Voltage measurement method and apparatus

Abstract

A method (100) for measuring voltage using a microelectromechanical system (MEMS) comprises a sample mass (110) supported above a substrate by a mechanical spring element (120) so as to be movable relative to the substrate along a vibration direction (x), a trimming electrode (130) adapted to generate an electrostatic force on the sample mass (110) when a voltage is applied thereto, the electrostatic force counteracting a mechanical spring force generated by the spring element (120) when the sample mass (110) is deflected along the vibration direction (x), a drive electrode (140) adapted to move the sample mass (110) along the vibration direction (x), and a readout electrode (150) adapted to measure the frequency of vibration of the sample mass (110) thus generated: applying a voltage to be measured to the trimming electrode (130), determining the magnitude of the voltage to be measured from the measured vibration frequency of the sample mass (110), and detecting a change in the voltage to be measured based on a change in the measured vibration frequency.

Description

Technical Field

[0001] The present invention relates to a method for measuring voltage by a microelectromechanical system and such a microelectromechanical system.

Background Art

[0002] A reference voltage source is used to pre-determine a voltage for performing further operations in various electronic applications. For example, the reference voltage is used in an analog-to-digital converter that samples an analog signal. Other parameters used in corresponding electronic components, such as voltage values and electrical variables, are also set or calculated based on the reference voltage.

[0003] Particularly, in the case of an acceleration sensor or an angular velocity sensor designed as a microelectromechanical system (MEMS), a reference voltage is required to set the driving voltage and / or the readout voltage used to a predetermined value or a determinable value in advance. For example, the measurement accuracy of an acceleration sensor generally scales quadratically with respect to the vibrating mass of the sensor and the voltage applied between its driving / readout electrodes. The so-called scale factor converts a measurable change in capacitance or charge caused by the deflection of the sample mass into the actual acceleration of interest and thus depends quadratically on this driving readout voltage. Since this voltage is generated or set based on the reference voltage, the scale factor depends quadratically on the magnitude of the reference voltage.

[0004] High-performance components such as high-precision acceleration sensors and angular velocity sensors are required to be stable over a long period of time, that is, the calculation results and measurement results are of the same quality over a very long period such as 10 years or more, and particularly, there is no temporal drift, that is, no continuous increase or decrease.

[0005] Here, the scale factor of the acceleration sensor is allowed to have a deviation of less than 100 ppm per year, i.e., only one part in 100 million of the scale factor in the early stages of the product lifecycle, assuming that the operating and environmental conditions remain constant throughout the product lifecycle.

[0006] However, typical reference voltage sources can only achieve an accuracy of, for example, on the order of 50 ppm per year. Due to the quadratic dependence of the scale factor on the reference voltage, the scale factor will change by 100 ppm per year in this case. Considering the aging of other components as well, for a commonly implemented accelerometer, the drift in the scale factor, and consequently the drift in the measured value, will be at least 300 ppm per year. This also affects the measurement accuracy through the sensor's offset / bias, reaching values ​​of up to 50-100 μg, which is too large for a high-precision accelerometer without correction.

[0007] Inaccuracies in other electronic components that occur over time can be estimated in a similar manner. Here again, the temporal drift of the reference voltage is often the main cause of the overall component drift.

[0008] In this process, improving the accuracy of the reference voltage source is either impossible or only possible through complex methods. Furthermore, direct measurement of the reference voltage suffers from problems such as temporal drift similar to the reference voltage drift, as well as inherent measurement inaccuracies. [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, an object of the present invention is to provide a method for measuring a voltage, particularly a reference voltage, which has sufficient accuracy to detect long-term voltage drift. Another object of the present invention is to specify an apparatus capable of carrying out such a method. [Means for solving the problem]

[0010] This objective is achieved by the subject matter of the independent claim. Further advantageous developments are defined in the dependent claim.

