FR2647544A1 - Device for measuring angles of inclination - Google Patents

Abstract

The invention relates to a device for measuring angles of inclination, including a sensor 10 and electronic measurement means 50, wherein the electronic measuring means 50 comprise: - electrical current measurement 51 and supply 52 means, and wherein the sensor comprises: . a first hollow conducting element 11, this element being divided at at least one of the planes of symmetry into two identical parts, electrically insulated from each other, each part being connected to the current measurement means 50; . a second conducting element 12 centered inside the first element 11, this element being connected to the supply means 52, and; . a conducting liquid 18 filling half the internal volume of the first element 11. Application to the measurement of angles.

Description

DEVICE FOR MEASURING TILT ANGLES
DESCRIPTION
The invention relates to a device for measuring angles of inclination and more particularly the production of a sensor of the incLinometer type and of its electronics. Such a sensor makes it possible to carry out measurements of angles and variations of angles.

 The simplest and oldest way to measure an angle is to use a spirit level coupled to a protractor. Other more sophisticated devices exist on the market.

We will quote for example the inclinometer-accelerometer
SENSOREX model 41100. FIG. 1 schematically shows such a device.

 In this inclinometer, the sensitive element is an unbalanced galvanometer 1 associated with an optical position detector 2. When the device is inclined by an angle X, the pendulum 3 tends to follow this inclination. Its position is detected and translated into a booster current injected into the galvanometer to bring it back to the equilibrium reference position. This recall current, proportional to the component of gravity detected, is measured across a precision resistor 4. Such a system is called "servo-controlled". This device makes it possible to obtain good precision in the measurements but at the cost of complex electronics.

It is also known a miniature inclinometer, under the name SPERRY, less expensive but less sophisticated since it is not controlled, this inclinometer is .egalcmcnt distributed by the company
SENSOREX. This device uses roughly the same principle as the previous one. When the sensor rotates around its sensiole axis, it provides a very linear variation in capacitance which is converted into an electrical voltage proportional to the angle of rotation.

 It is also known from US patent 3906471 a monoaxial inclinometer based on the principle of a capacitive measurement. This inclinometer consists of a first cylindrical part inside which are housed four other parts, all concentric. A liquid with a high dielectric constant moves as a function of the inclination in the crown formed by the internal parts with the external part. Its movement changes the capacity of an internal part with the surface of the corresponding external part.

 It is not possible with such an inclinometer to make measurements with respect to several axes.

- Most of all these devices currently known have the following general characteristics
- a narrow operating range: a few tens of degrees in one direction,
- an electronic-mechanical servo system for the sensor or a certain sensitivity to shocks and variations in climatic conditions,
- standard dimensions often too large for a good number of applications,
- for the most sensitive models: a relatively high price for the sensor.

 These features often make them difficult to use in many applications. Indeed, a good use of these sensors supposes that one knows with precision the axis of the angle to measurer or, if it is a dep 1 a cement, the axis of displacement.

 From the moment we contact these axes, it is then a question of orienting as precisely as possible. the sensitive axis of the sensor parallel to the axis along which the measurement must be made.

 This adjustment is not always possible and in the case where the sensor is not perfectly oriented, the measurements obtained may be vitiated by an error, of course harmful.

 The object of the invention therefore consists of a device for measuring angles of inclination which does not have the drawbacks which the known devices present.

The measuring device which is the subject of the invention comprises all of the following characteristics:
- an operating range widened to its maximum: around 1800 (+/- a few degrees) in all directions of space (along 3 axes),
- A simple design and which at the same time provides great strength because this device is made from a simple mechanical system. The impact resistance is then only linked to a manufacturing problem,
- a shape and a dimension of the modular sensor which can be adapted to the requirements of each user without harming the qualities of the measurement,
- dissociation between mechanics and processing electronics,
- a low manufacturing cost price (particularly with regard to the mechanical part allowing use in a "lost" sensor).

