LEVEL SENSOR

Description

Technical field of the invention

[0001] The present invention relates to a level sensor. It applies, in particular, to microwave radar technology.

[0002] A microwave radar is a device that measures the distance between the device and an obstacle. To do this, a transmitter sends electromagnetic waves at an obstacle. These waves are reflected off the obstacle and returned to a receiver.

[0003] The frequency band is between 300Mhz and 300Ghz, i.e. wavelengths in air or in a vacuum between 1m and 1mm. Prior art

[0004] Documents US2019 / 316951 and CN108225482 represent an example of prior art with a level sensor for measuring a distance between a transceiver device and a target. However, these documents require a large amount of energy to operate and do not significantly improve the reliability of the measurements.

[0005] An exemplary embodiment of the prior art of a transmitter-receiver device that allows a distance between the device and an obstacle to be measured is shown in the figure 1 .

[0006] There figure 1 represents a schematic diagram with on one side a transmitter-receiver device, noted 30, and on the other side a target, noted 31.

[0007] The transceiver device 30 is in transmission mode and sends electromagnetic waves with frequency modulation at a speed close to that of light at an angle α. Arrow A indicates the direction and sense of the emitted waves. When the waves come into contact with the target 31 to be measured, they will be reflected more or less on this target 31 to be measured depending on the permittivity of this material. Arrow B indicates the direction and sense of the reflected waves.

[0008] Depending on the permittivity of the material, the waves will return to the transmitter-receiver device 30 in reception mode with an amplitude to calculate the distance between the transmitter-receiver device 30 and the target 31 to be measured.

[0009] In this configuration, the transceiver device 30 requires a large amount of energy to operate because some transmitted waves are not reflected back to the transceiver device 30. Presentation of the invention

[0010] The present invention aims to overcome these drawbacks with a completely innovative approach.

[0011] To this end, the present invention aims at a level sensor for measuring a distance between a transmitter-receiver device and a target, the transmitter-receiver device has a mode of emission of electromagnetic waves at an angle α and a mode of reception of electromagnetic waves, called echo, remarkable in that it comprises: a lens positioned between the transceiver device and the target at a distance, said lens deflecting the electromagnetic waves of the transceiver device at the angle α to change the angle of the electromagnetic waves at an angle β; a distance variation element between the lens and the transceiver device; an electronic radar card provided for controlling the transceiver device for sending electromagnetic waves and processing the received echo and calculating a distance with the target, said calculation of a distance between the transceiver and the target is carried out from the propagation speed of the wave in its medium, the frequency of the electromagnetic waves and the response time between the transmission mode and the reception mode;the radar electronic card is configured with a reference echo and adapts the amplitude of the emitted electromagnetic waves, with the realization of successive shots and comparison between the echoes of the successive shots and that of reference; a communication card between the level sensor and a terminal to transmit the information of the calculation of the distance coming from the electronic card; a battery to power the different elements of the level sensor.

[0012] Thanks to its integrated power supply, the level sensor can be placed in places without an electricity network.

[0013] In addition, its compact size also allows it to be placed in tight spaces.

[0014] According to one variant, the radar electronic card and the communication card are on a single electronic card which fulfills both functions.

[0015] According to an exemplary embodiment, the system uses pulsed radar or coherent pulsed radar.

[0016] In another embodiment, the system uses the principle of FMCW (Frequency-Modulated Continuous-Wave) to determine the distance between the transmitter and receiver device and the target. The electronic board for processing electromagnetic waves is a microprocessor that controls the transmitter and receiver. A digital-to-analog converter transforms the control code into an analog voltage signal. A special VCO (Voltage Controlled Oscillar) radio frequency generator generates a signal at a frequency proportional to the analog voltage signal. A bandwidth filter is used to eliminate spikes and harmonics to leave only the programmed frequency.The signal is then sent to a coupler, which will send part of the signal to a mixer and the other part of the signal to a power amplifier. The power amplifier will then increase the intensity of the transmitted wave to the desired power. Once the wave is amplified, the wave is emitted and sent to the target via the transmitting antenna. Once the wave has reflected off the target, it is picked up by the receiving antenna. The receiving antenna then converts the returning electromagnetic signal into a radio frequency voltage. The return signals are extremely weak. They are then amplified by a low-noise amplifier. The amplified signals are then transmitted to the mixer. The mixer multiplies the emitted and received signals, producing at its output a signal whose frequency is the difference between that of the emitted signal and that of the received signal at a given time t.A low-pass filter is then applied to the signal to filter out unwanted high frequencies. The signal is then amplified using an amplifier and passed to an analog-to-digital converter. The output signal processing gives the frequency between the received and transmitted signal.