[0011] In particular, the method for measuring voltage uses a micro-electromechanical system (MEMS). The MEMS has a sample mass mounted above the substrate by a mechanical spring element so that it can move relative to the substrate along the direction of vibration, and a trim electrode suitable for generating an electrostatic force on the sample mass when a voltage is applied, which counteracts the mechanical spring force generated by the spring element when the sample mass is deflected along the direction of vibration. It also has a drive electrode suitable for moving the sample mass along the direction of vibration and a readout electrode suitable for measuring the frequency of the vibration of the sample mass thus generated. The method includes the steps of applying a measurement voltage to the trim electrode, measuring the magnitude of the measurement voltage from the measured vibration frequency of the sample mass, and detecting the change in the measurement voltage based on the change in the measured vibration frequency.

[0012] Therefore, detection of the measured voltage is achieved by determining the vibration frequency of the vibration system. Since the vibration frequency can be determined with considerably more accuracy than the voltage, this already contributes decisively to the above objective. Furthermore, by applying the measured voltage to the trim electrode, it is achieved that the voltage has a significant effect on the vibration behavior of the sample mass. The voltage applied to the trim electrode effectively changes the spring constant of the vibration system. With proper design of the MEMS, particularly the design of the mechanical spring constant, it is possible to set an effective spring constant that is particularly advantageous for detecting frequency changes due to changes in the measured voltage. By applying the measured voltage to the trim electrode, the measurement accuracy can be further improved.

[0013] Advantageously, the measured voltage is the reference voltage, and its magnitude forms the basis for further measurement and / or calculation operations. This method further includes correcting further measurement and / or calculation operations by replacing the expected reference voltage with the measured reference voltage. Therefore, additional operations such as analog-to-digital conversion and determination of measurements by scale factor are performed at the measured voltage value, rather than the reference voltage specified for generating the reference voltage source. Similarly, the values ​​of variables (e.g., analog) derived from the reference voltage are updated or corrected based on the measured value of the reference voltage. This improves the results of further measurement and / or calculation operations.

[0014] By applying the measurement voltage to the trim electrode, 50% to 90%, preferably 60% to 80%, and more preferably 75% of the mechanical spring force can be compensated for. These compensation values ​​are particularly advantageous for the magnitude of frequency changes associated with changes in the measured voltage. This improves the accuracy of the measurement. The magnitude of the compensation can be achieved as soon as the magnitude of the measured voltage is known, through appropriate design of the MEMS, particularly the trim electrode and / or spring elements and the spring constants defined therein. In this way, particularly sensitive MEMS can be manufactured to specific voltage values.

[0015] This procedure can be performed especially when the MEMS is stopped, i.e., when there is no strong vibration or linear acceleration. This avoids interference from excessive movement. For example, this procedure can be performed every time an electronic component whose reference voltage is measured is activated. In particular, if this is an accelerometer, the MEMS can be expected to be stopped or nearly stopped. This ensures that a reliable value can be obtained for the voltage being measured.

[0016] A microelectromechanical system (MEMS) for measuring voltage includes a sample mass mounted above a substrate by a mechanical spring element so as to be able to move relative to the substrate along the direction of vibration; a trim electrode suitable for generating an electrostatic force on the sample mass when a voltage is applied; an electrostatic force that counteracts the mechanical spring force generated by the spring element when the sample mass flexes along the direction of vibration; a drive electrode suitable for moving the sample mass along the direction of vibration; and a readout electrode suitable for measuring the vibration frequency of the vibration of the sample mass thus generated. The MEMS further includes a control unit suitable for controlling the MEMS to perform the procedure described above.

[0017] By using such MEMS, the desirable effects described above can be obtained.

[0018] MEMS can be designed so that when a measurement voltage is applied to the trim electrode, a 1mV voltage change causes the resonance frequency of the sample mass to change within the range of 100ppm to 1000ppm. Therefore, MEMS are designed so that a relatively small change in the voltage applied to the trim electrode, for example, a 10V voltage of approximately 100ppm, leads to a significantly larger change in the resonance frequency than the stability fluctuation of the resonance frequency below 10ppm. This improves the accuracy of measuring changes in the resonance frequency and thus improves the accuracy of measuring changes in the voltage applied to the trim electrode.

