, the two half-shells 1, 2 can be pivotally mounted about an axis of rotation A-A 'extending along one of their respective edges. More specifically, the two half-shells 1, 2 can be connected by a link allowing their relative displacement in rotation with respect to each other between:

an open position in which the touch screen 41 of the mobile terminal 4 is accessible, and

a closed position in which the touch screen 41 is covered by the half-shell forming the cover 2.

The half-shell forming bottom 1 may comprise a substantially flat wall 11 including one or more flanges 12 at its periphery, the (or) flange (s) 12 extending perpendicularly to the plate 11 to define a receiving volume of the terminal 4. Advantageously, the dimensions of the reception volume may be slightly less than or equal to the dimensions of the mobile terminal 4 so as to ensure intimate contact:

the plate 11 on the rear face of the mobile terminal 4, and

flanges 12 on the lateral faces of the mobile terminal 4. The half-shell forming bottom 1 can be made of an elastic material, for example thermoplastic polyurethane (or "TPU" acronym of the English expression "Thermoplastic polyurethane") and / or silicone. This makes it possible to deform the flange (s) 12 to facilitate the insertion of the mobile terminal 4 into the reception volume. Once the terminal 4 housed in the reception volume, it is clamped by the flange (s) 12 by resilient return effect (s) of (or) flange (s) 12. This ensures a maintenance in position of the terminal 4 in the half-shell forming bottom 1.

The half-cover shell 2 may comprise a rigid plate 21 and a support 22 extending between the rigid plate 21 and the touch screen 41. The rigid plate 21 constitutes a scale plate to allow the weighing of object 5 to Using the mobile terminal 4. The support 22 is intended to be in contact with the touch screen 41 in a contact zone 42 to allow the implementation of a weighing operation.

This contact zone 42 may consist of one (or more) point (s) of contact or a contact surface. Advantageously, the contact zone is covered with a layer of electrically conductive material, such as an electrically conductive polycarbonate film. This conductive material is electrically connected, via the half-shells 1 and 2, to the electrical ground of the smartphone, or to an adequate electrical potential delivered by the connectors of the smartphone, to ensure the detection of the position of the contact by the touch interface in the case of a capacitive interface. As will be described in more detail below, the weighing of an object 5 is determined taking into account a measurement variation of the contact zone 42 between:

a measurement of the "empty" contact zone 42 where the rigid plate 21 has no object to weigh 5, and

a measurement of the "charged" contact zone where an object to be weighed is placed on the rigid plate 21.

This variation of measurement can consist of a variation of position of the contact zone or a variation of the contact surface. 1.2. First embodiment With reference to FIG. 1, a first embodiment of the weighing device is illustrated in which a variation of position of the contact zone 42 is considered for estimating the mass of an object 5.

The support 22 is a telescopic extensible support movable between:

a retracted position where the support 22 is folded over the rigid plate 21 of the half-shell forming a cover 2, and

- An extended position in which the support 22 is clear of the rigid plate 21 to allow the implementation of a weighing operation.

The support 22 comprises symmetrical first and second panels 221, 222 articulated about an axis BB '(parallel to the axis A-A') at a crossing zone at half length of said panels 221, 222 so as to define a deformable spider between the touch screen 41 and the rigid plate 21 defining the scale plate.

The ends of the first panel 221 are pivotally mounted about axes A-A 'respectively on the half-shell forming bottom 1 on the one hand and the rigid plate 21 on the other.

The ends of the second pan 222 are held free and each comprise a respective pivot pad, a first pad being intended to come into contact with the touch screen 41 and a second pad being intended to come into contact with the rigid plate 21. Alternatively, the end including the second pad may be slidably mounted on the rigid plate 21.

The support 22 also comprises a tension spring 223 extending between the first and second panels 221, 222. Advantageously, the spring 223 can be moved along the first and second panels 221, 222 to allow the mass range to be widened. measurable using the weighing device.

For example, for masses to be weighed low, the spring will be moved to a position closer to the crossing area of the first and second panels than for large masses to weigh.

In some embodiments, the tension spring 223 may be replaced by a torsion spring housed at the level of the crossing zone between the first and second panels 221, 222 around the axis B-B '. In this first embodiment, the contact zone 42 between the support 22 and the touch screen 41 is defined by the contact surface of the first pad on the touch screen 41.

