Acceleration measurement device with improved zero bias stability

Abstract

The invention relates to an acceleration sensor (100), which comprises: a sensor mass (120), which is arranged above a substrate (120) by means of a spring element (130) and can move along a motion axis (x); a first fine-tuning electrode (140), which is connected to the sensor mass (120); and a sensor electrode (160), which is connected to the sensor mass (120). In addition, the acceleration sensor (100) also comprises: a second fine-tuning electrode (150), which is connected to the substrate (110) and corresponds to the first fine-tuning electrode (140); and a detection electrode (170), which is connected to the substrate (110) and corresponds to the sensor electrode (160). Here, the sensor electrode (160) and the detection electrode (170) are suitable for causing the sensor mass (120) to deflect along the motion axis (x), and measuring the deflection and a first electrostatic force applied by the sensor electrode (160) and the detection electrode (170) to the sensor mass (120). A second electrostatic force is generated on the sensor mass (120) by applying a fine tuning voltage between the first fine tuning electrode (140) and the second fine tuning electrode (150).

Description

Technical Field

[0001] The invention relates to a device and a method for measuring acceleration, wherein the measuring device has high zero bias stability. Background Art

[0002] Electrical acceleration sensors are used in various applications to measure acceleration. In this case, a mass component is usually arranged above a substrate by means of spring elements, the deflection of which is measured when an acceleration is applied. In addition to the forces exerted by the spring elements, various electrostatic forces also act on the sensor mass. In particular, in addition to the electrodes required for controlling the sensor mass and / or reading the applied acceleration, so-called fine-tuning electrodes can also be present, by adjusting the voltage applied between the fine-tuning electrodes, the effective spring constant of the system can be influenced. Thus, an electrostatic force can be exerted on the sensor mass via the fine-tuning electrodes, which reacts against the spring force and compensates for it in a first approximation (i.e. for small deflections of the sensor mass). The movement of the sensor mass takes place as if there were no effective return spring.

[0003] WO 2015 / 052487 A1 discloses an acceleration sensor in which a sensor mass can be brought into a position in which an electrostatic spring force coincides with a mechanical spring force.

[0004] WO 2016 / 120319 A1 discloses an acceleration sensor in which a fine-tuning voltage can be applied to compensate for a spring force acting on a sensor mass.

[0005] JP 2000 / 180180 A and US 2005 / 0001275 A1 disclose the use of fine-tuning electrodes in acceleration sensors.

[0006] Due to manufacturing tolerances, aging or environmental influences (e.g. temperature fluctuations), the individual subsystems that generate the various forces acting on the sensor mass may have different no-force positions. Thus, for example, the deflection of the sensor mass without spring forces may differ from the deflection without electrostatic forces applied by the fine-tuning electrodes and / or the control / readout electrodes. This results in a bias in the spring element during operation of the accelerometer, which is sensed by the control / readout electrodes and may distort the measurement result. This zero bias of the measurement must be corrected to obtain correct results.

[0007] Therefore, on the one hand it is advantageous to operate the acceleration sensor in such a way that the operating point of the sensor mass, i.e. the deflection of the sensor mass during operation, is as symmetrical as possible to the structure of the other sensor components in order to reduce the zero bias. Furthermore, it is desirable that the zero bias remains constant over a longer period of time in order to avoid corrections that are required for continuous adjustment of the zero bias. Summary of the invention

[0008] Therefore, the object of the present invention is to provide an acceleration sensor and an operating method thereof, so that the acceleration sensor is operated at an operating point with a zero bias that is as low as possible and as stable as possible.

[0009] This object is achieved by the subject matter of the independent claims.