[0019] In this process, the change in resonant frequency with voltage changes may not be linearly dependent on the deflection of the sample mass, and / or the resonant frequency may change with ambient temperature. Therefore, it is preferable for the control unit to take these dependencies into account through calibration when detecting the voltage under measurement. Both the magnitude of the vibration amplitude of the sample mass and the temperature changes of the MEMS components due to ambient temperature fluctuations can affect the mechanical and electrostatic spring constants generated by the trim electrodes. As a result, changes in the voltage of the trim electrodes cause the resonant frequency to change quite strongly for different deflections of the sample mass and / or temperature within the MEMS. This relationship is almost always not linear.

[0020] Therefore, the control unit is suitable for performing system calibration, for example, by determining known changes in the voltage of the trim electrode at different vibration amplitudes or temperatures, and the resulting changes in the resonant frequency. The relationships thus obtained can be directly used to correct measurements taken during operation to specific standard values ​​of vibration amplitude and / or temperature. Conversely, it is also possible to determine the temperature and / or vibration amplitude using known changes in voltage from measurements with respect to changes in resonant frequency. For example, calibration is not necessary if the vibration amplitude is kept constant or if measurements are taken only within a given temperature range.

[0021] MEMS is a system where, when a measurement voltage is applied to the trim electrode, the vibration system generated by the vibration of the sample mass is more than 1000. Quality Factor It can be designed to have this feature, which makes it particularly easy to measure changes in the resonant frequency.

[0022] The sample mass, spring element, trim electrode, drive electrode, and readout electrode can be evacuated in this process, for example, by enclosing them in a common vacuum housing. This eliminates air resistance in the system. Quality factor This leads to improvements, and ultimately to improved measurement accuracy.

[0023] An acceleration sensor for measuring acceleration can include MEMS as described above. At this time, the MEMS is suitable for measuring the acceleration acting on the acceleration sensor along the vibration direction of the sample mass by measuring the vibration frequency of the sample mass. Therefore, the vibration system of the MEMS is used not only to detect the change in the voltage applied to the trim electrode, but mainly to measure the change in vibration due to the acceleration applied to the sample mass. In this process, since the time constants are different, the two signals can be easily distinguished. The change in the measured voltage has a very long time constant, for example, several months or years, while the acceleration is of course a short-term effect, that is, in the range of seconds, minutes, or hours.

[0024] In this process, the measured voltage can be made equal to the reference voltage for determining the operating voltage applied to the drive electrode and / or the readout electrode. That is, the measured voltage becomes the voltage that determines the scale factor of the acceleration measurement. This makes it possible to detect and correct the change in the scale factor due to the drift of the reference voltage. At this time, it is particularly advantageous that it can be implemented with components available for acceleration measurement, and it is possible to prevent having an inventory of additional components and structures. In this way, a highly accurate, compact, and long-term stable acceleration sensor can be provided.

Brief Description of the Drawings

[0025] Hereinafter, the present invention will be further described with reference to the drawings. This description should be understood as purely exemplary. The present invention is defined only by the claims.

[0026] [Figure 1] It is a schematic diagram of a microelectromechanical system (MEMS) for measuring voltage. [Figure 2] It shows a schematic flowchart of the procedure for measuring voltage using MEMS. [Figure 3] It is a schematic diagram of MEMS for reference voltage measurement. [Figure 4]This is a schematic diagram of another MEMS device for measuring voltage. [Figure 5] This is a schematic diagram of an acceleration sensor consisting of MEMS for measuring drive voltage and / or readout voltage. [Figure 6] This is a schematic diagram of another MEMS device used for voltage measurement. [Figure 7] This is a schematic diagram of another MEMS device used for voltage measurement. [Modes for carrying out the invention]

[0027] Figure 1 is a schematic diagram of a micro-electromechanical system (MEMS) 100 for measuring voltage U. The MEMS 100 includes a sample mass 110, a mechanical spring element 120, and a trim electrode 130.