The operating principle of this first embodiment of the weighing device can be as follows.

In a first step, a user of the mobile terminal 4 rotates the half-shell shell 2 relative to the half-shell forming bottom 1 to access the touch screen 41 of the mobile terminal 4.

The user selects a weighing function of an object in a menu displayed on the touch screen 41 of his mobile terminal 4.

The user then deploys the support 22 of the half-shell forming cover 2. It has the first pad presses on the touch screen 41. It also has the second pad presses on the rigid plate 21 constituting the scale plate intended to receive the object to be weighed 5. Finally, it moves the tension spring 223 in a desired position according to a weight range of the object to be weighed (for example "light" for objects whose mass is included between 0 to 50 grams, "heavy" for objects whose mass is between 50 and 300 grams, and "very heavy" for objects whose weight is between 300 grams and 1 kilogram).

Acquisition means of the touch screen 41 detect the position of the pad thereon.

The user then places the object to be weighed 5 on the rigid plate 21 constituting the scale plate. Under the effect of gravity, the mass of the object induces the application of a bearing force on the plate 21 tending to move it to the mobile terminal 4. This induces the movement of the first pad to the touch screen surface 41.

The variation of position of the first pad between:

the position of the first pad on the touch screen 41 when the object to be weighed is not disposed on the rigid plate 21, and

the position of the first pad on the touch screen 41 when the object to be weighed 5 is placed on the rigid plate 21,

then allows to estimate the mass of the object to be weighed 5, as will be described in more detail below with reference to the weighing method. Advantageously, vibration generating means of the mobile terminal 4 can be activated following the introduction of the object to be weighed so as to cancel the friction forces between the first (and / or second) pad and the touch screen 41 (respectively the rigid plate 21).

In addition, a calibration step can be implemented prior to the deposition of the object to be weighed on the rigid plate 21. To implement the calibration step, a reference object whose mass is known can be arranged on the rigid plate 21, prior to the step of depositing the object to be weighed 5. In this case, the estimation of the mass of the object to be weighed is performed taking into account the variation of position of the first pad between:

the position of the first pad on the touch screen 41 when the reference object is placed on the rigid plate 21, and

- The position of the first pad on the touch screen 41 when the object to be weighed 5 is disposed on the rigid plate 21.

Advantageously, the reference object whose mass is known may consist of the mobile terminal 4 itself.

In this case, once the support 22 deployed, the terminal 4 is arranged "face down" by placing the rigid plate 21 on a base such as a horizontal table, the touch screen 41 being opposite the base.

1.3. Second embodiment

Referring to Figure 2, there is illustrated a second embodiment of the weighing device. The weighing device comprises two half-shells 1, 2 respectively forming bottom and cover connected by a flexible joint 3 allowing their relative displacement of one relative to the other without constraint in a range of adequate clearance.

In this embodiment, the support 22 is composed of a layer of textured flexible material. Advantageously, the textured material may be partially or completely covered with a layer of electrically conductive material, such as an electrically conductive polycarbonate film. This conductive material is electrically connected, via the half-shells 1 and 2, to the electrical ground of the smartphone, or to a suitable electrical potential delivered by the connectors of the smartphone, to ensure the detection of contact by the touch interface in the case of a capacitive interface.

In the context of the present invention, the term "flexible material" is intended to mean a material whose hardness is less than 80 Shore A.

The textured layer is for example composed of a plurality of elements 224 projecting outwardly such as:

- spheres or portions of sphere,

cones whose tips are intended to come into contact with the touch screen,

cone trunks whose smaller bases are furthest removed from the rigid plate and are intended to come into contact with the touch screen,

- pyramids with triangular bases, pyramids with rectangular bases, etc.

In this case, the estimate of the mass of an object 5 is a function of a variation of the area of the contact surface of the elements 224 between a state of no load and a state of load of the weighing device.

More precisely in this second embodiment, when an object to be weighed is disposed on the rigid plate 21, the pressure applied to the rigid plate 21 increases. This induces an increase in the area of the contact zone 42 between the textured flexible material and the touch screen 41. It is then possible to determine the number of pixels of the flexible material in contact with the screen 41 by using the capacitive interface of the touch screen 41.