The invention more particularly relates to a device for measuring angles of inclination comprising a sensor and electronic measuring means characterized in that the electronic measuring means comprise
- means for measuring electric currents and supply and in that the sensor comprises
a first hollow conductive element comprising at least one plane of symmetry, this element being divided at this plane of symmetry into two identical parts, electrically isolated from each other, each part being connected to the current measurement means,
a second conductive element centered inside the first element and equidistant from the different parts, this element being connected to the supply means, and
a conductive liquid filling part of the interior volume of the first element so as to be in permanent contact with the second element.

 According to a characteristic of the invention, the measuring device comprises electrical insulation elements which make it possible to isolate the different parts constituting the first element.

 According to another characteristic of the invention, the measurement of the current is carried out using connection means fixed on each insulated part, these connection means make it possible to connect each insulated part to the measuring means.

 According to an exemplary embodiment according to the invention, the first hollow conductive element has an inner envelope of spherical shape and the second element is of spherical shape.

 Advantageously, the insulating elements consist of insulating plates cut so as to have a hollowed out shape corresponding substantially to that of the first element, at least one of these plates comprising a tab whose end holds the second element and on which is locates an insulated conductor connecting this element to the supply means.

 According to another exemplary embodiment in accordance with the invention, the first hollow conductive element has a cylindrical inner envelope closed by insulating plates at its ends and the second element consists of a conductive wire stretched between the two extreme insulating plates .

 Advantageously, the insulating elements consist of insulating joints of dimensions corresponding to those of the surfaces of the sections of each of the parts.

According to a characteristic of the invention, the means for measuring electric current comprise:
collection and transposition means which receive the currents from each identical part of the sensor while maintaining them at the same potential and which deliver voltages as a function of the collected currents,
- A detectcur which receives the voltages of the collection and transposition means and which delivers at least one signal proportional to the amplitude of said voltages and allowing the determination of the corresponding angle of inclination. This detector delivers as many signals as the sensor has measurement axes.

 These measurement means further include a low-pass filter at the output of the detector to remove the residual components of the signal whose frequencies are harmonic with that of the current excitation of the second conductive element.

According to a characteristic of the invention, the supply means comprise
a current generator delivering an electric excitation current from the second conductive element,
control means comprising an oscillator delivering a periodic signal, a reference voltage generator delivering a reference voltage, calibration means receiving the periodic signal and the reference voltage for delivering a control signal from the generator current range in amplitude.

 Advantageously, the detector receives the periodic signal and delivers a signal proportional to the amplitude of the part of the voltages from the collection and transposition means which are in synchronism with the control signal.

Other particularities and advantages will appear on reading the description given by way of nonlimiting example and with reference to the appended drawings which represent:
FIG. 1, the diagram of a device for measuring tilt angles according to the state of the art,
FIG. 2, the diagram of a device for measuring tilt angles according to the present invention according to a first embodiment,
FIG. 3, the assembly diagram of a practical embodiment of a sensor according to FIG. 2,
FIG. 4, the diagram of a sensor according to the invention according to an alternative embodiment,
FIG. 5, the diagram of a second embodiment of the sensor 10 according to the invention,
FIG. 6, the diagram of a particular embodiment of the electronic measurement means according to the invention,
FIG. 7, the diagram of a particular embodiment in accordance with the invention of the detection and supply means,
- Figure 8, the diagram of a particular embodiment of the control means.

 FIG. 2 shows a device for measuring tilt angles according to the invention.

 The device comprises a sensor 10 and electronic measurement means 50. The sensor 10 shown in this figure corresponds to a first embodiment according to the invention.

 The sensor 10 according to this embodiment comprises a first hollow conductive element it having an inner envelope of spherical shape and a second conductive element 12 of spherical shape such as a ball. The conductive element 12 is centered in the conductive element 11.

 This sensor 10 admits as many desired symmetry planes and consequently makes it possible to produce, as necessary, a monoaxial or multi-axial inclinometer.

