FR2740216A1 - Water meter with optical reading device - Google Patents

Abstract

The meter (10) includes a device (18) which determines the volume of water measured by an axial turbine (12) actuating a mechanical counter (16). An LED (20) generates IR beams which are directed towards the surface (26a) of the counter roller. Silicon photodiodes (22,26) detect the light reflected by the roller surface. The roller presents a number of angular sectors (28) placed on its surface along a circle centred on the rotation axis (17). A fix marker (30) is placed opposite the roller surface. The marker is a window provided in the exterior wall of the counter.

Description

The invention relates to a device for counting a physical quantity comprising a device for determining the physical quantity measured by said counting apparatus and to a method for determining the physical quantity measured by the counting apparatus.

To determine, for example for billing purposes, the physical quantity measured by a counting apparatus provided with a rotating element associated with said apparatus, such as a mechanical totalizer roll and whose angular position with respect to a fixed reference is representative of the measured quantity, it is sufficient to read the numbers written on said rollers.

However, the simple reading of these rollers is not always easy considering, in particular, the accessibility of metering devices to people who make the visual survey of physical quantities (quantities of water, gas or electricity) measured. This can lead to read errors when metering devices are placed in confined spaces, or even prevent playback when subscribers with installed devices are absent during the survey.

Also, more and more frequently, we seek to know the physical quantity measured by counting devices without having to make a visual survey.

However, in order to determine this measured physical quantity, it is necessary to be able to reliably know the angular position e of one (or more) roll (s) of the totalizer or, more generally, the angular position of less a rotating element associated with the counting apparatus and which is representative of the measured physical quantity.

Various devices are known capable of identifying the angular position of a totalizer roll and, for example, EP 0 124 434 which proposes to use a bar code to identify each angular position of a totalizer roll and then read, by means of an optical reader, the bar code corresponding to the angular position O of said roll.

Such devices are rarely simple to implement and require in particular the use of sophisticated equipment for reading the rollers.

The present invention aims at remedying the disadvantages of the prior art by proposing a device for counting a physical quantity comprising a device that makes it possible to determine, in a simple manner, the physical quantity measured by said counting device from at least one rotating element associated with the counting apparatus and whose angular position with respect to a fixed reference is representative of said measured physical quantity.

The present invention thus relates to an apparatus for counting a physical quantity comprising a device for determining said physical quantity measured by the counting apparatus from at least one rotating element associated with said apparatus and whose angular position O relative to a fixed reference is representative of the measured physical quantity, characterized in that said device comprises means for emitting an electromagnetic radiation consisting of several beams in the direction of a face of the rotating element, said rotating element comprising on said face a marking having an attenuation of the electromagnetic radiation varying with the angular position O of the rotating element relative to the fixed reference, according to a known law y (O) which is represented by a two-part curve whose first part comprises a first direction of variation and whose second part has a second direction of variation opposite in the first direction of variation, the device also comprising: means for receiving two beams attenuated by the marking and extraction for said beams of the two values y (01-0) and y (O2-O) of the attenuation corresponding to the electromagnetic radiation, where O1 and O2 are the various fixed and known angular positions relative to the fixed reference of said reception means, and means for deriving from the y (O) law, two values y (O1- O) and y (O2-O) and angular positions 01, 2 of said receiving means, the angular position O of the rotating element and therefore the physical magnitude.

According to a preferred feature of the invention, the face of the rotating element comprises a so-called reference zone having an attenuation value of the electromagnetic radiation independent of the attenuation law y (O) and serving as a reference, said device further comprising: - additional reception means of a third beam attenuated by the reference area and extraction of said beam with a so-called reference attenuation value, said additional reception means being in an angular position 03 , fixed and known relative to the fixed reference, - and means for deriving from the law y (O), the three attenuation values and the angular positions o 2, O3 of the receiving means, the angular position O of the rotating element and therefore the physical magnitude.

These additional reception means make it possible to standardize the signals that are received by the main reception means, that is to say to make them essentially proportional to the attenuation value of the marking and not to a parasitic attenuation value. .

This makes it possible to obtain the angular position O of the rotating element with more precision.

The first part of the curve representative of the attenuation law y (O) is for example increasing and the second part of the curve is decreasing.