It is thus estimated the weight of the object to be weighed taking into account the variation of the area of the contact zone 42 between:

the area of the contact zone of the flexible material on the touch screen 41 when the object to be weighed is not disposed on the rigid plate 21, and

- The area of the contact area of the flexible material on the touch screen 41 when the object to be weighed 5 is disposed on the rigid plate 21.

As in the first embodiment, the calibration can be implemented using the mobile terminal 4 "face down" so that it is the terminal 4 itself which constitutes the reference object of known mass. 1.4. Third embodiment

Referring to Figures 3a, 3b and 4, there is illustrated a third embodiment of the weighing device. The weighing device comprises two half-shells 1, 2 respectively forming bottom and cover connected by a flexible joint 3 allowing their relative displacement of one relative to the other without constraint in a range of adequate clearance.

The inner face of the half-shell forming a cover (i.e. side facing the touch screen in the closed position) comprises a base 81 substantially flat and non-zero thickness. The base 81 comprises a layer of electrically conductive material on its face intended to come opposite the touch screen of the weighing device. This layer of electrically conductive material is advantageously connected to the ground of the mobile terminal via the hinge 3 and the half-shell forming bottom, these being constituted (or covered) with an electrically conductive material.

The base 81 comprises two housings each intended to cooperate with a respective blade 84 made of an electrically conductive elastic material. Each housing comprises first and second pairs of recesses 82, 83 extending longitudinally.

Preferably, the blades 84 are removable. The first pair of recesses 82 - said active recesses - is intended to receive a respective lateral edge of a flexible blade 84 when the user wishes to weigh an article (Figure 3a). The second pair of recesses 83 - said passive recesses - is intended to receive a respective lateral edge of the flexible blade 84 when the user does not wish to weigh an article (Figure 3b).

As illustrated in FIG. 3a, the width of the flexible blade 84 is greater than the distance between the active recesses 82 with which it is associated, so as to induce the buckling of the flexible blade 84 when its lateral edges are inserted in the recesses. assets 82. As illustrated in FIG. 3b, the width of the flexible blade 84 is substantially equal to the distance between the passive recesses 83 to which it is associated, so that the flexible blade 84 extends substantially in a plane when its lateral edges are inserted in the passive recesses 83. This limits the size of the device when the weighing function is not used.

The operating principle of this third embodiment of the weighing device can be as follows.

For each elastic blade 84, the user of the mobile terminal 4 releases it from its associated passive setbacks 83 (FIG. 3b) and engages it in its associated active recesses 82 to flare up the thus flexibly constrained blade (FIG. 3a).

The user then selects a weighing function of an object in a menu displayed on the touch screen 41 of his mobile terminal 4, and then positions the plate 21 of the half-shell forming a cover on the touch screen ( Figure 3a).

When an object to be weighed 5 is placed on the rigid plate 21 of the half-shell forming a cover, the pressure applied on the rigid plate 21 increases. This induces an increase in the area of the contact zone 85 between the elastic strips 84 and the touch screen 41 (FIG. 4). It is then possible to determine the mass of the object 5 taking into account a variation of the area of the contact zones 85 between the blades 84 and the touch screen 41 when the rigid plate 21 is "empty" and when the rigid plate 21 is "loaded" with an object 5 to be weighed.

Thus, the mass of an object 5 can be determined taking into account the variation of the area of the contact zones 85 between the blades 84 and the touch screen 41.

As a variant, the mass can be weighed taking into account a variation in the position of the center of gravity of the detected contact zones 85.

For example, in one embodiment, each blade 84 may be partially covered with one (or more) pattern (s) - such as a triangle - of electrically insulating material (if the blades are electrically conductive over their entire surface; Conversely, if the blades are electrically insulating, they may be covered with a pattern - such as a triangle - of electrically conductive material. In this case, a variation of the area of the contact zone by application of an object to be weighed induces a displacement of the barycentre of the detected contact zones 85. The measurement of this displacement makes it possible to deduce therefrom the mass of the object to be weighed 5.

The weighing method according to the invention will now be described in more detail. This weighing method can be programmed in the mobile terminal 4. More precisely, the weighing method can be stored in a memory of the mobile terminal 4 in the form of programming code instructions intended to be executed by a computer of the mobile terminal 4. , such as a processor (s), a microcontroller (s), a specific integrated circuit (s), or any other type of calculator known to man of career.