[0028] The sample mass 110 is mounted on the substrate by a mechanical spring element 120 so as to be movable relative to the substrate along the vibration direction x. In Figure 1, the substrate is parallel to the plane of the drawing, for example, below the shown sample mass 110. The sample mass 110 can be, in principle, any shape as long as the effects described below are obtained. Typically, the sample mass 110 has a planar spread with respect to the substrate; that is, the dimensions parallel to the substrate are much larger than the spread perpendicular to the substrate.

[0029] The spring element 120 is shown purely symbolically in Figure 1 and, in principle, can take any shape that can linearly guide the sample mass 110 along a specific vibration direction x. However, preferably, the spring element 120 allows the sample mass 110 to vibrate only along the vibration direction x. That is, the sample mass 110 is freely movable in the vibration direction x, except for the restoration of the spring force, and movement perpendicular to the vibration direction x is more strongly suppressed and therefore negligibly small. The spring element 120 is connected to the substrate via an anchor 125.

[0030] The voltage U can be applied to the trim electrode 130 relative to the sample mass 110 by, for example, supplying charge to the trim electrode 130 and / or the sample mass 110. In this case, the magnitude of the voltage U can be known.

[0031] As shown in Figure 1, the sample mass 110 may include a counter electrode 112. The voltage U can be applied only between the trim electrode 130 and the corresponding counter electrode 112. The counter electrode 112 can be made of the same material as the rest of the sample mass 110 and electrically connected. However, the counter electrode 112 can also be electrically isolated from the rest of the sample mass 110.

[0032] The voltage U generates an electrostatic force on the sample mass 110. The trim electrode 130 is designed or positioned relative to the sample mass 110 such that the electrostatic force counteracts the mechanical spring force generated by the spring element 120 when the sample mass 110 deflects along the vibration direction x. Therefore, for example, when the sample mass deflects to the right, if the spring element 120 moves the sample mass back to its initial position, i.e., to the left, a force is generated between the trim electrode 130 and the sample mass 110 in the direction of deflection, i.e., to the right. By changing the voltage U of the trim electrode 130, the effective spring constant of the entire vibration system can be changed depending on which portion of the mechanical spring force is compensated for by the electrostatic spring force. Similarly, if the voltage U is fixed within a specific range, a specific compensation ratio can be achieved by the configuration of the MEMS 100, i.e., the configuration of the sample mass 110, spring element 120, and / or trim electrode 130. The effective spring constant, or the difference between the mechanical spring force and the electrostatic force, naturally determines the resonant frequency of the vibration of the sample mass 110 along the vibration direction x.

[0033] The MEMS100 may have a drive electrode suitable for moving the sample mass 110 along the vibration direction x. The MEMS100 may also include a readout electrode suitable for measuring the vibration frequency of the vibration of the sample mass 110 thus produced. However, the sample mass 110 can also be vibrated by other means, such as the movement of the MEMS100 or coupling with other vibration systems. Therefore, the drive electrode is not absolutely necessary and is therefore not shown in Figure 1.

[0034] Since the vibration frequency can also be detected via the trim electrode 130, a special readout electrode can be omitted. For example, at a constant voltage U, the change in capacitance of the capacitor formed by the trim electrode 130 and the counter electrode 112 can be established through charge measurement. This allows the distance to be determined, and the vibration frequency can be determined by the passage of time. However, other readout methods are also possible. In this case, at least one trim electrode 130 functions as a readout electrode.

[0035] The MEMS100 further includes a control unit (not shown) suitable for controlling the MEMS100 to perform a procedure to measure the voltage U applied between the trim electrode 130 and the sample mass 110. The control unit can be formed on the substrate of the MEMS100 in this process. However, the control unit can also be located externally. The procedure performed by the MEMS100 is schematically summarized below with reference to Figure 2.