The term ascending (resp., Decreasing) must be interpreted according to the mathematical meaning and therefore means in the present context not strictly increasing (or decreasing). It is therefore a curve which does not decrease (or which does not increase).

The first part of the curve can however be decreasing and the second part of the curve is then increasing.

According to one embodiment of the invention, the attenuation of the electromagnetic radiation varies discontinuously from an angular position of the rotating element to another consecutive angular position.

The face of the rotating element may comprise a plurality of angular sectors, each of which has a different marking attenuation value.

The receiving means can then be placed relative to one another at an angular deviation greater than the angular distance of the angular sectors and therefore the values y (O1-O) and y (O2-o) may be different. one from the other.

As a variant, the receiving means may also be placed relative to one another at an angular distance smaller than the angular distance of the angular sectors and therefore the values y (O1-O) and y (O2- O) are substantially always the same.

According to another embodiment, the attenuation of the electromagnetic radiation can vary continuously from an angular position of the rotating element to another consecutive angular position.

Preferably, the electromagnetic radiation is of the optical type.

However, the electromagnetic radiation could for example be a magnetic field.

Preferably, the face of the rotating element attenuates the beams of optical radiation by transmission along a dimension perpendicular to the face of said rotating element and called thickness.

The value of the optical transmission specific to each surface element of the face of the rotating element is substantially the same throughout the thickness of said element.

According to one variant, the value of the optical transmission may vary according to the thickness of the rotating element.

 It should be noted that instead of attenuating beams of optical transmission radiation, they could be attenuated by reflection.

The rotating element is for example a roll of a mechanical totalizer which is associated with the counting apparatus.

This rotating element could also be a disc directly connected to the axis of a measuring member of the counting apparatus.

The present invention also relates to a method for determining a physical quantity measured by a counting apparatus from at least one rotating element associated with said apparatus and whose angular position O with respect to a fixed reference is representative of the measured physical quantity, characterized in that it consists in: - emitting electromagnetic radiation consisting of a plurality of beams in the direction of one face of the rotating element, - attenuating at least two beams of said radiation in a characteristic manner of the angular position O of the rotating element according to a known law y (O) which is represented by a two-part curve whose first part comprises a first direction of variation and whose second part comprises a second direction of variation opposite to the first direction of variation, - receiving said attenuated beams in two different angular positions 01, 02, fixed and known relative to the fixed reference, - extracting from the amount of radiation of each received beam the attenuation values y (O1-O) and y (O2-0) characteristic of the angular position O of the rotating element and the respective angular positions O1 and O2, - deduce of the law y (O), of the two values y (O1-O), y (O2-o) and of the angular positions O1 and O2, the angular position 0 of the rotating element and therefore the physical quantity.

According to a preferred feature, the method further comprises: attenuating at least one beam of said radiation independently of the attenuation law y (0); receiving said attenuated beam in a known and fixed angular position O3 relative to the fixed reference, - extracting from the amount of radiation of said attenuated beam the so-called reference attenuation value, - deducing from the attenuation law, attenuation values y (O1-O), y (02 0), the reference attenuation value and the angular positions o 2 and 03, the angular position O of the rotating element and therefore the physical quantity.

According to other preferred features of the invention - the first part of the curve representative of the attenuation law y (O) is increasing and the second part of the curve is decreasing.

the first part of the curve can be decreasing and the second part of the curve is then increasing.

The attenuation of the electromagnetic radiation varies discontinuously from an angular position of the rotating element to another consecutive angular position.

The attenuation of the electromagnetic radiation varies continuously from an angular position of the rotating element to another consecutive angular position.

the attenuation values y (OI-O) and y (O2-O) are substantially identical.

the attenuation values y (O 1 -O) and y (O 2 -O) are different from each other.

the electromagnetic radiation is of the optical type.

the beams of the optical radiation are attenuated by reflection on the face of the rotating element.

the beams of the optical radiation are attenuated by transmission through the face of the rotating element.

The invention finds a particularly advantageous application in the determination of a volume of fluid measured by a counting apparatus.