[0017] Transmission and reception are simultaneous. The transmitted signal is linearly frequency modulated (frequency ramp). Measuring the frequency difference between transmission and reception allows the calculation of the propagation time (round trip) of the transmitted signal and consequently the distance (round trip) between transmitter and target.

[0018] By applying an inverse function to the frequency of the signal at the mixer output, we obtain the time taken for a wave to propagate to the target and back. Knowing the propagation speed of the wave, we can then calculate the distance between the transmitter and receiver and the target. T = 1 f 2 D = v ∗ T D = v 2 ∗ f with: - T the time taken for a wave to travel back and forth between the transmitter-receiver and the target (in s) f the frequency of the signal at the mixer output (in Hz) D the distance between the transmitter-receiver and the target (in m) v the speed of the wave (in mm / s).

[0019] Knowing the height of a location allows for a measurement of available stock by calculating the volume of material still available from the height. In this case, the level sensor is positioned at the top of a container. Another application of the system is water level measurement for flood monitoring, flooding, or storm overflows. The level sensor is then placed at the top of a pipeline.

[0020] Installing a lens in the level sensor will allow for more accurate measurement and will allow measuring greater distances compared to a transceiver device without a lens since the signal is focused.

[0021] The distance information allows the level sensor to be used in different applications and adapts according to the task assigned to it. The level sensor also adapts to different parameters such as distance, the size of the surface to be measured or the condition of the surface. Thus, for silo measurement, a wide opening angle is preferred to cover a larger surface. In silos, the surface to be measured is most often chaotic. To obtain a measurement that is as close as possible to reality, a wide opening angle is applied. This allows a larger surface to be covered and the volume of material present in the silo to be better estimated.

[0022] For water height measurement, the system will be able to adapt depending on the flow, which will give us a more or less chaotic surface. Thus, if we find obstacles to the flow in fast-flowing water, the surface will no longer be flat but chaotic, and a wide opening angle will be appropriate. The wide opening angle will allow us to better estimate the average water height. Whereas when the flow is slow and without obstacles, the surface will be smooth. A low opening angle is then more appropriate because it allows for a more precise measurement.

[0023] The invention is advantageously implemented according to the embodiments and variants set out below, which are to be considered individually or in any technically effective combination.

[0024] In one embodiment, the variation element is a motor connected to the transceiver device and moving said transceiver device along an axis, the lens being fixed.

[0025] In one embodiment, the variation element is a motor connected to the lens and moving said lens along an axis, the transmitter-receiver device being fixed.

[0026] In one embodiment, the variation element is a motor connected to the lens and the transceiver device and moving said lens relative to the transceiver device.

[0027] In one embodiment, the lens is composed of two surfaces, a first surface facing the transceiver device and a second surface facing the target, the first surface of the lens or the second surface of the lens having a shape selected from the following shapes: concave, convex, spherical, planar and Fresnel.

[0028] In one embodiment, a waterproof housing makes the level sensor waterproof and moisture resistant.

[0029] In one embodiment, the lens is composed of one or more materials having a relative permittivity of between 1.5 and 15.

[0030] In one embodiment, the angle β is between 1 and 60°.

[0031] In one embodiment, the radar electronic card is configured with a reference echo and adapts the amplitude of the emitted electromagnetic waves, called signal, according to the following conditions: sending a first sending signal from the transceiver device in transmission mode; receiving the first return signal by the transceiver device in reception mode; and comparing the first return signal with the value of the reference echo only if the first return signal is beyond a value of plus 10% or minus 10% of the value of the reference echo then sending a second amplitude of the sending signal from the transceiver device according to the following conditions so that the value of the second amplitude of the sending signal is equal to: the value of the amplitude of the first sending signal plus a value between 1% and 10% of the amplitude of the first sending signal, if the first return signal is less than 10% of the reference echo; the value of the amplitude of the first sending signal minus a value between 1% and 10% of the amplitude of the first sending signal, if the first return signal is greater than 10% of the reference echo.

[0032] The reference echo is pre-recorded. In another example, the reference echo is extracted from an abacus.