[0036] In S110, the measurement voltage U is applied to the trim electrode 130, which generates an electrostatic force on the sample mass 110, partially compensating for the mechanical spring force.

[0037] In S120, the magnitude of the measured voltage U is determined from the vibration frequency of the measured sample mass 110. Since the mechanical properties of the MEMS 100 are predetermined by the manufacturing process and are therefore known, it is possible to determine the effect of voltage U on the effective spring constant and, consequently, on the vibration frequency of the sample mass 110. Furthermore, it is possible to measure the vibration frequency both with and without voltage U applied to the trim electrode 130 while keeping other operating parameters constant. The magnitude of voltage U can also be estimated by comparing the measurement results.

[0038] In S130, the change in the measured voltage U is determined based on the measured change in frequency. In particular, small voltage changes in the millivolt range that occur over long periods, such as one or ten years, can be determined with higher accuracy by locating the change in vibration frequency than by directly measuring the voltage.

[0039] In this way, small changes in a voltage that is assumed to be constant can be accurately determined over a long period of time. Preferably, by applying a voltage U to the trim electrode 130, 50% to 90%, preferably 60% to 80%, and more preferably 75% of the mechanical spring force is compensated. As will be further described below, the MEMS 100 has sufficient sensitivity to changes in the measured voltage U with such parameter selection or such layout of the MEMS 100.

[0040] This procedure is preferably performed while the MEMS 100 is stopped, or when it is expected to be in a stopped state, such as when the MEMS 100 starts operating or when the device used with the measurement voltage U is being measured. In principle, this procedure is based on detecting changes in the effective spring constant that are reflected in the changes in vibration being performed. Since the movement of the MEMS 100, especially acceleration, can disturb these vibrations, operation in a stopped state is desirable to obtain reliable results. Otherwise, disturbances must be detected and corrected.

[0041] As schematically depicted in Figure 3, the measured voltage U can serve as a reference voltage, and its magnitude forms the basis for further measurement and / or calculation operations. In this process, the reference voltage U is necessary for the operation of electronic components 200 such as voltage converters, analog / digital converters, sensors, and, for example, acceleration sensors, and is generated by a reference voltage source 210. The electronic components 200 perform measurement and / or calculation operations based on the reference voltage U. For example, the reference voltage U can function as a reference or comparison value for various voltages and / or electrical variables used in the electronic components 200. As described above, the measurement results of the electronic component 200 configured as a sensor may also depend on the magnitude of the reference voltage. The MEMS 100, which also supplies the reference voltage U, can be used in this process as part of the electronic components 200 or as a separate component.

[0042] As symbolized by the dashed line in Figure 2, this procedure may optionally further include correcting additional measurement and / or calculation operations in S140 by replacing the expected reference voltage with the measured reference voltage U. This enables the electronic component 200 to operate stably over the long term based on the reference voltage.

[0043] Particularly preferred is a MEMS configuration in which, when a measurement voltage U is applied to the trim electrode 130, the resonant frequency of the vibration of the sample mass 110 changes by a value in the range of 100 ppm to 1000 ppm of its resonant frequency for every 1 mV voltage change. This enables particularly accurate and reliable measurement of the voltage U.

[0044] A schematic design of MEMS100 that can meet the above requirements is shown, for example, in Figure 4. All components are made of silicon, for example.

[0045] As shown in Figure 4, the sample mass 110 can be designed as a rectangular perforated pattern on which the trim electrodes 130 are placed. In this way, the trim electrodes 130 form a plate capacitor with the recessed sides of the sample mass 110 in a space-saving manner.

[0046] The sample mass 110 is symmetrically attached to the four upper corners of the substrate via spring elements 120 configured as bent bending beam springs. In this configuration, the bending beam springs extend perpendicular to the vibration direction x, allowing the sample mass 110 to vibrate in this direction, while movement in other directions is negligibly suppressed.

