Electric field detector

Abstract

The electric field detector (20) comprises an electromechanical oscillator, part of which comprises a piezoelectric element (1), a frequency measuring device (4) coupled to the electromechanical oscillator to measure the oscillation frequency, and an electric mask assembly (5). The electric mask assembly is positioned near the piezoelectric element (1) so that, during use of the electric field detector, the piezoelectric element vibrates and moves relative to the electric mask assembly. A variable portion of the piezoelectric element is therefore exposed to the electric field to be measured. Changes in the oscillation frequency (f) form an electric field measurement.

Description

Technical Field

[0001] The present invention relates to an electric field detector.

Background Art

[0002] An electric field detector including at least one electrode and a movable mask is known. The movable mask is made of a conductive material, disposed in front of one or more electrodes, and partially masks the one or more electrodes from the electric field to be measured. Thus, one or more variable portions of this (one or more) electrode are exposed to the electric field to be measured and generate a current in one or more connection portions that link the (one or more) electrodes to a current detector. The detected current constitutes a measured value of the electric field. However, such detectors are bulky, expensive, and energy-consuming, and thus are not suitable for many applications, particularly for applications for measuring electrostatic fields mounted on aircraft, drones, or satellites.

[0003] To overcome these drawbacks, recently, an electric field detector based on a silicon MEMS ("Micro Electro-Mechanical Systems") device has been developed. However, if the electric field is used to vibrate the MEMS device during each measurement, a bias occurs in the measurement result. In addition, the measurement proceeds by evaluating a certain amount of charge, which requires the use of a high-resolution analog-to-digital converter. Such converters are expensive in themselves and cause significant energy consumption.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention is to propose a new electric field detector that is small, inexpensive, low-power, and has accurate and reliable measurement results.

Means for Solving the Problems

[0005] To at least partially achieve this or other objectives, a first aspect of the present invention proposes an electric field detector including the following: An electromechanical oscillator, at least a part of which is composed of a piezoelectric element intended to vibrate at an oscillation frequency during the use of the electric field detector, and A frequency measuring device coupled to the electromechanical oscillator for measuring the oscillation frequency, and An electric mask assembly disposed near the piezoelectric element without contacting the piezoelectric element, such that during the use of the electric field detector, the piezoelectric element moves by vibrating with respect to the electric mask assembly as a result.

[0006] According to the present invention, further, the electric mask assembly is arranged such that during the use of the electric field detector, the portion of the piezoelectric element exposed to the electric field to be measured changes during each oscillation of the electromechanical oscillator while being restricted by this electric mask assembly. The electric field to be measured acts on the variable exposed portion of the piezoelectric element during the use of the electric field detector, generating a change in the oscillation frequency measured by the frequency measuring device. Thereby, the oscillation frequency forms the electric field strength measurement result.

[0007] Therefore, the present invention solves the drawbacks of the detectors of the prior art by using a piezoelectric oscillator. Such oscillators are actually inexpensive, lightweight, and small. Furthermore, their use does not require generating an electric field that may bias the measurement results.

[0008] Generally, in the present invention, the material of the piezoelectric element can have various chemical compositions. In particular, this piezoelectric element is a part of crystalline quartz, a part of aluminum nitride (AlN), a part of gallium phosphate (GaPO4), or a chemical formula La 3 Ga 5.5 Ta 0.5 O 14It may also be a part of a langatate crystal corresponding thereto, where La represents the lanthanum element, Ga represents the gallium element, Ta represents the tantalum element, and O represents the oxygen element. Such a crystalline material is available in the form of a thin slice, i.e., a "wafer", which can be chemically etched to obtain a piezoelectric element having a desired shape for this element.

[0009] Again generally, the piezoelectric element can have various shapes suitable for generating the vibrations necessary for the operation of the oscillator. Thus, in various possible embodiments of the present invention, the piezoelectric element can comprise one of the following structures: A beam intended to vibrate by bending during use of the electric field detector, in particular, a beam having a fixed first end and another free end on the opposite side of the first end, Two parallel beams each intended to vibrate by bending during use of the electric field detector, both beams being connected to each other by their respective first ends in each of the two beams, and the other ends of each beam on the opposite side of the first end of the same beam being free, such two parallel beams, Two parallel beams each intended to vibrate by bending during use of the electric field detector, both beams being connected to each other on the one hand by their respective first ends of the two beams, and on the other hand being connected to each other by their other ends on the opposite side of the first end, such two parallel beams.