[0033] If the first return signal is within the reference range plus 10% and minus 10% of the reference echo, then the amplitude of the emitted electromagnetic waves is correct.

[0034] The device has an adaptive power function that allows the transmission power to be set as best as possible in order to obtain an echo whose amplitude is adapted to optimal analysis (echo strong enough for analysis) or to reduce the transmission power if the target is close, thus gaining energy autonomy. The device performs an initial measurement at a predefined power, depending on the amplitude of the echo received, the device adapts its transmission power, increasing or decreasing.

[0035] The validity of the echo amplitude is defined by a threshold that decreases linearly with the distance to the target. Indeed, at equal transmission power, for the same target, the amplitude of the echo decreases with the distance, this phenomenon is due to the attenuation of the signals with the distance.

[0036] Concerning successive shots and to save energy (consumed at each emission) and optimize the quality of the result, the system can be explained as follows: we make a first shot (a sending and a receiving) if the two are too different, then we start again as many times as necessary.

[0037] The interest of these successive shots is the variation of the power or the voltage for the radar shot, adapting the power during the first shots allows to save energy and to be more precise on the results.

[0038] According to a second aspect, the present invention relates to a method of a level sensor for measuring a distance between a transmitter-receiver device and a target, remarkable in that it comprises the following steps: emission of electromagnetic waves by a transceiver device having an electromagnetic wave emission mode at an angle α and an electromagnetic wave reception mode, called echo, positioning a lens between the transceiver device and the target at a distance, said lens deflecting the electromagnetic waves of the transceiver device at the angle α to change the angle of the electromagnetic waves at an angle β; variation by a variation element modifying the distance between the lens and the transceiver device;control by an electronic radar card intended to control the transmitter-receiver device for sending electromagnetic waves and processing the received echo and calculating a distance with the target, said calculation of a distance between the transmitter-receiver and the target is carried out from the propagation speed of the wave in its medium, the frequency of the electromagnetic waves and the response time between the transmission mode and the reception mode; communication by a communication card between the level sensor and a terminal to transmit the information of the calculation of the distance coming from the electronic card; signal processing by an electronic radar card configured with a maximum amplitude of the electromagnetic waves, a reference echo and the storage of a saved amplitude value equal to 50% of the maximum amplitude of the electromagnetic waves;said radar electronic card adapts the amplitude of the emitted electromagnetic waves, called signal, according to the following sub-steps: sending a first sending signal from the transmitter-receiver device in transmission mode, the value of the amplitude of the first sending signal is equal to the value of the saved amplitude; reception of the first return signal by the transmitter-receiver device in reception mode;comparing the first return signal with the value of the reference echo, and only if the first return signal is outside a reference range of plus 10% and minus 10% of the value of the reference echo then sending a second amplitude of the sending signal from the transceiver device, according to the following conditions so that the value of the second amplitude of the sending signal is equal to: the value of the amplitude of the first sending signal plus a value between 1% and 10% of the amplitude of the first sending signal, if the first return signal is less than 10% of the reference echo; the value of the amplitude of the first sending signal minus a value between 1% and 10% of the amplitude of the first sending signal, if the first return signal is greater than 10% of the reference echo; storing the value of the second amplitude of the sending signal at the saved amplitude value;repetition of the sub-steps as long as the value of the first return signal is not between plus or minus 10% of the value of the reference echo.;

[0039] The advantages, aims and particular characteristics of this method being similar to those of the level sensor which is the subject of the present invention, they are not recalled here. Brief description of the figures

[0040] Other advantages, aims and characteristics of the present invention emerge from the following description given, for explanatory and non-limiting purposes, with reference to the appended drawings, in which: [ Fig. 1 ] there figure 1 (relating to the prior art) represents a block diagram of a transmitter-receiver device; [ Fig. 2 ] there figure 2 represents a schematic diagram of a transmitter-receiver device and a chaotic surface target; [ Fig. 3 ] there figure 3represents a schematic diagram of a transmitter-receiver device and a flat surface target; [ Fig. 4 ] there figure 4 represents a schematic diagram of the different elements that make up the level sensor; [ Fig. 5 ] there Figure 5 represents a diagram to explain the signal amplitude with a small target. [ Fig. 6 ] there figure 6 represents a diagram to explain the signal amplitude with a large target. [ Fig. 7 ] there figure 7 represents a diagram to explain the measurement with parasitic targets. [ Fig. 8 ] there figure 8 represents a diagram to explain how the level sensor avoids parasitic targets. [ Fig. 9 ] there figure 9 represents operating diagrams of the level sensor to illustrate the data of the figure 10 . [ Fig. 10 ] there figure 10 represents measurement data of the diagrams of the figure 9 . [ Fig. 11 ] there figure 11represents different lens shape. Description of the embodiments

[0041] There figure 1 represents has been described previously.