 In this figure, there is shown by way of example a sensor 10 of the monoaxial type.

 To this end, the first conductive element 11 is divided into two identical parts 13, 14, each forming a spherical half cap in this embodiment. The two parts 13 and 14 are separated by an electrical insulation element 15 which makes it possible both to achieve electrical insulation between the two conductors 13, 14 and also to maintain the center of the second conductive element 12 and its electrical supply.

 In the case where the inclinometer is of the multiaxial type, the conductive element 11 is divided into as many ontic parts as necessary. Each part is electrically insulated by insulating elements such as element 15. Only one of these elements 15 is however sufficient to keep the central element 12 and its power supply in place.

 Connection means such as an electrical terminal 16, 17, are fixed on each part of the conductive element 11 and make it possible to measure a current, these terminals being connected to the measuring means.

 A conductive liquid 18 fills part (generally half) of the interior volume of the conductive element 11 so that the element 12 is in permanent contact with the liquid.

 The central sphere 12 is supplied with current by a current generator 53 as shown, for example in FIG. 6. The supply is made, for example, by means of an insulated conducting wire 19 connected to the generator and to the sphere 12.

 The two spherical caps 13 and 14 are maintained at a constant value potential as described with reference to FIG. 6.

 The current injected by the sphere 12 into the liquid 18 is distributed over the caps in proportion to the surface of the caps bathed by the resistive liquid 18.

 The axis of the sensor X, X 'is defined as the line joining the two opposite vertices of the two caps. The separation plane isolating these two caps is then perpendicular to it.

 In the case where this axis is horizontak, ie parallel to the surface of the liquid, each cap is bathed symmetrically on the same surface. These two caps 13, 14 then collect the same intensity of current: half of that injected by the central ball 12. The angle between the axis of the sensor and the vertical is equal to Pi / r, thus the inclination ( given with respect to the horizontal plane) is zero.

 In the intermediate cases, due to the spherical geometry and the semi-filling of the cellar, the difference in intensity of the currents collected by the two caps is proportional to the angle between the axis of the sensor X, X 'and the horizontal plane, that is to say the inclination, this independently of any rotations around the axis of the sensor.

 The inclinometer is insensitive to the value of the resistivity of the liquid, as a first approximation and within reasonable limits, because the measurement is based on the principle of a distribution of the current.

 In Figure 3 there is shown a circuit diagram of a practical embodiment of the sensor. According to this practical example the hollow element 11 of spherical shape is obtained by machining two half-spheres (for example with a diameter equal to 1000 mm) with great precision in a block of solid copper or any other conductive material . The surface condition of the two interior surfaces has been worked so as to eliminate any defect which could introduce an error on the surfaces bathed by the liquid, therefore a deviation of the measurements thereafter.

 The blocks 23 and 24 containing the half-spheres 13, 14, were drilled and tapped so as to be able to be assembled one against the other by means of screws made of a non-conductive material such as nylon, because the use of screws made of non-conductive material prevents any direct and undesirable electrical contact between the two hemispheres.

 A small threaded orifice 26 of small diameter, for example 3 mm, is practiced at the geometric center of each of the half-spheres thus produced. This orifice allows by L9 jite the introduction of the resistive liquid inside the spherical cellar; the other orifice makes it possible to rebalance the surface condition of the hemispheres.

 Advantageously, the insulating element 15 is produced from a plate 25 which makes it possible both to isolate the blocks 24 and 23 and to maintain the ball 12 at the center of the sphere formed by the two half-spheres 13 , 14, machined in these blocks. This pressing plate therefore has an insulating surface at least equal to the facing surfaces of the two half-blocks 23 and 24 and of the smallest possible thickness. This insulation plate was produced by way of example from a resin-fiberglass plate of small thickness (1 mm) such as the plates used to make the printed circuits.

 This embodiment has the advantage, using the characteristics of this plate, of being able to bring in spite of a conductive line 19 of small thickness to the center of the sphere. This line 19 is subsequently isolated by means of a light film of polyester resin passed with a brush.