Other features and advantages will become apparent from the following description given solely by way of non-limiting example, and with reference to the accompanying drawings, in which: - Figure 1 is a schematic view of a metering apparatus of a physical quantity provided with a device according to one embodiment of the invention, - Figure 2a is a view of the device of Figure 1 according to the arrow A for a first position of the totalizer roller, - Figure 2b is a schematic partial perspective view of the totalizer roll, - Figure 2c illustrates the different angular positions 81 to O3 of the receiving means, - Figure 2d is a view of the device of Figure 1 according to the arrow A for a second position 3 represents the optical transmission attenuation law y (O) of the roll, FIG. 3a represents the optical transmission attenuation law y (O) of the roll according to a variant of FIG. 3b represents the optical transmission attenuation law y (O) of the roll according to another embodiment variant; FIG. 4 schematically represents an electronic block 34 for processing the signals delivered by the reception means of the device according to the invention, - Figure 5 shows in more detail a current-voltage converter block of the circuit of Figure 4.

As shown very schematically in FIG. 1, a counting apparatus 10 of known type, for example a water meter, comprises a measuring member 12 of the physical quantity which is a volume of water, a kinematic chain 14 , for example a gear train, which connects the measuring member to a mechanical totalizer of which a single roller 16 is marked in this figure. This roller 16 is rotatably mounted on an axis 17.

The water meter according to the invention comprises a device 18 for determining the volume of water measured by the measuring member 12 which may be, for example, an axial turbine or a rotary piston or a propeller.

The device 18 comprises emission means 20, an electromagnetic radiation consisting of several beams which are directed on a face 16a of the roller.

The electromagnetic radiation is preferably of the optical type and the chosen wavelengths are for example in the infrared radiation.

The device 18 also comprises means of reception 22, 24 of two beams of the optical radiation emitted by the emission means 20, as well as additional receiving means 26 of a third beam of the optical radiation.

The emitting means 20 consist, for example, of a light-emitting diode emitting infrared radiation of wavelength close to 900 nm and marketed by SIEMENS under the reference LD271.

The reception means 22 to 26 are, for example, constituted by receivers of the silicon photodiode type, sensitive to radiation of wavelength close to 900 nm and marketed by the company.
SIEMENS under the reference BPY63P.

The roll 16 comprises on the face 16a a plurality of angular sectors 28 distributed along a ring centered on the axis of rotation 17 (Fig2a).

These angular sectors, 10 in number, extend in a dimension perpendicular to the face 16a of the roller 16 which corresponds to the thickness of said roller.

Thus, the angular sectors also appear on the opposite face 16b of the roll.

A fixed marker 30 which is in fact a window formed in the outer wall of the totalizer is disposed opposite the roller and usually permits the visual reading of the water meter.

Figures ranging from 0 to 9 are inscribed on the perimeter 16c of the roller (Fig.1) so that an angular sector is associated with a number (Fig.2b).

During operation of the water meter, the roller 16 rotates about its axis 17 and occupies different successive angular positions relative to the mark 30 which are each representative of a volume of water measured by the meter.

Usually, the person performing the visual survey of the meter reads the number placed vis-à-vis the window 30 and which corresponds to a precise volume of water measured by the measuring member 12 of said counter.

To determine this volume of water without making a visual survey, it is necessary to know at a given moment the angular position of the roller, which amounts to identifying the angular sector which is arranged opposite the window 30.

To do this, a marking is provided on the roll 16 exhibiting an attenuation of the optical radiation which varies with the angular position O of said roll according to a known law y (O).

Each angular sector has a different marking attenuation value and, for example, is characterized by an optical transmission value of its own.

The receivers 22 and 24 occupy respective fixed angular positions O1 and O2, which are different from one another and are known with respect to the window 30. These receivers are arranged opposite the face 1 6b of the roll 16, and, more precisely, opposite the crown according to which the ten angular sectors are distributed.

The receivers 22, 24 are placed relative to one another at an angular spacing AO = 2-01 which is for example greater than the angular difference corresponding to the angular width of the angular sectors 28 (Figs.2a and 2d). ). For the sake of simplification e = oi = 0.

 It is also possible to provide that the attenuation of the optical radiation is carried out by reflection, each angular sector then being located solely on the face 16a of the roll and not according to the entire thickness of the roll and having a reflectivity of its own.

In this case, the means for receiving the beams from the optical radiation are then placed opposite the face 16a as the transmission means.