2. Weighing process

With reference to FIG. 5, the various steps of the weighing method are illustrated in the case where a reference product of known mass is used to calibrate the weighing device.

When the reference object has been put in place on the rigid plate, the method comprises a first step 60 of measuring a characteristic of the contact zone 42 between the support 22 and the screen 41.

In the case of the first embodiment of the weighing device, the first measuring step consists of measuring the position of the first pad on the touch screen.

In the case of the second embodiment of the device, the first measuring step consists in measuring the surface of the contact zone between the flexible material and the touch screen.

Once the first measurement step has been performed, the terminal can emit a visual, audible or tactile stimulus (step 61) to indicate to the user that the object to be weighed can be positioned on the rigid plate.

When the object to be weighed has been positioned on the rigid plate, the method comprises a second step 62 for measuring the characteristic of the contact zone 42 between the support 22 and the screen 41. In the case of the first embodiment of the device, the second measuring step consists of measuring the position of the first pad on the touch screen. In the case of the second embodiment, the second measuring step consists in measuring the surface of the contact zone between the flexible material and the touch screen.

Once the second measurement step has been performed, the terminal can emit a stimulus (step 63).

One or the other of the formulas described below is then applied to estimate the mass of the product to be weighed (step 64). 2.1. First embodiment of the device

With reference to FIG. 6, the principle of the step of estimating the mass of the product to be weighed is illustrated in the case of a weighing device according to the first embodiment.

Let E be the total potential energy of the system, it is written:

1

E = (m + m _v ) g + -k (l- _1Q ) ²

OR :

- m is the mass of the object to be weighed,

- m _p is the mass of the plate (to simplify the present demonstration, we neglect the mass of the support, being understood that this one could just as well be taken into account),

- the acceleration of terrestrial gravity,

- the altitude of the plateau,

- the stiffness of the spring,

I (l ₀ ) the length (empty).

The length of the spring "/" is a function of the horizontal position x of the movable fulcrum:

I - and, Where a is a geometric factor related to the anchorage point of the spring on the X-shaped structure (ratio of the distance from the anchor point to the central pivot at the distance from the movable fulcrum to the central pivot in the diagram given as an example ).

The altitude z and the horizontal position x are connected by the theorem of Pythagoras:

L ^l = x ^£ + z ^£

Where "L" is the length of an arm of the X structure.

We can therefore express the total potential energy of the system £ as a function of the horizontal position x:

I 1

E = (m _p + m ^ jg L ¹ - x ¹ + - k ^z (x- x ₀₎ ^z

For a given mass, the energy is minimal for the variations of x, we deduce:

ku ^z (x - ₀ ) L - x ²

m = iii _p

If the mass m _x of the X-structure and that m ,, of the spring are not negligible, they are added to the mass m _p of the plate with a geometric pre-factor which depends on the exact configuration of the assembly.

In the case of the schema given as an example, we would have m _p → m _v + ^ m _x +

1

(- + a) m _r .

It is therefore possible to connect the position of the measured pad x to the mass m to be determined. Figure 7 gives the form of m (x) for two types of spring:

a spring in tension (curve referenced 72), and

a torsion spring (curve referenced 71).

As the reader will have noted, there is a maximum allowable mass, any larger mass completely flattening the X structure. Four coefficients are needed for a calibration. The coefficients L and m _p can be manufacturer data (one can also measure L by completely flattening the structure in X), then a two-point calibration (empty then with the mass of the mobile terminal for example) can find the values numerals of x ₀ and ka ² / g.

If we replace the spring in tension by a torsion spring (return torque at the central pivot point), then the formula for calculating m as a function of x is written: m = - [sin ^{~ 1} (x / L ) - sin ^"1 (*" / £)] - m _p

3 Four coefficients are needed again for a calibration.

2.2. Second embodiment of the device

In the following, we will present a calculation formula for the second embodiment of the weighing device and more specifically in the case of a textured flexible material layer in which the projecting elements are spherical.