 The plate 25 is precut to the exact dimensions of the two blocks of copper (or any other conductive material) and is partially hollowed out on a surface corresponding to the projection of the sphere 11 over its largest diameter. Only a small strip 29 (about 3 mm wide) passing through the center of the surface is not cut.

 By chemical treatment, according to the method conventionally used to make printed circuits, a spite of copper or any other conductive material (of width approximately 1.5 mm) is produced. on the plate from one of its outer edges to its center, the line 19 being precisely on the strip 29.

 Is practiced on the plate, before proceeding to its recess, a hole of diameter equal to that of the ball 12 which must be implanted. The contact between the edge of the hole and the copper tape previously removed is tinned. The ball can then come to take its place in the hole. It is soldered to the copper tape by tin solder.

 After having produced the insulating part 25 provided with its ball 12, the various elements of the sensor can be assembled. The sensor is sealed for example by coating the two faces of the part 25 in contact with the two hemispheres with silicone sealant.

 The resistive solution is introduced into the assembled sphere, for example by means of a syringe through one of the orifices 26 provided for this purpose. The volume necessary for filling the sensor corresponds in this embodiment very exactly to the interior half volume of the sensor after assembly.

 By way of example, the resistive solution is obtained by diluting copper chloride II in deionized water. The concentration of the solution is a direct function of the choice of resistivity desired.

In fact, in the very principle of the operation of the sensor, the resistivity of the solution does not matter. It is simply chosen from the optimum operating range of the signal detection electronics (in order to obtain an overall resistance between the central ball and the two hemispheres together of the order of 500 # to 1 k #, for example) .

 Advantageously, to avoid the electrolysis phenomena that can occur between the hemispheres and the solution, we choose a salt from the same metal as that used in the manufacture of the two blocks (so if the 3n uses copper we will take a salt based on copper: CuCl).

2
FIG. 4 shows the diagram of a sensor 10 according to the invention according to an alternative embodiment. This variant in fact corresponds to the production of a multiaxial sensor according to the embodiment described with reference to FIG. 3.

In the embodiment shown in Figure 2 and in the practical example of Figure 3, the sensors are of the monoaxial type. The measurement angle is the angle between the axis of the sensor and the horizontal plane.

 Sufficient for certain applications, such a device does not make it possible to completely determine the direction that the vertical takes in a reference linked to the solid on which the sensor is fixed.

 An inclinometer with two orthogonal axes allows an ambiguity to solve the problem, in fact the two angles thus measured correspond to two canes (orient) respectively along the two axes of the sensor. Except in special cases, two solutions are possible for the direction of the vertical: they correspond to the two generatrices formed by the intersection of the two cones. When an additional item of data makes it possible to remove this ambiguity, such a two-axis device is sufficient, otherwise a third inclinometer device with three orthogonal axes, called "triaxial inclinometer", must be considered.

 The basic principle of the sensor according to the invention easily extends to multiaxial configurations. For this we proceed to a cut into as many blocks as desired, and a separation of the blocks two by two by an electrically insulating barrier (leaving the central cavity free), the conductive sphere. 11 along the perpendicular plane of each axis containing the center of the sphere 12.

 Thus for a configuration with two orthogonal axes, the sphere is subdivided into four equal portions along two meridians. Similarly for three orthogonal axes, we obtain eight spherical portions corresponding to a cut along two meridians - and the equator as shown in Figure 4.

 The current collected by each portion from the central ball is proportional to the surface bathed by the liquid which generally fills half of the cavity, this when the electrical potentials of the spherical portions are independently maintained at the same value.

Figure 4 therefore corresponds to the embodiment of a sensor comprising 8 parts 251 electrically isolated such as parts 231, 232 on each of which is fixed a terminal 161, 162
sensor therefore has three axes of measurement.

 FIG. 5 corresponds to a second embodiment of a sensor according to the invention.