The roller 16 also comprises a so-called reference zone 32 which extends from the face 1 6a to the face 16b, over the entire thickness of said roller, and which is characterized by an optical transmission value that is independent of the law. attenuation y (O).

This reference zone 32 has the shape of a ring disposed inside the ring formed by the angular sectors 28 and centered on the axis 17.

The third receiver 26 is placed vis-à-vis the zone 32 in a fixed angular position O3 and known with respect to the window 30 (Figs 2a and 2c).

The attenuation law y (O) is represented by a two-part curve, the first of which has a first direction of variation and the second part of which has a second direction of variation opposite to the first.

For example, the first part of the curve is not strictly increasing and the second part is not strictly decreasing (Fig.3).

As shown in FIG. 3, the transmission attenuation of the optical radiation varies in a discontinuous manner from an angular position of the roll to another consecutive angular position.

In FIG. 3, the optical transmission values vary in fact by substantially regular jumps from t0 to t9, all 36, when the roll completes one complete revolution.

The transmission law y (O) is a periodic function and the same values are therefore repeated for rotations of the roll at an angle greater than 360 ".

The roller is for example made of transparent plastic, the transparency being variable along the angular sectors 28 and fixed in the reference zone 32.

The value of the constant optical transmission t10 in the reference zone 32 is for example greater than the values obtained for the transmission of each of the angular sectors.

Instead of the value of the optical transmission being the same over the entire thickness of the roll, it is possible, for example, to provide that the optical transmission varies according to the thickness. This can for example be obtained if the roll is of composite type, that is to say if it consists of several superimposed discs, each having ten angular sectors with variable optical transmission, and for which the values of the optical transmissions of two angular sectors placed vis-à-vis differ from each other.

This characteristic can also be applied to reference area 32.

According to a variant of the invention shown in FIG.
The attenuation of the optical radiation, for example by transmission, can vary continuously from one angular position of the roller to another consecutive angular position.

In addition, it is possible that the curve of the law of attenuation is not strictly decreasing in its first part and not strictly increasing in its second part (Fig.3b).

Similarly, the attenuation of the optical radiation may vary discontinuously from an angular position to another consecutive angular position according to a law whose representative curve is not strictly decreasing in its first part and not strictly increasing in its second part. This last variant is not shown in the figures.

The transmitting means 20 emit optical radiation consisting of several beams at a solid angle wide enough to cover the three receivers 22, 24 and 26 in their entirety.

The beams of the optical radiation pass through the angular sectors 28 which are, at this moment, opposite the receivers 22 and 24, as well as the part of the reference zone 32 which is opposite the receiver 26 and are attenuated. depending on the value of the optical transmission considered.

As shown in FIG. 2a, the receivers 22 and 24 respectively receive beams which have passed through the angular sectors of transmission values t4 and t3, these values t4 and t3 corresponding to the respective values y (O1-O), ie y (0 ), and y (O2-O).

The receiver 26 receives meanwhile a beam that has passed through the reference area 32 of transmission value t10.

Receivers 22 and 24 convert the amount of radiation, or energy, contained in the received beams into electrical signals representative of the optical attenuation experienced by each of said beams.

An electronic unit 34 for processing the electrical signals then makes it possible to extract from these signals the optical transmission values t4 and t3 and to deduce the angular position O of the roll 16, that is to say the volume of water measured, providing on the outputs of said block, four information bits to represent the ten possible angular positions of said roll, that is to say the ten figures indicated on the circumference 16c of the roll.

In practice, an attenuation law y (O) such as that represented in FIG. 3 is produced on the roll 16, the pair of corresponding values t 1, read by the receivers 22 and 24, are measured for each of the angular positions of the roll. and it is known that at each value ti corresponds a figure indicated on the perimeter 16c of said roll (FIG. 2b). The angular position of the receivers 22 and 24 relative to the fixed reference 30 is also known and it is known that the angular position of the roll is given, in this particular case (0 = 0 = 0), by the value of the optical transmission. obtained by the receiver 22.

Therefore, a prior calibration of the device makes it possible to integrate in the electronic block 34 a correspondence table which, at each pair of values read by the receivers 22 and 24, corresponds to an angular position of the roll, that is to say say a number indicating a volume of water measured by the meter.