If we consider a deformable ball in contact with an infinitely rigid plane surface, the contact area between the ball and the plane is given by the Hertz contact formula:

Or :

F is the support force, D the diameter of the undeformed ball, and

E ^* = - with £ the Young's modulus of the material of the ball, and v its coefficient iv ²

of fish.

The total force due to the mass of the object m and the plateau m _v is F = (m + m _p ) g (with g the acceleration of the Earth's gravity).

It is distributed over N points of contact between the plate and the screen, so the formula connecting the mass to measure m to the total contact area A = Na is: 8E ^* A ^3/2

m = - m _n

3π ³ ¾ VÏV ^p

It is therefore possible to connect the measured contact area A to the mass m of an object to be weighed.

A calibration (unladen then with the mass of the smartphone for example) makes it possible to find the numerical values of m _p and the pre-factor of the term in A ^{3 / I.}

Note that the nonlinear shape extends the measurement range by degrading the accuracy for large mass objects.

If the projecting elements are not spherical in shape, or if they are not comparable to an elastic solid (bubble mat for example), the formula above does not apply and it will be necessary to perform an explicit calibration of the dependence curve of m as a function of A.

Thus, the device and the weighing method described above enable a user to estimate the mass of an object to be weighed with a precision of between one per thousand and one percent, this mass being able to vary between one tenth of a gram. and a few kilograms.

The reader will have understood that many modifications can be made to the invention described above without physically going out of the new teachings and advantages described herein.

For example, with reference to FIG. 8, a variant of the first embodiment illustrated in FIG. 1 is illustrated. In this variant, the mobile terminal is arranged vertically. This makes it possible to prevent the mass of the object to be weighed from being supported by the touch screen.

Therefore, all such modifications are intended to be incorporated within the scope of the appended claims.

Claims

Device for weighing an object, the device comprising a rigid plate (21) constituting a plate for receiving the object to be weighed (5), characterized in that the device further comprises a support (22) for supporting the plate rigid (21), the support (22) being in contact with a touch screen (41) of a terminal (4) at a contact zone (42) and being adapted so that a characteristic of the contact (42) varies when positioning the object to be weighed (5) on the rigid plate (21).

Weighing apparatus according to claim 1, wherein a computer is adapted to estimate the mass of an object to be weighed taking into account said characteristic variation of the contact area (42).

A weighing device according to any of claims 1 or 2, wherein the characteristic is representative of the dimensions of the contact area (42) between the support (22) and the touch screen (41).

Weighing device according to claim 3, wherein the support (22) is a textured flexible material layer having a hardness of less than 80 Shore A.

A weighing device according to any one of claims 1 or 2, wherein the characteristic is representative of a position of the contact area (42) between the support (22) and the touch screen (41).

Weighing device according to claim 5, wherein the support (22) comprises symmetrical first and second panels (221, 222) hinged about an axis (Β-Β ') at a crossing zone of said panels (221, 222). ) so as to define a deformable cross depending on the mass of the object (5) disposed on the rigid plate (21), at least one of the panels (221, 222) including a pad in contact with the screen touch (41) at the contact area (42).

7. Protective shell (2) for terminal (4) characterized in that it comprises a weighing device according to one of claims 1 to 6.

Method for weighing an object from a weighing device according to one of Claims 1 to 6, including a rigid plate (21) constituting a plate and a plate support (22), characterized in that the method comprises the steps of:

performing a first measurement (60) of a characteristic of the contact zone (42) when the object (5) is not on the rigid plate (21),

performing a second measurement (62) of the characteristic when the object (5) is on the rigid plate (21),

estimating (63) the mass of the object as a function of a variation between the first and second measurements.

A method according to claim 8, wherein the measured characteristic is representative of an area of the contact area (42) between the support (22) and the touch screen (41), the mass being estimated taking into account a Young's modulus of the support material (22) in contact with the touch screen (41), the mass of the rigid plate (21) and the first and second measurements.

10. The method of claim 8, wherein the measured characteristic is representative of a position of the contact zone (42) on the touch screen (41), the mass being estimated taking into account a coefficient of stiffness d a spring (223) of the support (22), the mass of the rigid plate (21) and the first and second measurements.

A computer program product including program code instructions recorded on a computer readable medium, for implementing the steps of the method according to one of the preceding claims when said program is executed on a computer.