[0047] The vibration of the sample mass 110 is driven by a drive electrode 140 positioned transversely to the vibration direction x, which engages with a counter electrode 114 of the sample mass 110. The vibration parameters are read out via a trim electrode 130, which also functions as a read electrode 150. However, the drive electrode 140 can also function as a read electrode 150, or a separate read electrode 150 may be provided.

[0048] The force acting between the trim electrode 130 and the sample mass 110 is the electrostatic spring constant for vibrations of the sample mass, which is defined as follows: JPEG0007902346000001.jpg19168 Here, N is the number of trim electrodes, h is the height perpendicular to the substrate, L is the length parallel to the substrate and perpendicular to the vibration direction x, and d is the gap distance between the trim electrode 130 and the stationary sample mass 110.

[0049] As a result, the resonant frequency is determined by the effective spring constant keff: JPEG0007902346000002.jpg62168 Here, m represents the mass of the sample mass 110, and the mechanical spring constant km is given by the following equation: JPEG0007902346000003.jpg18168 Here, n is the number of spring elements, ESi is the modulus of elasticity of silicon, h is the height of spring element 120 perpendicular to the substrate, b is the width in the vibration direction x, and l is the length in the direction parallel to the substrate and perpendicular to the vibration direction x.

[0050] The sensitivity of the resonant frequency to changes in voltage U is as follows: JPEG0007902346000004.jpg36168 If a compensation factor β is introduced, then the following holds: β· k(m) = g· U(2).

[0051] Therefore, high sensitivity can be achieved, for example, by a relatively large voltage U or a large coefficient g, i.e., by the largest possible effective trim electrode area N·L·h with the smallest possible gap distance d. High sensitivity can also be achieved by a small mass m and a small mechanical spring constant k(m) with a sample mass of 110, i.e., a small width b and a large length l.

[0052] When the decomposable change in voltage is quantified as a fraction of the measured voltage U, dU = α·U, the relationship between the resulting frequency change df and the output frequency f is as follows: The relative frequency stability of JPEG0007902346000005.jpg30168 is approximately 10 ppm, and frequency changes of the order of 10 ppm in the output frequency cannot be immediately identified as a measured signal. Therefore, the following relationship is assumed to hold: JPEG0007902346000006.jpg17168 For example, if α = 50 ppm is selected, that is, if a very low value is already selected for the drift of the reference voltage within one year, the resulting compensation coefficient β is: If JPEG0007902346000007.jpg8168β is known, then considering that β·km = k(el) must be applied, the various parameters of MEMS100 in Figure 4 can be adjusted, resulting in the following specifications: Based on these specifications, the MEMS100 can, in principle, be adapted to any voltage U to be measured. That is, it is possible to configure the MEMS100 for measuring a specific reference voltage with a known range of values. In this way, a highly accurate voltmeter can be realized for slowly changing voltages.

[0053] Furthermore, when the measurement voltage U is applied to the trim electrode 130, the vibration system generated by the vibration of the sample mass 110 is 1,000 or more. Quality Factor Configuring MEMS100 to have this feature is useful in this process. This makes it particularly easy to measure the system's resonant frequency.

[0054] For this purpose, and to protect the components of MEMS100, MEMS100 may have a housing 160, which is symbolically depicted in Figure 4 as a dashed outline surrounding the MEMS components. The housing 160 consists, in particular, of the sample mass 110, spring element 120, trim electrode 130, drive electrode 140, and read electrode 150. The housing 160, and by extension the MEMS components within the housing 160, can be vented. This eliminates air resistance and the resulting damping, and improves the system. Quality Factor It will improve (further).

[0055] Of particular interest is the application of the above-mentioned technology to the acceleration sensor 400. A schematic representation of such an acceleration sensor 400 is shown in Figure 5.