However, depending on the angular positions O 1 and O 2 chosen with respect to the window 30, the value of the optical transmission identifying the angular position of the roller is not necessarily that corresponding to one of the receivers.

In a general manner, if V1 and V2 are the values respectively obtained by the receivers 22 and 24, it is agreed that, when Vt = t1 and V1> V2, then, the position of the roll is determined by the sector angular transmission value ti.

On the other hand, if V1 <V2 this corresponds to the case shown in FIG. 2d where the first receiver 22 identifies a transmission value t0 (point C of FIG. 3) and the second receiver 24 identifies a transmission value t9 (point D of Figure 3). In this case, it is agreed that the angular position of the roll is determined by the angular sector of transmission value t0.

If one of the optical beams crossing the roller 16 is astride between two angular sectors 28, that is to say in a discontinuity zone (FIG. 3), then the optical transmission value extracted from this beam will adopt an intermediate value between the two sectors concerned. In this case, to remove the indetermination, one or other of the two consecutive optical transmission values t0 to t9 which frame the intermediate value will be chosen.

Block 34 will be described in more detail later.

 It should be noted that knowledge of the transmission value obtained from a single receiver 22 or 24 is not sufficient to perfectly determine the angular position of the roll.

Indeed, as shown in FIG. 3, the representative curve of the law y (O) shows that for an extracted optical transmission value, for example, t4, there are two possible values of 0, OA but also the corresponding value at A ', or 3600, and so there is uncertainty.

The same remark applies to the receiver 24.

Each of the receivers 22 or 24 taken in isolation therefore does not make it possible to precisely determine the angular position of the roller 16.

However, when using two receivers that are angularly offset, this uncertainty can be removed.

This is apparent from FIG. 3, where two possible values of 0, respectively, appear for each optical transmission value.
OA and 3600 (A '), OB and 360 (B').

Since the receivers are angularly offset, the position associated with the points A 'and B' can be rejected since it corresponds to a single angular position.

The knowledge of the transmission value t10 associated with the receiver 26 makes it possible to serve as a reference for the determination of the transmission values seen by the receivers 22 and 24. In fact, these latter values can be modified by a change in the transmission of the transmission. diode 20 or an opaque deposit on the roll such as dust or condensation.

These modifications are therefore also taken into account by the receiver 26 and, by dividing, for example, the transmission values associated respectively with the receivers 22 and 24 by the transmission value t10, it is possible to determine the angular position of the roll with a larger accuracy and better reliability.

FIG. 4 represents the structure of the electronic signal processing unit 34 making it possible to determine the angular position of the roll 16 from the quantities of radiation measured by the receivers 22, 24 and 26.

This circuit comprises a multiplexer 36, a voltage converter IN 38, an analog digital converter 40 and a logic block 42 which is in fact a read-only memory ROM (Read Only
Memory) containing the various instructions for carrying out the method according to the invented logic value received from the block 42, this multiplexer sends to the converter IN one or the other of the currents of the receivers.

FIG. 5 details the converter IN 38 which is a simple operational amplifier 44, for example of the TLC271 type of Texas
Instruments, in transimpedance assembly using a resistor R. The converter IN converts the current from the receiver selected by the logic block into voltage and transmits this voltage to the A / D converter 40 which transforms it into a 4-bit binary word and to the logic block 42 The logic block can therefore transform in binary form the currents of the receivers 22, 24 and 26.

To determine the position of the roller 16, the logic block 42 evaluates the amounts of radiation received by the receivers by transforming into binary value each current value 11, 12, 13 of the respective receivers 22, 24 and 26 extracts from these binary values the values transmissions seen by the first and second beams forming ratios vu = 11/13 and v2 = 12/13, then uses the method described above to deduce the angular position of the roller 16.

In practice, a simple comparison of these values V1 and V2 with the correspondence table makes it possible to deduce the angular position of the roll and therefore the volume of water measured.

The invention therefore makes it possible with a small number of elements to determine in a simple and reliable way the angular position of a counter of counter totalizer. It is of course possible to apply the device according to the invention to each roller of a counting device totalizer to obtain, in the form of binary-shaped electrical signals, the indication of the physical quantity measured by the counter, in order to for example, to transmit it remotely.