[0010] The electrical mask assembly can comprise at least one metal part, and the edge of this metal part is arranged in front of the piezoelectric element so as to partially mask the piezoelectric element with respect to the electric field to be measured at at least one instant during each oscillation. However, preferably, this electrical mask assembly may comprise two metal parts, and these metal parts are such that when the electric field detector is oriented so that both metal parts are perpendicular to the electric field to be measured, symmetrically on one side and the opposite side of the piezoelectric element, they are two metal parts that generate the same partial mask of the piezoelectric element with respect to the electric field to be measured.

[0011] Generally, an electromechanical oscillator may comprise, in addition to a piezoelectric element, at least one electronic amplifier electrically connected to an electrode in contact with the piezoelectric element, and as a result, may form a loss-compensating oscillator loop structure. In such a case, in order to transmit an excitation voltage to the piezoelectric element during the use of the electric field detector, one of the electrodes can be electrically connected to the output of the electronic amplifier, and in order to detect the response electrical current generated from the piezoelectric element, the other of the electrodes can be connected to the input of a current detection system. Then, the output of the current detection system is connected to the input of the electronic amplifier in order to form a loop structure.

[0012] Advantageously, one of the electrodes, preferably each electrode, can be arranged on the piezoelectric element at a position that is masked by the electrical mask assembly with respect to the electric field to be measured during the use of the electric field detector. Thus, the measurement bias that can be caused by each electrode can be reduced or eliminated.

[0013] Finally, a second aspect of the present invention proposes an electric field detection assembly comprising two electric field detectors, each being an electric field detector according to the first aspect. These two electric field detectors have the same piezoelectric element and different respective electrical mask assemblies. Thus, when the electric field to be measured is non-zero (not zero, non-zero), the electric field to be measured generates changes in oscillation frequencies that are different between the two electric field detectors. Further, the electric field detection assembly comprises a subtraction unit, which is arranged to characterize the difference between the oscillation frequencies measured by the respective frequency measuring devices of both electric field detectors. Next, this difference forms another electric field strength measurement result, which is less sensitive to ambient temperature fluctuations than the measurement results separately sent by each of the two electric field detectors. In fact, since the piezoelectric elements of both electric field detectors are the same, fluctuations in the ambient temperature cause a shift in the oscillation frequency that is the same for both electric field detectors when there is no electric field to be measured. However, when the electric field to be measured is non-zero, it creates changes in oscillation frequencies that are different between the two electric field detectors due to their different respective electrical mask assemblies. The subtraction unit then makes it possible to eliminate the contribution from fluctuations in the ambient temperature from the electric field measurement result.

[0014] The features and advantages of the present invention will become more apparent in the following detailed description of some non-limiting exemplary embodiments with reference to the accompanying drawings.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2a

Figure 2b

Figure 2c

Figure 2d

Figure 2e

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

Mode for Carrying Out the Invention

[0016] For clarity, the dimensions of the elements shown in these figures do not correspond to the actual dimensions or the actual dimensional ratios. Furthermore, some of these elements are only symbolically represented, and the same reference numerals shown in different figures are the same or indicate elements having the same function.