[0056] The acceleration sensor 400 includes a MEMS 100, which is suitable for measuring the acceleration acting on the acceleration sensor 300 along the vibration direction x of the sample mass 110 by measuring the vibration frequency of the sample mass 110. For this purpose, the trim electrode 130 can be used as the readout electrode 150, as shown in Figure 4. However, it may be advantageous to detect the vibration of the sample mass 110 via a separate readout electrode 150. These can be placed on the side of the sample mass 110 together with the drive electrode 140, as shown in Figure 5. However, the side electrodes can be made to function as both drive and readout electrodes by time multiplexing.

[0057] Thus, if the trim electrode 130 can be connected separately to a voltage source, the acceleration sensor 400 configured according to the above considerations can also be used as a voltage measuring device. This makes it possible to realize additional functions with the acceleration sensor 400 that go beyond simple acceleration measurement.

[0058] As shown in Figure 5, the measured voltage U is preferably equal to the reference voltage used to determine the operating voltage applied to the drive electrode 140 or the readout electrode 150. In other words, the acceleration sensor 400 is equipped with a reference voltage source 410. The reference voltage generated by this reference voltage source 410 is applied to both the trim electrode 130 and the voltage generator 420. The voltage generator 420 generates the operating voltages for the drive electrode 140 and / or the readout electrode 150 from the reference voltage by scaling and / or modulating the reference voltage U, for example, in the form of sinusoidal modulation.

[0059] As mentioned above, the scale factor that converts measured vibration into acceleration is secondarily dependent on the operating voltage, and therefore on the reference voltage U. Therefore, by applying the reference voltage U to the trim electrode 130 and monitoring the effect of changes in the reference voltage U on the vibration system, the drift of the scale factor can be detected and corrected. In this way, a highly accurate and long-term stable acceleration sensor 400 can be provided.

[0060] The configuration of MEMS100 described above is purely illustrative. Numerous alternative configurations are possible, as long as the objective of producing a precisely measurable change in the vibration of the sample mass 110 by changing the voltage of the trim electrode 130 is achieved. The correct layout of such a sensor can be derived by those skilled in the art in a manner similar to the considerations above.

[0061] Figures 6 and 7 show examples of such alternative configurations. As depicted in Figure 6, the MEMS 100 may have a sample mass 110 configured primarily as a beam extending in the bending direction x. At both ends, the sample mass 110 is connected to a substrate via two spring elements 120 configured as a bent beam spring.

[0062] Furthermore, a row of drive electrodes 140 and read electrodes 150, configured as comb electrodes, is mounted on the substrate, and the same comb electrodes can be used as both drive electrodes 140 and read electrodes 150. The drive / read electrodes 140 and 150 mesh with counter electrodes 116, which are positioned on the sample mass 110 in the form of comb electrodes. By applying a voltage between the drive / read electrodes 140 and 150 and the counter electrodes 116, the sample mass 110 can be vibrated along the vibration direction x. The vibration can be determined, for example, by detecting the charge on the electrodes at a constant voltage, or by detecting the voltage at a constant charge (i.e., when the flow of current to the electrodes is interrupted).

[0063] The trim electrode 130 is mounted on the back side of the counter electrode 116 and resists the mechanical spring force when a voltage is applied. As already mentioned above, the trim electrode 130 can also function as a read electrode 130.

[0064] Figure 7 shows a schematic setup of MEMS100 that is essentially a replica of the MEMS100 setup shown in Figure 4. In this setup, two sample masses 110 share a centrally located pair of drive / readout electrodes 140, 150. In this region, the two sample masses 110 are connected by a connecting spring 122 that allows the two sample masses 110 to vibrate along the vibration direction x (and in opposite directions). Otherwise, each half of the MEMS100 setup in Figure 7 corresponds to the MEMS100 setup in Figure 4. Therefore, no further explanation is needed.