According to this embodiment, the sensor 10 comprises a first conductive element 31 constituted by a hollow cylinder and the second conductive element 32 is constituted by a wire of small diameter stretched along the longitudinal axis of the cylinder. The cylinder 31 is closed at its two ends by circular insulating plates 36, 37 enabling both to close the cylinder hermetically and to keep the conductive wire 32 tight.

 The cylindrical cellar thus formed is half-filled with a resistive liquid 18.

 According to the invention, the first conductive element, ie ± the cylinder 31, is made up of two identical parts constituting cylindrical half-envelopes 33, 34 (this embodiment only allows monoaxial operation) .

These cylindrical envelopes are both mechanically joined and electrically separated by an electrical insulation element 35. The holding function along the central axis of the element 32 is provided for example by the two end plates 36 and 37.

The supply of this conductive wire 32 is made by the supply means via connection means (not shown). A terminal 38, respectively 39 is fixed on the half-envelope 33, respectively 34. These terminals make it possible to electrically connect the half-envelopes to the measurement means.

 FIG. 6 represents the diagram of resolution of the electronic measurement means 50 according to the invention for a monoaxial sensor, the sensor 10 having been shown in this figure very schematically.

 The means 50 comprise means for measuring currents 51 and supply means 52. The means 52 comprise a current generator 53 and control means 54 making it possible to control the current excitation of the sensor 10 and possibly to synchronize the detection of the currents measured il and i2 taken from the terminals which are fixed to the sensor.

 The control means 54 include calibration means such as a calibration gatekeeper 540, an oscillator 541 and a reference voltage generator 542 acting on the calibration gatekeeper 540 so that the latter, which is powered by the oscillator 541 delivers a periodic signal such as a square signal calibrated in amplitude Hc and proportional to the reference voltage Vref.

The generator then delivers a current i
o
The detection means 51 comprise a transposing collector 510 which receives the currents il and i2 such that i = (1/2 + #) io and i = (1/2 -) io, α being the angle 1 # o 2 # o of inclination of the axis of the sensor XX 'relative to the horizontal plane. This circuit 510 converts these currents into two voltages El and E2 of reverse polarity such that E1 = RT.io α / #, E2 = RT # io (- #) / #, RT being a
o To T internal resistance of the circuit enabling the
current-voltage conversion.

The means 51 also include a detector 511 followed by a low-pass filter 512. The detector receives the two voltages of reverse polarity
E1, E2 and is preferably synchronized by the 5V signal from the oscillator 541. The low-pass filter 512 operates after the synchronous detection. The detector 511 delivers at output a signal proportional to the amplitude of the difference of the voltages E and E. When the detector
1 2 is synchronous the amplitude disturbances are also greatly attenuated. The low-pass filter then makes it possible to eliminate the residual components of the output signal of the detector, of frequencies close to and greater than the frequency of the excitation. The output signal of the low pass filter is proportional to the angle. The output of this filter 512 is connected to adaptation means 513 in gain and in impedance making it possible to connect by a connection S the device of the invention to reading means.

 The generator 53 makes it possible to inject a calibrated current into the electrolyte 18 of the sensor at the level of the ball 12 or of the wire 32. The measurement circuit 51 makes it possible to collect for each of the two parts 13, 14 (or 33, 34) the corresponding currents i and i in 1 2 maintaining them at the same electrical potential without any real interconnection between the two parts. The processing of the difference of the two currents allows, as described above, the measurement of the angle of inclination of the sensor.

By way of remark, the connection of the calibration gatekeeper to the collector-transposer shown in FIG. 6 makes it possible to subtract a regal current from a part of the excitation current so as to increase the dynamics of the voltages E, E in the voltage ga entry. The following values were taken as an example:
R9 = R15 = 3.01 KQ
R10 = R11 = 2.05 K #
R14 = 464
R20 = 20.5 KIL, R21 = R22 = 51.1 KR
C5 = C9 = 4.7 pF
C6 = 1 rF, C11 = 22 pF
The high resolution of the device is given by synchronous detection and differential analysis. The detector 511 used comprises four analog switches I mounted in a ring (for example of the type 4016).