[0017] According to FIG. 1, the electric field detector 20 according to the present invention includes an electromechanical oscillator, a frequency measuring device, and an electric mask assembly. The electric mask assembly, which is not visible in FIG. 1, will be described with reference to FIG. 2a. The electromechanical oscillator includes a piezoelectric element 1 having a pair of electrodes 61 and 62, which applies an excitation voltage V X to the piezoelectric element 1 and collects a response signal generated by this piezoelectric element 1, for example, a response current I R . In a known method, the electromechanical oscillator is formed by a loop structure including, in addition to the piezoelectric element 1, a detection system for detecting the response current I R indicated by reference numeral 2 and an amplifier indicated by AMPL. indicated by reference numeral 3. The current detection system 2 may be formed based on an operational amplifier 21 having an inverting input, a non-inverting input, and an output, and an electrical resistor 22. The non-inverting input of the operational amplifier 21 is connected to the ground of the electric field detector 20, the inverting input is connected to the electrode 62 that sends out the current I R from the piezoelectric element 1, and the resistor 22 is connected between the inverting input and the output of the operational amplifier 21. At this time, the current detection system 2 measures the response current IR Outputs a voltage proportional to it. Other electrical structures are possible for the current detection system 2 and are known to those skilled in the art. The output of the current detection system 2 is connected to the input of the amplifier 3, and the output of the amplifier 3 is the excitation voltage V applied to the electrode 61 X to supply. Such a loop structure makes it possible to compensate for energy losses and to satisfy the phase conditions necessary for the existence of self-oscillation. These oscillations cause the vibration of the piezoelectric element 1, and their frequencies are the resonance frequencies of the electromechanical oscillator when used in an open-loop circuit and in a sine-wave drive mode. The frequency measuring device is indicated by the reference numeral 4 and designated as FREQ. The frequency measuring device may be connected to the output of the amplifier 3 in parallel with the electrode 61. It may be a commercially available standard electronic frequency meter.

[0018] The piezoelectric element 1 may be a crystal quartz tuning fork as shown in Fig. 2a. Thus, the piezoelectric element 1 is composed of two mutually parallel and spaced beams 11 and 12 that are rigidly connected to each other only by one of their respective ends via a fixed base portion 10. Such a beam model is said to have one free end and one embedded end. The dashed contours show the bending deformations of both beams 11 and 12. Basically, the ends of each beam 11, 12 rigidly connected to the base portion 10 correspond to the vibration nodes of the piezoelectric element 1. The longitudinal directions of the beams 11 and 12 are parallel to the crystallographic direction Y of the crystal quartz used to form the piezoelectric element 1, and the plane of the tuning fork is perpendicular to the crystalline direction X. Fig. 2a also shows an electrical mask assembly 5 composed of two metal plates 51 and 52. The reference symbol E indicates the measurement target electric field passing through the beams 11, 12 of the piezoelectric element 1 at the sides of the beams protruding beyond the metal plates 51, 52. For proper use of the electric field detector 20, the electric field E is oriented to be substantially perpendicular to the metal plates 51 and 52.

[0019] Figures 2b and 2c show a first possible arrangement for electrodes 61 and 62 on the piezoelectric element 1. The electrodes are arranged longitudinally on each of the beams 11, 12 on the beam surface in the same plane along the entire length or substantially the entire length of the beam, and with respect to the edge of the beam closest to the central axis of the tuning fork. Thus, electrode 61 has two electrode segments, with one segment arranged on beam 11 and the other segment arranged on beam 12, on the same side of the tuning fork. Similarly, electrode 62 also has two electrode segments, with one segment arranged on beam 11 and the other segment arranged on beam 12, on the other side of the tuning fork as seen from electrode 61. The electrodes 61 and 62 arranged in this way cause the elongation or contraction of the inner edges of the two beams 11 and 12, which are identical at each instant of vibration. All the electrode segments arranged in this way are masked by the metal plates 51, 52 with respect to the electric field E to be measured.

[0020] Figures 2d and 2e show a second possible arrangement for electrodes 61 and 62. Here, the electrodes are limited to the portions of each of the beams 11, 12 close to the base portion 10, and each of the electrodes 61, 62 comprises two pairs of electrode segments arranged and connected so as to generate electric fields facing opposite sides between the inner and outer sides of each beam at the feet of each of the beams 11, 12, although each of the electrodes 61, 62 is still symmetric between the two beams 11, 12. Such a mode of piezoelectric excitation of the tuning fork causes a "hinging" of each of the beams 11, 12 with respect to the base portion 10, and then each beam vibrates by bending from this hinge.