[0010] The acceleration sensor may have: a sensor mass, which is arranged above the substrate by means of a spring element and can move along the motion axis; a first fine-tuning electrode, which is connected to the sensor mass; and a sensor electrode, which is connected to the sensor mass. In addition, the acceleration sensor may also have: a second fine-tuning electrode, which is connected to the substrate and corresponds to the first fine-tuning electrode; and a detection electrode, which is connected to the substrate and corresponds to the sensor electrode. Here, the sensor electrode and the detection electrode are suitable for causing the sensor mass to deflect along the motion axis and measuring the deflection and the first electrostatic force applied by the sensor electrode and the detection electrode to the sensor mass. When the sensor mass deflects along the motion axis, the spring element generates a spring force on the sensor mass. By applying a fine-tuning voltage between the first fine-tuning electrode and the second fine-tuning electrode, a second electrostatic force is generated on the sensor mass. By means of the sensor electrode and the detection electrode, the relationship between the first electrostatic force and the deflection of the sensor mass is determined for at least two different fine-tuning voltages, and a neutral point is determined therefrom for the following deflection, at which the corresponding first electrostatic force is the same for different fine-tuning voltages. The deflection of the sensor mass is then adjusted by the sensor electrodes and the detection electrodes about this neutral point.

[0011] In such an acceleration sensor, the sensor mass is subjected to three forces. The return spring force acts on the sensor mass via a spring element. The sensor electrodes and detection electrodes provided for controlling the sensor mass and / or reading the acting acceleration generate a first electrostatic force, while the fine-tuning electrodes generate a second electrostatic force. The combined effect of the spring force and the second electrostatic force can be considered as an effective spring force, which the first electrostatic force read out by the sensor must be equal to for the rest position of the sensor mass.

[0012] By varying the trimming voltage which results in the second electrostatic force, the strength of this effective spring force varies. Thus, in first order, ie for small deflections, a change in the trimming voltage results in a change in the effectively sensed spring constant of the combined system of spring element and trimming electrode.

[0013] For a specific trimming voltage, i.e. for a specific effective spring constant, the correlation of the first electrostatic force on the sensor mass, i.e. the force detected by the detection electrodes of the acceleration sensor, with the deflection of the sensor mass is determined. Thus, it is measured which force causes which deflection. For small deflections around the mechanical rest point of the spring element-sensor mass system, the relationship is linear, with a slope corresponding to the effective spring constant.

[0014] If the trimming voltage is now varied and the relationship between the effectively measured force and the deflection is measured again, another straight line with a different slope is obtained. At the intersection of the two straight lines, the second electrostatic force applied is the same for the different trimming voltages at the same deflection. In fact, in a first order approximation, i.e. for such deflections, in which the second electrostatic force generated by the trimming electrode varies linearly with the deflection, all the straight lines determined for the different trimming voltages intersect at a single point, which is hereinafter referred to as the "neutral point".

[0015] This neutral point is stable with respect to fluctuations in the applied trimming voltage, since such fluctuations do not affect the forces acting on the sensor mass. Therefore, the zero bias present at the neutral point is stable with respect to changes associated with the trimming electrodes.

[0016] In addition, the zero bias at the neutral point is particularly low, since the sensor mass is symmetrical to the sensor structure. This can be understood as follows. If Ff is used to denote the spring force, Fd is used to denote the first electrostatic force, and Ft is used to denote the second electrostatic force generated by the fine-tuning electrode, then in the force balance:

[0017] Fd=-Ff–Ft

[0018] At the neutral point n, the first electrostatic force must be the same for different trimming voltages U1 and U2, according to the definition of the neutral point. In addition, the sensor mass has a specific offset "n" at the neutral point. Therefore, at the neutral point, the force exerted by the spring element is also the same for different trimming voltages. It follows that the second electrostatic force must also be the same for different trimming voltages:

[0019]

[0020] Therefore, the sensor mass must be symmetrical about the fine-tuning electrodes at the neutral point, otherwise the condition Ft(U1,n)=Ft(U2,n) cannot be satisfied. If the fine-tuning electrodes are arranged as pairs of plate capacitors, for example, the second electrostatic force at the neutral point is even equal to zero, because all forces cancel each other out due to the symmetrical arrangement.

[0021] As a result, the acceleration sensor can be operated with a small and relatively stable zero bias as soon as the sensor mass has been brought into a starting position adjacent to the neutral point or even to the neutral point.

[0022] After the offset has been adjusted in this way with respect to the neutral point, the trimming voltage can be adjusted so that the second electrostatic force partially or completely compensates the spring force. In this case, the relationship between the first electrostatic force and the offset is approximately a horizontal line, i.e., substantially the same effective force is generated for all offsets. Therefore, a small position change from the neutral point will only result in a negligible change in the force measured by the sensor electrode and the detection electrode, as will a change in the trimming voltage, and thus in a negligible change in the zero bias. The zero bias stability is thus further improved.