[0042] There figure 2 shows a schematic diagram of a transceiver device and a target with a small distance.

[0043] Between the transmitter-receiver device 30 and a target 31, a lens 32 is placed in front of the sent wave. The lens 32 is made of a material that allows the wave to pass through it.

[0044] The particular shape of the lens 32 makes it possible to focus the waves sent with an angle α at an angle β. By varying the distance between the transmitter-receiver device 30 and the lens 32, the angle β can be modified. The closer the transmitter-receiver device 30 and the lens 32 are, that is to say the smaller the distance, noted d' in the figure, will be, the larger the angle β' will be and will be able to cover a larger detection zone.

[0045] Conversely, on the figure 3 , the greater the distance d" will be, the smaller the angle β" will be.

[0046] There figure 3 takes up the elements of the figure 2 .

[0047] Varying the angle β allows the waves to be focused on a very specific area in order to give a more precise measurement.

[0048] For a lens 32 of negative camber plano-convex shape and by varying the distance d between the transmitter-receiver device 30 and the lens 32, an opening angle of between 8° and 20° is obtained.

[0049] The opening angle can vary more with another lens shape 32.

[0050] There figure 4 shows a schematic diagram of the different elements that make up the level sensor.

[0051] The level sensor is used to measure a distance between a transceiver device 30 and a target 31. The transceiver device 30 has an electromagnetic wave transmission mode and an electromagnetic wave reception mode.

[0052] This figure shows a lens 32 positioned between the transmitter-receiver device 30 and the target 31.

[0053] A variation element makes it possible to vary the distance between the lens 32 and the transmitter-receiver device 30. Example of the variation element:

[0054] In one example, a gear wheel is attached to the output shaft of a motor. The gear wheel drives a rack attached to the transceiver device. The lens is fixed. Rotating the motor then varies the distance d between the transceiver and the lens.

[0055] In another example, a threaded part is attached to the output shaft of a motor. This part can only have a rotational movement. A threaded part is attached to the transceiver device. The rotation of the threaded part is blocked relative to the frame. The lens is fixed. The rotation of the motor and the threaded part in the threaded part causes the transceiver device to translate. The rotation of the motor then allows the distance d between the transceiver and the lens to be varied.

[0056] In another example, a threaded part is attached to the output shaft of a motor. This part can only have a rotational movement. A tapped part is attached to the lens. The rotation of the tapped part is blocked relative to the frame. The transceiver device is fixed. The rotation of the motor and the threaded part in the tapped part causes the translation of the lens. The rotation of the motor then makes it possible to vary the distance d between the transceiver and the lens.

[0057] These examples are here for informational purposes only. The purpose of the variation element is to change the distance between the transmitter-receiver and the lens.

[0058] An electronic radar card 33 is provided to control the transmitter-receiver device 30 for sending electromagnetic waves and processing the received signal as well as calculating a distance with the target 31.

[0059] A communication card 34 between the level sensor and a terminal allows the transmission of distance calculation information from the electronic card.

[0060] A 35 battery provides power to the various elements of the level sensor.

[0061] The transmitter-receiver device 30 and the lens 32 are positioned along the same axis.

[0062] For example, the axis is an axis noted y, said axis is collinear with the median axis of the electromagnetic waves.

[0063] To vary the distance d either: - the transmitter-receiver device 30 is moved along the y axis using a motor 36 while leaving the lens 32 fixed; - the lens 32 is moved along the y axis using a motor 36 while leaving the transmitter-receiver device 30 fixed; the transmitter-receiver device 30 and the lens 32 are moved simultaneously.

[0064] The transmitter-receiver device 30 is connected to the radar electronic card 33, the latter controls the sending of the signal and processes the received signal to calculate a material level. Once the data has been processed, it is sent via the communicating electronic card to a terminal. The user of the terminal can then read the information.

[0065] A terminal is understood to be: a digital tablet, a mobile phone, particularly of the “smartphone” type, a connected watch, a remote control, a computer or a supervisor.