[0021] Figure 3 shows another possible model of the piezoelectric element 1. The piezoelectric element 1 is still composed of two identical and parallel beams 11 and 12, but the beams 11 and 12 are here connected to each other by their two respective ends and connected to two fixed base parts 10’ and 10”. Such a model of the piezoelectric element is said to be hinged-hinged in the jargon of those skilled in the art. Each of the beams 11, 12 still vibrates by bending in a direction parallel to the plane of the piezoelectric element 1 such that the instantaneous bending directions of the two beams face opposite directions and the absolute values of the instantaneous deflection values of the two beams are the same. In this model of the piezoelectric element 1 cited as another possible model, the electrodes 61 and 62 can have a configuration similar to that of FIGS. 2b and 2c on both of the beams 11 and 12, but the electrodes 61 and 62 are limited to the central portion along the length of the beam.

[0022] Other models of the piezoelectric element 1 are possible, in particular a model having a single vibrating beam, one end of which is free and the other end of which is called “embedded” and firmly connected to the fixed base part of the element. In known methods, piezoelectric elements such as those described above can be manufactured by chemical etching or reactive ion etching from a crystalline quartz wafer.

[0023] According to FIG. 4, for example, the piezoelectric element 1 in FIGS. 2a to 2c is inserted between two electric masks 51 and 52, and the electric masks 51 and 52 are arranged parallel to each other on two opposite sides of the piezoelectric element 1 but not in contact with each other. Both the electric masks 51 and 52 form the electric mask assembly 5. The electric masks 51 and 52 are symmetric to mask a part of the piezoelectric element 1 from the external electric field E. This external electric field E is perpendicular to both masks 51 and 52 during the optimal use of the electric field detector 20. In other words, the two metal plates 51, 52 are overlapped on a common projection plane parallel to these plates. Also, both metal plates 51, 52 are sized to mask a limited portion of the piezoelectric element 1, and this limited portion changes with each vibration. In the case of the model of the piezoelectric element 1 shown in FIGS. 2a and 3, both metal plates 51 and 52 can mask the respective portions arranged toward the center of the piezoelectric element in the beams 11, 12, and the edges of these plates are parallel as shown in the figure and are overlapped on the central region in the longitudinal direction of the beam. In this way, only the longitudinal portions near the outer edges of each beam 11, 12, that is, the longitudinal portions near the surface on the opposite side of the other beam among the plurality of surfaces of each beam, are exposed to the electric field E. In addition, this exposed portion has a volume that changes according to the instantaneous state of the vibration of the beam. In some possible embodiments of the metal plates 51, 52, the metal plates may be composed of metal layer portions made of silver (Ag) or gold (Au) deposited on a flat base material such as a glass plate, for example. The metal plates 51, 52 are electrically connected to each other and may remain at a floating potential or may be connected to a potential reference terminal. In some simplified embodiments of the present invention, the electric mask assembly 5 may include only a single metal plate on only one of the side surfaces of the piezoelectric element 1.

[0024] Here, referring to FIG. 4, the operating principle of the electric field detector 20 will be described. The excitation voltage V X generates a distribution of stress in the piezoelectric element 1 that causes the vibration of the piezoelectric element 1. In the absence of an external electric field, the self-oscillation of the electromechanical oscillator is at a frequency value f which is its natural oscillation frequency0 has this value f 0 mainly depends on the dimensions of the piezoelectric element 1, its intrinsic parameters, the values of the elastic parameters of the piezoelectric material, and the electrical parameters of the entire oscillator. The intrinsic oscillation frequency value f 0 of such an electromechanical oscillator is known to those skilled in the art. In particular, during oscillation at this intrinsic oscillation frequency value f 0 , the excitation voltage V X is in quadrature with respect to the deformation of the piezoelectric element 1. In fact, the excitation voltage V X exactly compensates for the dissipation losses such as the viscous friction losses of the piezoelectric element 1 in the ambient gas. However, such losses are proportional to the instantaneous deformation rate of the piezoelectric element 1. More precisely, the excitation voltage V X generates a piezoelectric excitation force represented as F exci that maintains the vibration of the piezoelectric element 1 in the steady state of oscillation in each of the beams 11, 12. The intrinsic oscillation frequency value f 0 can be experimentally measured by the frequency measuring device 4 when no external electric field is present.