[0023] The sensor electrodes and the detection electrodes can be divided into a first pair of sensor electrodes and the detection electrodes and a second pair of sensor electrodes and the detection electrodes. Here, the first pair and the second pair can be arranged at different positions along the motion axis, and the specified voltage can be applied alternately to the first pair of sensor electrodes and the detection electrodes and the second pair of sensor electrodes and the detection electrodes at a certain duty cycle. By changing the duty cycle, the first electrostatic force can be changed.

[0024] Since the sensor electrodes and the detection electrodes are spatially separated along the axis of motion, the first electrostatic force can be varied by alternately applying a single constant voltage to the spatially separated electrode pairs. For example, if the duty cycle is 50 / 50 when the first and second electrode pairs are configured identically, no first electrostatic force is generated. When the duty cycle changes in one direction, for example to 70 / 30, the first electrostatic force will be generated in one direction of the axis of motion, and when it changes in the other direction, for example to 30 / 70, the electrostatic force acts in the opposite direction. The strength of the force can therefore be adjusted by the number of times a pair of electrodes is pressed relative to another pair of electrodes within a specific time unit. In principle, this also enables an asymmetric structure of the electrode pairs, since a duty cycle that achieves an average forceless effect can always be found. Therefore, the effective electrostatic force or the second electrostatic force can be varied in a simple manner using a single specified voltage, making it easier to find a neutral point.

[0025] When a specified voltage is applied to the corresponding sensor electrodes and detection electrodes, the capacitance of the capacitor formed by the sensor electrodes and detection electrodes can be determined, and the offset of the sensor mass can be determined by the capacitance difference between the first pair of sensor electrodes and detection electrodes and the second pair of sensor electrodes and detection electrodes.

[0026] The relationship between the first electrostatic force and the deflection may be determined by the relationship between the applied duty cycle and the capacitance difference.

[0027] When a specified voltage is applied to each pair of sensor electrodes and detection electrodes, the charge flowing into the capacitor formed by these electrodes can be measured, for example by means of a corresponding amplifier. Since the applied voltage is known, the total capacitance of the electrodes to which the voltage is applied can be determined from this. Since the capacitance depends on the distance between the electrodes, the difference in the total capacitance of the two electrode pair groups is a measure of the offset of the sensor mass. Therefore, a corresponding calibration can deduce the offset from the measurement of the capacitance.

[0028] However, the relationship between the first electrostatic force and the deflection of the sensor mass can also be determined directly as the relationship between the duty cycle of the applied voltage and the capacitance difference. The neutral point is then understood as a specific capacitance difference at which the duty cycle is the same for different fine-tuning voltages.

[0029] For this purpose, the duty cycle can be varied for each trimming voltage and the capacitance difference can be determined for each duty cycle. To adjust the offset in the direction of the neutral point, the required duty cycle is adjusted so that for each different trimming voltage, the same capacitance difference is generated or strived for. In this way, the offset can be adjusted in a simple manner with respect to the neutral point without the need for calibration or conversion of measured values.

[0030] The voltage applied to the first fine-tuning electrode, the second fine-tuning electrode, the sensor electrode and / or the detection electrode can be adjusted automatically by the control circuit so that the offset is controlled with respect to the neutral point. For this purpose, for example, the duty cycle can be controlled so that a capacitance difference at the neutral point is achieved. Here, the required capacitance difference at the neutral point can be determined continuously by modulating the voltage applied to the fine-tuning electrodes. This enables automatic tracking of the sensor mass in the direction of the neutral point, even if this neutral point should be displaced over time or due to environmental influences.

[0031] The voltage applied to the first fine tuning electrode and the second fine tuning electrode can be automatically adjusted by another control circuit so that the second electrostatic force partially or completely compensates the spring force. This ensures that the sensor mass at or near the neutral point is not affected by any (or almost not affected by) the effective spring force, even if the sensor parameters change over time or due to environmental influences.

[0032] Adjusting the sensor mass about the neutral point may be to make the offset of the sensor mass close to the neutral point or to adjust the offset of the sensor mass to the neutral point. As mentioned above, this improves the zero bias stability.