[0066] The radar electronic board 33 and the communication board 34 as well as the motor 36 are powered by a battery 35. This allows for a transportable wireless system. All of these elements are placed in a box.

[0067] The 37 housing ensures water and dust tightness and protects the system from shocks.

[0068] THE Figures 5 and 6represent diagrams to explain the optimization of the signal amplitude with a larger or smaller target 31.

[0069] The echo is the envelope of the signal reflected by the target. The amplitude of the echo, in dB, depends mainly on the size of the target, as well as the distance between it and the transmitter and receiver. The further away the target is, the more the echo will be attenuated. In order to correctly detect a target, the amplitude of the echo must be sufficient to stand out from the noise. Noise is the signal level measured by the system in the absence of echo. For this, the amplitude must be greater than a predetermined minimum detection threshold.

[0070] If the level sensor sends a signal of amplitude Pe1 to a target 31 of surface S1, the return echo has an amplitude Pr1. The amplitude Pr1 is greater than the detection threshold. Now we send a signal of amplitude Pe2 to a target 31 of surface S2 larger than S1. We keep the same distance L as well as the same angle β. The surface of the target 31 being larger, the wave has more surface to reflect, therefore with a signal of equal amplitude emitted on the 2 surfaces, the echo which is reflected on the larger surface is more powerful. We make sure to send an amplitude Pe2 lower than Pe1 in order to have an echo Pr2 equal to Pr1. By sending the signal of an amplitude Pe2 smaller than Pe1, we reduce the energy consumption of the level sensor and increase its autonomy depending on the nature of the target 31. The radar electronic card 33 allows this processing.

[0071] The level sensor can be adapted to new applications and offers a solution for specific cases where conventional technologies would not allow for accurate measurement. It can therefore be adapted to non-standard container sizes. The opening angle is adapted according to the environment and the "measured target".

[0072] A user can use the same product for multiple applications, it is a versatile product.

[0073] Unlike the ultrasonic level sensor, in the air, electromagnetic waves propagate at a speed that varies very little with environmental conditions (temperature, pressure, air flow, etc.). We can then neglect a speed difference, thus giving us a stable measurement regardless of the composition of the air or its temperature. As long as the temperature does not degrade the material itself. The measurement is then more reliable than that provided by an ultrasonic sensor. an ultrasonic sensor. The level sensor is therefore installable in places where the temperature can vary and is installable in different regions of the globe without having to modify the material.

[0074] The level sensor is mobile and lightweight and is easily carried by hand.

[0075] THE figures 7 And 8 represent diagrams to explain how the level sensor avoids parasitic targets 38.

[0076] There figure 7 shows parasitic targets with a large β angle. The level sensor can autofocus on the target to be measured while avoiding parasitic targets 38.

[0077] There figure 8 shows that when one seeks to measure the distance between the transmitter-receiver device 30 and the target 31, closing the angle β makes it possible to avoid the parasitic targets 38.

[0078] There figure 9 shows a schematic diagram of the level sensor to illustrate the data from the figure 10 . In this example, β' is equal to 20° and β" is equal to 17°.

[0079] The data for β'=20° are on the left and the data for β"=17° are on the right.

[0080] The level sensor sends a signal of amplitude Pe1 to a target 31 of surface S located at a distance L. The signal Pe1 is made up of electromagnetic waves. The distance d' gives us an opening angle β'. For the measurement to be made, the amplitude of the signal must be greater than a predetermined detection threshold.

[0081] In one example, the predetermined detection threshold is set to -80dB.

[0082] Now if we send a signal of the same amplitude Pe1 to the same target 31 with the same surface S located at the same distance L but we replace the distance d' by the distance d" greater than d'. The opening angle β" is then smaller than β'. The signal of amplitude Pe1 is then concentrated on a smaller detection surface. The return echo will then be of an amplitude Pr1' greater than Pr1.

[0083] There figure 10 shows measurement data of the diagrams of the figure 9for an example: detection of a target 31 to 6000mm from the level sensor.

[0084] The dotted line represents the predetermined minimum detection threshold at -80dB.

[0085] Here β'=20° and β"=17°. On the figure 10 , the data relating to β'=20° are on the left and the data relating to β"=17° are on the right. The data in this figure relate to the respective diagrams of the figure 9 The ordinate axis gives the signal amplitude in dB. The abscissa axis gives the distance calculated from the measurement in mm.