By way of example, the following values have been taken for the various elements constituting this detector
R12 = R13 = 511 #
R7 = R8 = 20.5 k #
R16 = R17 = R19 = R18 = 51.1 k #
C10 = 10 nF
C7 = C8 = 220 pF
The low-pass filter 512 eliminates after synchronous detection the residues at the frequency of the oscillator and determines the bandwidth of the signal available at the outputs of the device. a second order filter type assembly from a differential amplifier was used. For example, the following values have been taken for the various elements constituting this filter:
R23 = 100 KQ
R26 = R25 = R24 = 46.4 #
C13 = C14 = 220 nF
C12 = 1nF
In FIG. 8, an exemplary embodiment of the control means 54 is shown in very detail.

 Oscillating 541 makes it possible to have a square signal of a stable frequency, low frequency (practically 100 Hz to 10 KHz) with a duty cycle of 50% in order to respect the temporal symmetry of the signal.

As an example, the following values have been taken for the elements constituting the oscillator:
R37 = R38 = 100 K St
R39 = 14.7 k #, R41 = 10 M #, R42 = 46.4 k #
R40 = 205 # C20 = 22 nF
The reference voltage generator 542 conditions the calibration of the square excitation signal and can, if necessary, also be used to create fixed offset voltages in the case where a single-voltage supply voltage of the device is used. As an example, we took the following values for the elements making up this generator:
R43 = R45 = 51.1 KQ
R44 = 24.9k #, R46 = 12.1k #
P3 = 47 K C22 = 220 nF
C21 = 10 Z1: 2.5 V reference voltage element, commercial reference for example LM336.

 The calibration gatekeeper 540 is based on the same principle (four switches mounted in a ring) as the synchronous detector and performs a synchronous inversion function on the excitation signal, of the reference voltage according to a desired gain.

By way of example, the following values have been taken for the elements constituting this gatekeeper:
R49 = R52 = 10k #
R50 = R51 = 51.1 k #
C23 = 1 nF
R47 = R48 = 20.5 KQ
The differential amplifiers used in the various functions are conventional integrated functions of operational amplifiers such as the amplifiers marked LF347.

 The processing electronics are little different (in principle) in the multiaxial case from that described previously in the case of the monoaxial sensor. The parts described concerning the excitation signal injected at the level of the central ball, are without modification.

 The corresponding currents of each of the portions (on 8 connecting wires for the triaxial configuration) are transposed into voltages while maintaining the potentials of the portions at the same value, using for example as previously mounted differential amplifiers (as many as portions) in input voltage control. It will then be possible by simple summation of the tensions (by six groups of four for the triaxial configuration) to reconstruct the case of two opposite hemispheres (three pairs of signals).

 Identical channels, comprising, as in the example of the monoaxial sensor, possibly synchronous detection and a filtering stage, process in parallel each pair of signals available after summation corresponding to each axis (ie 3 measurement channels for the triaxial).

 It is also possible to carry out a mixing between the intensities of the currents collected from any spherical portions of the same "sensitive sphere" in other words from the same sensor or by extension to several "sensitive spheres", that is to say that is to say to several sensors.

 We will cite for example the simple case of two moncaA ales configurations processed by the same electronics, similar to that corresponding to a two-axis configuration, but performing a subtraction of the image voltages at the level of the "transposing collector") (we will refer for example in the diagram of figure 6).

 The device thus formed allows, easily and for the benefit of an optimal resolution, to perform differential inclinometry.

 The device which is the subject of the invention therefore has the following advantages.