[0025] The external electric field denoted by E is the electric field to be measured. When the electric field E is not zero, the electric field E passes through the portion of the piezoelectric element 1 that is not masked by the electrical mask assembly 5. This unmasked portion, i.e., the portion exposed to the electric field E, may be divided between both beams 11 and 12 as in the illustrated embodiment. In this unmasked portion, the electric field E causes an additional piezoelectric force represented as F piezo that is proportional to the instantaneous fraction of the piezoelectric element 1 passed through by the electric field E. Therefore, this additional piezoelectric force F piezo is proportional to the instantaneous deformation of the piezoelectric element 1.

[0026] In the presence of the electric field E to be measured, the piezoelectric excitation force F X generated by the excitation voltage V exci in the piezoelectric element 1 is much larger than the additional piezoelectric force F piezo . For this reason, the piezoelectric excitation force F exciThe phase difference value with the deformation of the piezoelectric element 1 does not change much. As a result, the forces F piezo and F exci are both in a phase perpendicular to each other. Thanks to this right-angle phase correlation, the change in the value caused by the additional piezoelectric force F piezo in the oscillation frequency of the electromechanical oscillator in the presence of the electric field E is maximized, while all other parameters of the electromechanical oscillator remain unchanged. And, ΔF = (F piezo / F exci )·f 0 / (2·Q), where ΔF is the variation in the oscillation frequency caused by the electric field E, and Q is the quality factor of the piezoelectric element 1 when used as an open-loop resonator and in the sine-wave drive mode. The variation Δf is equal to the difference f - f 0 , where f is the oscillation frequency measured by the frequency measuring device 4 in the presence of the electric field E. The variation in the oscillation frequency Δf is proportional to the electric field E, Δf = K·E, and the proportionality coefficient K depends in particular on the geometric and electromechanical characteristics of the piezoelectric element 1, as well as the geometric characteristics of the mask assembly 5. The proportionality coefficient K can be determined by digital modeling of the electromechanical oscillator or by calibration of the electric field detector 20. For the piezoelectric element 1 made of single-crystal quartz and following FIG. 2a, K is when both of the beams 11 and 12 have a length L equal to 3 mm (millimeters), a width e in the plane of the tuning fork equal to 200 μm (micrometers), and a thickness h measured perpendicular to the plane of the tuning fork equal to 30 μm, and when both of the beams 11 and 12 are separated by a distance d equal to 100 μm, it is equal to about 4 μHz / (V / m) (microhertz per volt per meter). Therefore, the oscillation frequency value f sent by the frequency measuring device 4 constitutes the measured value of the electric field E, and E = (f - f 0 ) / K.

[0027] However, the natural oscillation frequency f 0can vary according to the temperature of the piezoelectric element 1, i.e., the ambient temperature at which the electric field detector 20 is used. The electric field detector 20 as described above cannot separate the contribution of the variation in the natural oscillation frequency f 0 due to the ambient temperature variation within the variation of the oscillation frequency f from the contribution generated by the electric field E to be measured. The detection assembly described here with respect to FIG. 5 makes it possible to remove the thermal contribution that affects the natural oscillation frequency f 0 . As a result, the measurement result sent by such a detection assembly characterizes only the electric field E to be measured, and this result is the same or substantially the same regardless of the ambient temperature. Such an improvement can be particularly beneficial when the ambient temperature can vary significantly, for example, when mounted on a satellite.