[0086] We obtain a return echo for the angle β' with an amplitude of -25dB. We obtain a return echo for the angle β" with an amplitude of -15dB. Knowing that a difference of 3dB between 2 return echoes gives us an amplitude approximately twice as large. Here, by reducing the angle by 3°, we increase the amplitude of the return echo by approximately 2 (25-15) / 3< =10 times.

[0087] Now if we send a signal of amplitude Pe2 following the same configuration as before, that is to say with the same target 31, the same surface S, the same distance d" and the same opening angle β". We make sure to send a signal of amplitude Pe2 lower than Pe1 in order to have an echo of amplitude Pr2 equal to Pr1, knowing that Pr1 is higher than the predetermined detection threshold.

[0088] By sending the signal with an amplitude Pe2 smaller than Pe1, the energy consumption of the present invention is reduced and its autonomy is increased.

[0089] Using the example above, we send an amplitude Pe2=Pe1 / 10. Pr2 will then be equal to Pr1 and we will have reduced the energy needed to send the sending signal by 10. This will have the effect of reducing the consumption of the level sensor and increasing its autonomy.

[0090] Controlling the opening angle β by mechanically varying the distance d then makes it possible to reduce consumption and increase the autonomy of the level sensor depending on the application.

[0091] There figure 11 represents different lens shapes 32.

[0092] The shape of the lens can be 32a plane-plane, 32b converging meniscus negative camber, 32c plano-convex negative camber, 32d equiconvex zero camber, 32e plano-convex positive camber, 32f converging meniscus positive camber, 32g equiconcave zero camber, 32h plano-concave lens negative camber, 32i diverging meniscus negative camber, 32j diverging meniscus negative camber, 32k plano-concave positive camber, 321 fresnel negative camber, 32m fresnel positive camber.

[0093] A Fresnel lens is a plano-convex lens cut from concentric annular sections optimized to lighten the element.

[0094] The lens is composed of one or more materials having a relative permittivity between 1.5 and 15.

[0095] The lens gives an angle β between 1 and 60°. LIST OF REFERENCE SIGNS

[0096] [Table 1] References Designations 30 transceiver device 31 target 32 lens 33 electronic radar card 34 communication card 35 battery 36 engine 37 box 38 parasitic targets [Table 2] References Designations A Direction of emitted waves B Direction of reflected waves d, d', d" distance between the transmitter-receiver device and the lens L distance between the transmitter-receiver device and the target y direction of variation of the distance d

Claims

1. A level sensor for measuring a distance between a transmitter-receiver device (30) and a target (31), the transmitter-receiver device (30) having: - a transmission mode for transmitting a sending signal formed of electromagnetic waves at an angle α and - a reception mode for receiving electromagnetic waves forming a return signal, called echo, characterized in that it includes: - a lens (32) positioned between the transmitter-receiver device (30) and the target (31) at a distance, said lens (32) deflecting the electromagnetic waves transmitted by the transmitter-receiver device (30) at the angle α to change the angle of the electromagnetic waves to an angle β, - an electronic radar board (33) provided to pilot the transmitter-receiver device (30) for sending electromagnetic waves and processing the received echo and to calculate the distance with the target (31) based on the speed of propagation of the wave in its environment, the frequency of the electromagnetic waves and the response time between transmitting the sending signal and receiving the echo, the electronic radar board (33) being configured to adapt the amplitude of the electromagnetic waves transmitted so that the amplitude of the echo received is within a reference range of plus 10% and minus 10% of the amplitude of a reference echo, said reference echo being prerecorded or extracted from an abacus, with successive shots being performed and a comparison between the echoes of successive shots and the reference one.

2. The level sensor according to claim 1, further comprising an element for varying the distance between the lens (32) and the transmitter-receiver device (30).

3. The level sensor according to claim 2, wherein the variation element is a motor (36) connected to the transmitter-receiver device (30) and moving said transmitter-receiver device (30) along an axis, the lens (32) being fixed.

4. The level sensor according to claim 2, wherein the variation element is a motor (36) connected to the lens (32) and moving said lens (32) along an axis, the transmitter-receiver device (30) being fixed.

5. The level sensor according to claim 2, wherein the variation element is a motor (36) connected to the lens (32) and to the transmitter-receiver device (30) and moving said lens (32) relative to the transmitter-receiver device (30).