 It should be noted that it is also possible to emit in the direction of the face of the rotating element radiation of radioactive particles consisting of several beams. The rotating element comprises for example a plurality of angular sectors made of lead and having a variable thickness depending on the angular position of said rotating element, thus varyingly attenuating the radiation of radioactive particles.

The means for receiving the beams of radioactive particles attenuated by the rotating element are formed by radioactive particle counters which make it possible to obtain the corresponding attenuation values.

As a further example, it is possible to emit in the direction of the face of the rotating element magnetic radiation created for example by a coil traversed by an electric current.

The rotating element comprises for example a plurality of angular sectors made of mumetal and having a variable thickness as a function of the angular position of said rotating element, thereby varying the magnetic radiation.

The receiving means are for example formed by Hall effect sensors.

All that has been said previously for the determination of the angular position of the rotating element and therefore the volume measured by the counter remains valid for these two examples and will not be repeated.

Claims (33)

1. Apparatus for counting (10) a physical quantity comprising  a device (18) for determining said physical quantity  measured by the counting apparatus from at least one  rotating element (16) associated with said apparatus and whose position  angle O relative to a fixed landmark (30) is representative of  the measured physical quantity, characterized in that said device  comprises means (20) for transmitting radiation  electromagnetic consisting of several beams in the direction  a face (16a) of the rotating element, said rotating element (16)  having on said face a marking having a  attenuation of the electromagnetic radiation varying with the  angular position O of the rotating element relative to the reference  fixed, according to a known law y (O) which is represented by a curve  in two parts, the first part of which has a first meaning  of variation and of which the second part has a second meaning of  variation opposite the first direction of variation, the device (18)  also including:  means for receiving (22, 24) two beams attenuated by  marking and extraction for said beams of both  y (O1-O) and y (O2-O) values of the corresponding attenuation of  electromagnetic radiation, where OI and O2 are the different  fixed and known angular positions relative to the fixed reference  (30) said receiving means,  and means (34) for deriving from the law y (O), two values y (O 1 -O) and y (O 2 -O) and angular positions O 1, o 2  said receiving means, the angular position e of the element  turning and therefore the physical size. 2. Apparatus according to claim 1, wherein the face (16a) of  the rotating element comprises a so-called reference zone (32)  having a radiation attenuation value  electromagnetic independent of the attenuation law y (O) and  serving as a reference, said device (18) comprising in  outraged:  - additional receiving means (26) of a third  beam attenuated by the reference area and extraction of this  beam of a so-called reference attenuation value, said  additional receiving means being in a position  angular 03, fixed and known with respect to the fixed reference (30),  - and means (34) to deduce from the law y (O), of the three  attenuation values and angular positions o 2, O3 of  receiving means, the angular position O of the rotating element  and therefore the physical size. Apparatus according to claim 1, wherein the first part  of the curve is increasing and the second part of the curve is  decreasing. Apparatus according to claim 1, wherein the first part  of the curve is decreasing and the second part of the curve is  growing. 5. Apparatus according to one of claims 1 to 4, wherein  the attenuation of electromagnetic radiation varies so  discontinuous of an angular position of the rotating element (16) to  another consecutive angular position. 6. Apparatus according to one of claims 1 to 4, wherein  the attenuation of electromagnetic radiation varies so  continuous from an angular position of the rotating member to (16) a  other consecutive angular position. Apparatus according to claim 5, wherein the face (16a) of  the rotating element (16) has a plurality of sectors  angular members (28) each having an attenuation value of  different marking. Apparatus according to claim 7, wherein the means of  reception (22, 24) are placed relative to each other following a  angular deviation (28) less than the angular difference of the sectors  angular values and therefore the values y (O1-O) and y (02-0) are substantially  the same. Apparatus according to claim 7, wherein the means of  reception (22, 24) are placed relative to each other following a  angular difference greater than the angular difference of the sectors  angular values (28) and therefore the values y (O1-O) and y (02-0) are  different from each other. 