[0033] A method for adjusting the offset of a sensor mass block of the above-mentioned acceleration sensor may include: determining a relationship between a first electrostatic force and the offset of the sensor mass block for at least two different fine-tuning voltages; determining a neutral point of the offset as follows based on the relationship between the first electrostatic force and the offset of the sensor mass block: at this offset, the corresponding first electrostatic forces are the same for different fine-tuning voltages; and adjusting the offset of the sensor mass block about the neutral point. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention is described below by way of example with reference to the accompanying drawings. However, the present invention should not be limited to the following embodiments, but is only determined by the content of the claims. In the accompanying drawings:

[0035] Figure 1 shows a schematic diagram of an acceleration sensor;

[0036] Figure 2 A schematic diagram showing the dependence of the force measured by an acceleration sensor on the deflection of a sensor mass of the acceleration sensor at different fine-tuning voltages;

[0037] Figure 3 shows a schematic diagram of another acceleration sensor; and,

[0038] Figure 4 A schematic flow chart of a method for adjusting the deflection of a sensor mass of an acceleration sensor to a position with a stable zero bias is shown. DETAILED DESCRIPTION

[0039] Figure 1 A schematic diagram of an acceleration sensor 100 is shown.

[0040] The acceleration sensor 100 has a substrate 110. A sensor mass 120 is mounted above the substrate 110 via a spring element 130 so as to be movable along a movement axis x. The spring element 130 is fixedly connected to the substrate 110 with a first side of the spring element 130 and is fixedly connected to the sensor mass 120 with a second side of the spring element 130. The spring element 130 allows the sensor mass 120 to be deflected along the movement axis x. For example, the spring element 130 can be designed as a bending beam spring, which extends perpendicularly to the movement axis x and thus only allows movement along the movement axis x, while movement perpendicular to the movement axis x is not possible. However, the spring element 130 can also have any other shape that causes the sensor mass 120 to be deflected along the movement axis x.

[0041] The first fine tuning electrode 140 is connected to the sensor mass 120. Here, the first fine tuning electrode 140 is fixedly connected to the sensor mass 120. For example, the sensor mass 120 and the first fine tuning electrode 140 may be integrally formed, that is, the first fine tuning electrode 140 is a component of the sensor mass 120.

[0042] The second fine tuning electrode 150 is connected to the substrate 110 and corresponds to the first fine tuning electrode 140. Here, the second fine tuning electrode 150 is fixedly connected to the substrate 110. For example, the second fine tuning electrode 150 may be a component of the substrate 110.

[0043] The electrode pair of first fine tuning electrode 140 and second fine tuning electrode 150 is designed so that at a specific position of sensor mass 120, the force generated by first fine tuning electrode 140 and second fine tuning electrode 150 does not act on sensor mass 120. However, when deviated from this position, an electrostatic force Ft is generated, which acts on sensor mass 120 through fine tuning electrodes 140, 150.

[0044] Here, the first fine tuning electrodes 140 and the second fine tuning electrodes 150 do not have to be symmetrically mounted on the sensor mass 120 or the substrate 110. For example, all the first fine tuning electrodes 140 may be located on one side of the sensor mass 120 or at one end of the sensor mass 120.

[0045] When the sensor mass 120 is deflected along the motion axis x, the spring element 130 generates a spring force Ff, which moves the sensor mass 120 back to the initial position, in which the forces generated by the various spring elements 130 compensate each other or these forces disappear (mechanical zero point). At the same time, by applying a fine tuning voltage between the first fine tuning electrode 140 and the second fine tuning electrode 150, an electrostatic force Ft can be generated on the sensor mass 120, which is added to the spring force Ff to form an effective spring force.

[0046] It is thus possible to freely adjust the spring hardness or stiffness of the acceleration sensor 100 by means of the fine tuning voltage applied between the first fine tuning electrode 140 and the second fine tuning electrode 150. This makes it possible, for example, for the spring force Ff and the electrostatic force Ft to completely compensate each other, so that no restoring force is present in the event of a deflection of the sensor mass 120. However, the electrostatic force Ft can also overcompensate, i.e. exceed, the spring force Ff, so that in the event of only a small deflection of the sensor mass 120, the electrostatic force Ft reinforces the sensor mass 120 to a large deflection. Since this would lead to an immediate overloading of the sensor mass 120, in this way the acceleration sensor 100 should only be operated in a closed control loop with additional reset electronics.