6. The level sensor according to claim 1, wherein the lens (32) is composed of two surfaces, a first surface facing the transmitter-receiver device (30) and a second surface facing the target (31), the first surface of the lens (32) or the second surface of the lens (32) having a shape selected among the following shapes: concave, convex, spherical, flat or Fresnel.

7. The level sensor according to claim 1, wherein a watertight casing (37) seals the level sensor against water and humidity.

8. The level sensor according to claim 1, wherein the lens (32) is composed of one or more materials having a relative permittivity between 1.5 and 15.

9. The level sensor according to claim 1, wherein the angle β is between 1 and 60°.

10. The level sensor according to claim 1, wherein the electronic radar board (33) is configured to adapt the amplitude of the electromagnetic waves transmitted according to the following conditions: sending a first sending signal (Pe1) of the transmitter-receiver device (30) in transmission mode; receiving the first return signal (Pr1) by the transmitter-receiver device (30) in reception mode; and comparing the amplitude of the first return signal (Pr1) with the amplitude value of the reference echo, and, only if the amplitude of the first return signal (Pr1) is out of the reference range of plus 10% and minus 10% of the reference echo amplitude value, then sending a second sending signal (Pe2) of the transmitter-receiver device (30) according to the following conditions so that the amplitude value of the second sending signal (Pe2) is equal to: - the amplitude value of the first sending signal (Pe1) plus a value between 1% and 10% of the amplitude of the first sending signal (Pe1), if the amplitude of the first return signal (Pr1) is lower than 10% of the reference echo amplitude, - the amplitude value of the first sending signal (Pe1) minus a value between 1% and 10% of the amplitude of the first sending signal (Pe1), if the amplitude of the first return signal (Pr1) is higher than 10% of the reference echo amplitude.

11. The level sensor according to claim 1, further comprising - a communication board (34) between the level sensor and a terminal to transmit the distance calculation information coming from the electronic board, - a battery (35) to power supply the different elements of the level sensor.

12. A level sensor method for measuring a distance between a transmitter-receiver device (30) and a target (31), characterized in that it includes the following steps: - transmitting a sending signal formed of electromagnetic waves at an angle α and receiving, by the transmitter-receiver device (30), electromagnetic waves forming a return signal, called echo; - positioning a lens (32) between the transmitter-receiver device (30) and the target (31) at a distance, said lens (32) deflecting the electromagnetic waves transmitted by the transmitter-receiver device (30) at the angle α to change the angle of the electromagnetic waves to an angle P; - processing the received echo to calculate the distance with the target (31) based on the speed of propagation of the wave in its environment, the frequency of the electromagnetic waves and the response time between transmitting the sending signal and receiving the echo; - storing a saved amplitude value equal to 50 % of the maximum amplitude of the electromagnetic waves; - adapting the amplitude of the transmitted electromagnetic waves according to the following sub-steps: - sending a first sending signal (Pe1) of the transmitter-receiver device (30) in transmission mode, the amplitude value of the first sending signal (Pe1) being equal to the saved amplitude value; - receiving the first return signal (Pr1) by the transmitter-receiver device (30) in reception mode; - comparing the first return signal (Pr1) with the amplitude of a reference echo, and, only if the amplitude of the first return signal (Pr1) is out of a reference range of plus 10% and minus 10% of the reference echo amplitude value, then sending a second sending signal (Pe2) of the transmitter-receiver device (30), according to the following conditions so that the amplitude value of the second sending signal (Pe2) is equal to: - the amplitude value of the first sending signal (Pe1) plus a value between 1% and 10% of the amplitude of the first sending signal (Pe1), if the amplitude of the first return signal (Pr1) is lower than 10% of the reference echo amplitude, - the amplitude value of the first sending signal (Pe1) minus a value between 1% and 10% of the amplitude of the first sending signal (Pe1), if the amplitude of the first return signal (Pr1) is higher than 10% of the reference echo amplitude; - storing the amplitude value of the second sending signal (Pe2) as a saved amplitude value; - repeating the sub-steps as long as the value of the first return signal is not included in the reference range of plus 10% and minus 10% of the value of the reference echo.

13. The level sensor method according to claim 12, further comprising a variation of the distance between the lens (32) and the transmitter-receiver device (30).

14. The level sensor method according to claim 12 or claim 13, further including a communication by a communication board (34) between the level sensor and a terminal to transmit the distance calculation information coming from the electronic board.