[0065] The two configurations in Figures 6 and 7, like many other possible configurations, also allow for the measurement of a voltage (in particular, a reference voltage) by applying a voltage to the trim electrode 130 and monitoring the resulting effect on the vibration behavior. Thus, those skilled in the art will see numerous possibilities for solving the problems described at the beginning within the claims.

Claims

1. A method for measuring voltage using a micro-electromechanical system (MEMS) (100), comprising: a sample mass (110) mounted above a substrate by a mechanical spring element (120) so as to be movable relative to the substrate along the vibration direction (x); a trim electrode (130) for generating an electrostatic force on the sample mass (110) when a voltage is applied, which generates an electrostatic force that counteracts the mechanical spring force generated by the spring element (120) when the sample mass (110) deflects along the vibration direction (x); a drive electrode (140) suitable for moving the sample mass (110) along the vibration direction (x); and a readout electrode (150) suitable for measuring the frequency of the vibration of the sample mass (110) thus generated; The steps include applying a measurement voltage (U) to the trim electrode (130), The steps include: measuring the magnitude of the measured voltage (U) from the vibration frequency of the measured sample mass (110); The process includes the step of detecting a change in the measured voltage (U) based on the change in the measured vibration frequency, The measured voltage (U) is a reference voltage, and its magnitude forms the basis for further measurement and / or calculation operations. A method further comprising the step of modifying the further measurement and / or calculation operation by replacing the expected reference voltage with the measured reference voltage.

2. The method according to claim 1, wherein 50% to 90% of the mechanical spring force is canceled out by applying the measurement voltage (U) to the trim electrode (130).

3. The method according to claim 1, wherein the method is performed while the micro-electromechanical system (MEMS) (100) is stopped.

4. A sample mass (110) is mounted above the substrate by a mechanical spring element (120) so that it can move relative to the substrate along the vibration direction (x), Suitable for generating an electrostatic force on the sample mass (110) when a voltage is applied, this electrostatic force cancels out the mechanical spring force generated by the spring element (120) when the sample mass (110) deflects along the vibration direction (x) via a trim electrode (130), A drive electrode (140) suitable for moving the sample mass (110) along the vibration direction (x), A readout electrode (150) suitable for measuring the frequency of the vibration of the sample mass (110) generated in this manner, A microelectromechanical system (MEMS) (100) for measuring voltage, comprising a control unit suitable for controlling the microelectromechanical system (MEMS) (100) to carry out the method according to claim 1.

5. A micro-electromechanical system (MEMS) (100) according to claim 4, wherein when the measurement voltage (U) is applied to the trim electrode (130) and the voltage changes by 1 mV, the resonant frequency of the vibration of the sample mass (110) changes in the range of 100 ppm to 1000 ppm.

6. The change in the resonant frequency associated with the change in the voltage does not depend linearly with respect to the deflection of the sample mass (110). and / or, the resonant frequency changes depending on the ambient temperature. The micro-electromechanical system (MEMS) (100) according to claim 5, wherein the control unit is suitable for taking into account these dependencies through calibration when detecting the measurement voltage (U).

7. The microelectromechanical system MEMS (100) according to claim 4, wherein the microelectromechanical system MEMS (100) is designed such that when a measurement voltage (U) is applied to the trim electrode (130), the vibration system generated by the vibration of the sample mass (110) has a quality factor of 1,000 or more.

8. The micro-electromechanical system (MEMS) (100) according to claim 4, wherein the sample mass (110), spring element (120), trim electrode (130), drive electrode (140), and readout electrode (150) are under vacuum.

9. A micro-electromechanical system (MEMS) (100) according to claim 4, A microelectromechanical system (MEMS) (100) suitable for measuring the acceleration acting on an acceleration sensor (400) along the vibration direction (x) of the sample mass (110) by measuring the vibration frequency of the sample mass (110), and an acceleration sensor (400) for measuring acceleration.

10. The acceleration sensor (400) according to claim 9, wherein the measured voltage (U) is equal to a reference voltage for determining the operating voltage applied to the drive electrode (140) and / or readout electrode (150).

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