[0047] The acceleration sensor 100 further has a sensor electrode 160 for reading out the acceleration, which is connected to the sensor mass 120 and corresponds to a schematically shown detection electrode 170, which is connected to the substrate 110. The voltage between the sensor electrode 160 and the detection electrode 170 generates an electrostatic force Fd on the sensor mass 120, which can be used to deflect the sensor mass 120. For a fixed voltage between the sensor electrode 160 and the detection electrode 170, the charge or the capacitance that can be derived therefrom depends on the deflection of the sensor mass 120 along the axis of motion x. This makes it possible to determine the deflection of the sensor mass 120 via the sensor electrode 160 and the detection electrode 170.

[0048] If the sensor mass 120 is to be at rest, the various forces acting on it must be balanced, i.e., Fd+Ft+Ff = 0. If the first electrostatic force Fd is understood as the force measured by the acceleration sensor 100, and the combination of the spring force Ff and the second electrostatic force Ft is understood as the effective spring force, then for small deflections, there is a linear relationship between the first electrostatic force and the deflection, the slope of which depends on the applied fine-tuning voltage.

[0049] This is Figure 2 , which depicts a graph of the first electrostatic force or effectively measured force Fd versus the displacement along the motion axis x for different fine tuning voltages. Each straight line represents the force-displacement characteristics of the system at a specific fine tuning voltage. These characteristics can be determined for a specific fine tuning voltage by adjusting various forces applied by the detection electrode 170 on the sensor electrode 160 and then reading the resulting displacement.

[0050] If at least two measurements are made for different trimming voltages, the intersection point N of all the straight lines is obtained in the diagram, at which point the first electrostatic force Fd causes the same offset "n" for all trimming voltages. This offset is called the "neutral point".

[0051] By changing the trimming voltage accordingly and the voltage between the sensor electrode 160 and the detection electrode 170, the neutral point of the offset can be determined in the acceleration sensor 100 and is sought to be the starting point for the acceleration measurement. At this point, the change in the trimming voltage has no effect on the forces acting on the sensor mass 120. Therefore, the zero bias affecting the acceleration measurement is stable with respect to such changes, thereby improving the reliability of the sensor in long-term operation. If the sensor mass 120 is brought to a starting position close to or corresponding to the neutral point, the zero bias stability can be improved.

[0052] Furthermore, after the initial position of the sensor mass has approached or occupied the neutral point, the fine-tuning voltage can be changed so that the second electrostatic force Ft partially or even completely compensates the spring force Ff. Figure 2 Indicated by arrow A in the figure. The fine-tuning voltage is varied until there is (almost) no slope in the force-displacement diagram, i.e. the horizontal line H is reached. With this configuration, the zero bias is stable even in the face of small displacements from the neutral point, since the forces acting on the sensor mass 120 do not change. This also improves the long-term stability and can also facilitate the operation of the acceleration sensor 100 under vibrations.

[0053] Here, the offset adjustment about the neutral point and the adjustment of the fine-tuning voltage for fully or partially compensating the spring force Ff can be achieved by automatically controlling the voltage applied to the fine-tuning electrodes 140, 150, the sensor electrode 160 and the detection electrode 170. In this way, the acceleration sensor 100 can be kept at the neutral point and the zero bias can be further stabilized. In addition, the controller can provide data about the change of the neutral point position over time, which can illustrate the high performance of the acceleration sensor 100.

[0054] It goes without saying that, depending on the specific configuration of the fine-tuning electrodes 140, 150, the sensor electrode 160 and the detection electrode 170, the first electrostatic force Fd, the second electrostatic force Ft and the displacement of the sensor mass 120 can be generated and read out in different ways. Figure 3 The acceleration sensor 100 schematically shown in FIG. 1 is used to exemplarily discuss a specific embodiment.

[0055] exist Figure 3 In the acceleration sensor 100 of FIG. 1 , the first fine-tuning electrode 140 is designed as an electrode plate, each of which is surrounded by two second fine-tuning electrodes 150 and forms a plate capacitor together with the two second fine-tuning electrodes 150. Here, the second electrostatic force is the resultant force of the two outer second fine-tuning electrodes 150 acting on the middle first fine-tuning electrode 140. Therefore, this force has no effect on the center positioning of the first fine-tuning electrode 140.