[0028] According to FIG. 5, the detection assembly for the electric field E is generally denoted by reference numeral 30 and includes two electric field detectors 20a and 20b that respectively follow the electric field detector 20 of FIG. 1. These two electric field detectors 20a and 20b are identical to each other except for their electrical mask assemblies. In particular, both the electric field detectors 20a and 20b have piezoelectric elements 1a and 1b that are identical and identically oriented, and each piezoelectric element can be of the single-crystal quartz tuning fork type as shown in FIG. 2a. Therefore, these piezoelectric elements have the same natural oscillation frequency f 0 , and this natural oscillation frequency f 0 varies in the same way with the ambient temperature for both the electric field detectors 20a and 20b. These two piezoelectric elements 1a and 1b are fixed and arranged close enough to each other within the detection assembly 30 to be exposed to the same electric field E to be measured. On the other hand, both the electric field detectors 20a and 20b have different electrical mask assemblies, and as a result, the coefficient K defined above has two different values, i.e., K a for the electric field detector 20a and K b for the electric field detector 20b. References 4a and 4b denote respective frequency measuring devices for measuring the oscillation frequencies of the electric field detectors 20a and 20b. Therefore, in the presence of the electric field E to be measured, the frequency measuring device 4a measures a first oscillation frequency value fa = f 0 + K a · E is provided, and the frequency measuring device 4b provides the second oscillation frequency value f b = f 0 + K b · E. These two values are transmitted to the subtraction unit 21, and the subtraction unit is represented as DIFF., and the difference value f a - f b =(K a - K b )· E is calculated. This difference value constitutes a new measured value of the electric field E and does not depend on the natural oscillation frequencies f 0 of the electromechanical oscillators of the two electric field detectors 20a and 20b. Therefore, this measured value no longer depends on the ambient temperature via this natural oscillation frequency f 0 . The residual dependence of the difference f a - f b on the ambient temperature can still occur through the coefficients K a and K b , but the residual dependence is smaller than the separate variations of the oscillation frequencies f 0 , f a and f b as functions of temperature.

[0029] According to the first possibility, the electric mask assembly of the electric field detector 20b indicated by the reference numeral 5b can be selected to have dimensions and positions that completely and continuously mask the piezoelectric element 1b of the electric field detector 20b during variations with respect to the electric field E. Therefore, the electric field detector 20b is not sensitive to the electric field E, the coefficient K b is 0, and the frequency f b measured by the frequency measuring device 4b is always equal to the natural oscillation frequency f 0 . As described with reference to FIGS. 2A to 4, the electric mask assembly of the electric field detector 20a indicated by the reference numeral 5a partially masks the corresponding piezoelectric element 1a. FIG. 6A shows such a configuration of the electric mask assembly 5a (or 5b) with respect to the piezoelectric element 1a (or 1b) in the electric field detector 20a (or 20b). And the measurement result sent out by the subtraction unit 21 with respect to the electric field E is f a - f 0 = Ka ·becomes E.

[0030] According to another possibility, the electrical mask assembly 5b of the detector 20b can mask a limited portion of the piezoelectric element 1b of the electric field detector 20b, and this portion is complementary to the portion masked by the electrical mask assembly 5a of the electric field detector 20a with respect to the piezoelectric element 1a of the electric field detector 20a. FIG. 6b corresponds to FIG. 6a in the case of such another configuration. Here, K b =-K a and the measurement result sent by the subtraction unit 21 with respect to the electric field E is f a -f b =2·K a ·E.

[0031] It is understood that the present invention may be reproduced while modifying secondary aspects of the embodiments detailed above and still retaining at least some of the cited effects. In particular, piezoelectric elements having shapes different from those shown in FIGS. 2a and 3 may be used. Further, although different from those described, electronic modules having equivalent functions may be used instead of those described.