10. Apparatus according to one of claims 7 to 9, wherein the  angular sectors (28) are distributed on the face (16a) of  the rotating element (16) following a ring. Apparatus according to claims 2 and 10, wherein the zone of  reference (32) of the rotating element (16) is located inside  the crown. 12. Apparatus according to one of claims 1 to 11, wherein the  Electromagnetic radiation is of the optical type. Apparatus according to claim 12, wherein the face (16a) of  the rotating element (16) attenuates the beams of the radiation  optical reflection. Apparatus according to claim 12, wherein the face (16a) of  the rotating element (16) attenuates the beams of the radiation  optical transmission by a dimension perpendicular to  the face of said rotating element and called thickness. Apparatus according to claim 14, wherein the value of the  optical transmission specific to each surface element of the  face (16a) of the rotating member (16) is substantially the same  following the entire thickness of the rotating element. Apparatus according to claim 14, wherein the value of  optical transmission specific to each surface element of the  face (16a) of the rotating element (16) varies according to the thickness of  the rotating element. Apparatus according to claims 1 and 12, wherein the  transmission means (20) comprise a diode  emitting. Apparatus according to claims 1 and 12, wherein the  receiving means (22, 24) comprise two photodiodes. Apparatus according to claims 2 and 18, wherein the  additional receiving means (26) furthermore  a third photodiode. 20. Apparatus according to one of claims 1 to 19, wherein  the rotating element (16) is a roller of a totalizer associated with  the counting apparatus. Apparatus according to claim 20, comprising a device for  determining (18) the physical quantity measured by said  device for each roll of the totalizer. 22. Method for determining a physical quantity measured by  a counting apparatus (10) from at least one element  rotating (16) associated with said apparatus and whose angular position e  relative to a fixed landmark (30) is representative of the magnitude  measured physics, characterized in that it consists of  - emit electromagnetic radiation consisting of  several beams towards a face (16a) of the element  rotating (16),  - attenuate at least two beams of said radiation so  characteristic of the angular position O of the rotating element  following a known law y (O) which is represented by a curve in  two parts, the first part of which has a first meaning of  variation and the second part of which has a second meaning of  variation opposite to the first direction of variation,  - receive said attenuated beams in two angular positions  o 2 different, fixed and known with respect to the fixed reference (30),  - extracting the amount of radiation from each beam received  the attenuation values y (0) and y (02-o) characteristics of the  angular position 0 of the rotating element and positions  angular positions, respectively, and  - deduce from the law y (O), two values y (O1-O), y (O2-O) and  angular positions Ol and 02, the angular position O of the element  turning (16) and therefore the physical magnitude. The method of claim 22, further comprising:  - attenuate at least one beam of said radiation so  independent of the attenuation law y (O),  receiving said attenuated beam at an angular position O3  known and fixed with respect to the fixed reference (30),  extracting the amount of radiation of said attenuated beam  so-called reference attenuation value,  - deduce from the attenuation law, attenuation values y (014),  y (O2-O), reference attenuation value and positions  angular 01, o 2 and 03, the angular position O of the element  turning (16) and therefore the physical magnitude. 24. The method of claim 22, wherein the first  part of the curve is increasing and the second part of the curve  is decreasing. 25. The method of claim 22, wherein the first  part of the curve is decreasing and the second part of the  curve is increasing. 26. Process according to one of claims 22 to 25, according to which  the attenuation of electromagnetic radiation varies so  discontinuous of an angular position of the rotating element (16) to  another consecutive angular position. 27. Process according to one of claims 22 to 25, according to which  the attenuation of electromagnetic radiation varies so  continuous from an angular position of the rotating element (16) to a  other consecutive angular position. 28. The method of claim 26 wherein the values  attenuation values y (O1-O) and y (O2-O) are substantially identical. 29. The method of claim 26 or 27, wherein the  attenuation values y (Ol-O) and y (O2-O) are different one of  the other. 30. Process according to one of claims 22 to 29, wherein the  Electromagnetic radiation is of the optical type. 31. The method of claim 30, wherein the beams of the  optical radiation is attenuated by reflection on the face (16a)  of the rotating element (16). 32. The method of claim 30, wherein the beams of the  optical radiation are attenuated by transmission through the  face (16a) of the rotating element (16). 33. Application of the device according to one of claims 1 to 21 and  method according to one of claims 22 to 32 to  determination of a volume of fluid measured by a device of  counting (10).