- the sensitive part of the sensor does not involve any moving mechanical part. Its design is simple (essentially a few solid constituents and a liquid). This guarantees the qualities of robustness, ease of manufacture (stamping of the two dem; -spheres) and good long-term resistance;
- the sensor for a sensitive axis allows a practically total measurement dynamic, it is around 180 (the non-linear zones at the limits of the dynamic, linked to the presence of the insulation elements, can be less than the degree). The measurement is reliable whatever the rotation around the sensitive axis. This device makes it possible to obtain measurements on the 1,800 with 3,600 of freedom;
- the current consumption of the entire device (sensor part + electronics) remains low (25 mA for the monoaxial prototype produced). The consumption can in fact be less than 5 mA for a monoaxial sensor and of the order of 10 mA for a triaxial sensor by the use of active components with low consumption.

Claims (11)

REVENDICATIOAS  1. Device for measuring tilt angles comprising a sensor (10) and electronic measuring means (50) characterized in that the electronic measuring means (50) comprise  - means for measuring electric currents (51) and supply (52) and in that the sensor comprises  a first hollow conductive element (11, 31) comprising at least one plane of symmetry, this element being divided at the level of this plane of symmetry into two identical parts, electrically isolated from each other, each part being connected to the current measurement means ( 50),  a second conductive element (12, 32) centered inside the first element (11, 31) and equidistant from the different parts, this element being connected to the supply means (52), and  a conductive liquid (18) filling part of the interior volume of the first element so as to be in permanent contact with the second element.  2. Measuring device according to claim 1, characterized in that it comprises electrical insulation elements (15, 35) which make it possible to isolate the different parts constituting the first element.  3. Measuring device according to any one of claims 1 or 2, characterized in that on each insulated part are fixed connection means (16, 17) for connecting each insulated part to the measuring means.  4. Device according to any one of claims there 3, characterized in that the first element t11) hollow conductor has an inner envelope of spherical shape and that the second element (12) is of spherical shape.  5. Device according to claim 4, characterized in that the insulation elements (15)  consist of insulating plates (25) cut out of a hinge to have a hollowed out shape corresponding substantially to that of the first element (11), at least one of these plates comprising a tab (29) the end of which holds the second element ( 12) and on which is located an insulated conductor (19) connecting this element to the supply means (52).  6. Device according to any one of claims 1 to 3, characterized in that the first hollow conductive element (31) has a cylindrical inner envelope closed by insulating plates (37, 36) at its ends and in that the second element (32) consists of a conductive wire stretched between the two extreme insulating plates (37, 36).  7. Device according to claim 6, characterized in that the insulation elements (35) consist of insulating joints of dimensions corresponding to those of the surfaces of the sections of each of the parts.  8. Device according to any one of claims 1 to 7, characterized in that the means for measuring electric current (51) comprise  - means of collection and transposition (510) which receive the currents (i, i)  1 2 of each identical part of the sensor while maintaining them at the same potential and which deliver voltages (El, E2) which are functions of the collected currents,  - a detector (511) which receives the voltages (El, E2) of the collection and transposition means (510) and which delivers at least one signal proportional to the amplitude of said voltages and allowing the determination of the angle '' inclination corresponding.  9. Device according to claim 8, characterized in that the means for measuring electric current (51) further comprises a low-pass filter (512) at the output of the detector (511) to remove the residual components of the signal whose frequencies are harmonic with that of the current excitation of the second conducting element.  10. Device according to any one of claims 1 to 9, characterized in that the supply means (52) comprise  - a current generator (53) delivering an electric excitation current from the second conductive element (12, 32),  - control means (54) comprising an oscillator (541) delivering a periodic signal (SY), a reference voltage generator (542) delivering a reference voltage (short), det calibration means (540) receiving the signal periodic (SY) and the reference voltage to deliver a control signal from the current generator (53) calibrated in amplitude (Hc).  11. Device according to any one of claims 1 to 10, characterized in that the detector receives the periodic signal (SY) and delivers a signal proportional to the amplitude of the part of the voltages from the collection and transposition means which are in synchronism with the control signal.