Claims

Claim 1 An electric field detector (20), at least a part of which is composed of a piezoelectric element (1) intended to vibrate at an oscillation frequency during use of the electric field detector, an electromechanical oscillator, a frequency measuring device (4) coupled to the electromechanical oscillator for measuring the oscillation frequency, an electric mask assembly (5) disposed near the piezoelectric element (1) without contacting the piezoelectric element, and as a result, the piezoelectric element moves by vibrating with respect to the electric mask assembly during use of the electric field detector, an electric mask assembly (5), having,[[]] furthermore, the electric mask assembly (5) is arranged such that a portion of the piezoelectric element (1) exposed to the electric field to be measured (E) during use of the electric field detector (20) changes during each oscillation of the electromechanical oscillator while being restricted by the electric mask assembly, the electric field to be measured (E) acts on the variable portion of the piezoelectric element (1) exposed during use of the electric field detector (20), thereby generating a change in the oscillation frequency (f) measured by the frequency measuring device (4), and the oscillation frequency forms an electric field strength measurement result. An electric field detector (20). Claim 2 The piezoelectric element (1) is a part of crystalline quartz, a part of aluminum nitride, a part of gallium phosphate, or a chemical formula La ３ Ga ５．５ Ta ０．５ O １４ The electric field detector (20) according to claim 1, characterized in that it is a part of a crystal having Claim 3 The piezoelectric element (1) includes a beam intended to vibrate by bending during use of the electric field detector, in particular, a beam having a fixed first end and another free end on the opposite side of the first end, alternatively, the piezoelectric element includes two parallel beams (11, 12) each intended to vibrate by bending during use of the electric field detector (20), and both beams are connected to each other by respective first ends in each of the two beams, and the other end of each beam on the side opposite to the first end of the same beam is free, alternatively, the piezoelectric element (1) includes two parallel beams (11, 12) each intended to vibrate by bending during use of the electric field detector (20), and both beams are connected to each other by respective first ends of the two beams on one hand, and on the other hand, are connected to each other by respective other ends of the two beams on the side opposite to the two first ends. The electric field detector (20) according to claim 1 or 2, characterized in that Claim 4 The electric mask assembly (5) comprises at least one metal part, and an edge of the metal part is arranged in front of the piezoelectric element (1) so as to partially mask the piezoelectric element with respect to the electric field to be measured (E) at at least one moment during each oscillation, and is characterized in that the electric field detector (20) according to any one of claims 1 to 3.

5. The electric mask assembly (5) comprises two metal parts (51, 52), and when the electric field detector is oriented such that the two metal parts are perpendicular to the electric field to be measured, the two metal parts symmetrically generate the same partial mask of the piezoelectric element (1) with respect to the electric field to be measured (E) on one side and the opposite side of the piezoelectric element, and is characterized in that the electric field detector (20) according to claim 4.

6. The electromechanical oscillator comprises, in addition to the piezoelectric element (1), at least one electronic amplifier (3) electrically connected to electrodes (61, 62) in contact with the piezoelectric element, and as a result, forms a loss compensation oscillator loop structure, and is characterized in that the electric field detector (20) according to any one of claims 1 to 5.

7. One of the electrodes (61, 62) is electrically connected to the output of the electronic amplifier (3) in order to transmit an excitation voltage (V Ｘ ) to the piezoelectric element (1) during use of the electric field detector. The other of the electrodes is connected to the input of a current detection system (2) for detecting the response current (I Ｒ ), generated by the piezoelectric element The output of the current detection system is connected to the input of the electronic amplifier, and is characterized in that the electric field detector (20) according to claim 6.

8. One of the electrodes (61, 62) is arranged on the piezoelectric element (1) at a position of the piezoelectric element masked by the electric mask assembly (5) with respect to the electric field to be measured (E) during use of the electric field detector, and is characterized in that the electric field detector (20) according to claim 6 or 7.

9. An electric field detection assembly (30), comprising two electric field detectors (20a, 20b), each of which is an electric field detector according to any one of claims 1 to 8. The two electric field detectors each have the same piezoelectric elements (1a, 1b) and different electric mask assemblies (5a, 5b), and as a result, when the electric field to be measured is not 0, the electric field to be measured (E) generates a change in the oscillation frequencies (f ａ , f ｂ ) that is different between the two electric field detectors. Furthermore, the electric field detection assembly (30) includes a subtraction unit (21) arranged to characterize the difference between the oscillation frequencies (f ａ , f ｂ ) measured by the frequency measuring devices (4a, 4b) of both electric field detectors (20a, 20b), and the difference forms a measurement result of another electric field (E) intensity, and this result is less sensitive to ambient temperature variations than the measurement results separately sent by each of the two electric field detectors. An electric field detection assembly characterized by this.

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