[0056] The sensor electrodes 160 and the detection electrodes 170 are designed as comb-shaped electrodes having electrode fingers meshing with each other. The sensor electrodes 160 and the detection electrodes 170 are divided into two groups of electrode pairs along the movement axis x. Figure 3 In FIG. 1 , the electrodes arranged at the left end of the sensor mass represent a first electrode pair, while the electrodes arranged at the right end represent a second electrode pair.

[0057] Now, if a given voltage is applied to only one of the two electrode pairs, the generated force originates only from the electrodes of this electrode pair. If the electrode pairs to which the voltage is applied are alternately changed, the generated first electrostatic force depends on which electrode pair is the one to which the voltage is applied for how long. Here, it is recommended to make a fast change in order to suppress inertia effects or hysteresis effects as much as possible. Therefore, the duty cycle of the voltage change from one electrode pair to the other electrode pair determines whether and in which direction the first electrostatic force is generated in the average value over time.

[0058] exist Figure 3 In an embodiment, the electrode pairs of the sensor electrode 160 and the detection electrode 170 are structurally identical. Therefore, applying a specified voltage only to the electrode pair on the left side will result in a force opposite to the case where the specified voltage is applied only to the electrode pair on the right side. If the voltage is applied to the left and right sides the same number of times within the reference period, that is, the duty cycle is set to 50 / 50, no force is generated in the time average value. By changing the duty cycle, the first electrostatic force acting on the sensor mass 120 in the time average value can be adjusted. Of course, the actual force here depends on the specific structure of the sensor and can be calculated. The duty cycle that can be specified externally allows the first electrostatic force to be specified externally.

[0059] At the same time, the capacitance of the capacitor formed by the electrode can be determined in a known manner from the charge passing through the electrode when a specified voltage is applied, for example by measuring the charge flow through the mass and the amplifier capacitor. Figure 3 The values ​​are derived for the electrode pairs of the left group in the same way as for the electrode pairs of the right group. Since the capacitance depends on the distance between the individual electrodes, this capacitance is a measure for the deflection of the sensor mass 120. The difference in capacitance between the left and right electrode pairs can be read. From this, the deflection of the sensor mass 120 can be determined.

[0060] In this way, the necessary measured values ​​can be determined in order to derive a force-displacement diagram for each applied fine-tuning voltage and to derive the neutral point therefrom.

[0061] Alternatively, it is also possible to dispense with the derivation of the first electrostatic force from the duty cycle and the derivation of the offset from the capacitance difference and use these variables directly for regulating the neutral point.

[0062] To this end, a different duty cycle is applied to each fine-tuning voltage and the corresponding capacitance difference is measured for each duty cycle. The resulting duty cycle-capacitance difference graph intersects at a point at which the duty cycle of each fine-tuning voltage leads to the same capacitance difference. Adjustment of this capacitance difference is equivalent to adjusting the offset with respect to the neutral point. In this way, the neutral point can be determined by a parameter that can be directly adjusted or read out, and the offset of the sensor mass (120) can be brought close to the neutral point or preferably adjusted to the neutral point. In particular, adjustment can be made according to the capacitance difference.

[0063] In this way, the neutral point can be reached and maintained in a simple manner.

[0064] Figure 4 A schematic flow chart of a method for adjusting a neutral point is shown, which method can be performed with an acceleration sensor configured in an equivalent manner to the above-described sensor.

[0065] In S100, a relationship between a first electrostatic force Fd and a deflection of a sensor mass (120) is determined for at least two different fine tuning voltages. In particular, a linear force-displacement curve may be determined for two or more fine tuning voltages.

[0066] In S110, a neutral point of the offset is determined according to the relationship between the first electrostatic force Fd and the offset of the sensor mass (120): at the offset, the corresponding first electrostatic force Fd is the same for different fine-tuning voltages. In particular, the neutral point can be determined according to the intersection of the determined force-displacement curve.

[0067] In S120, the offset of the sensor mass is adjusted with respect to the neutral point. In particular, the offset is adjusted to be close to the neutral point or preferably to the neutral point. This enables the acceleration sensor to operate at an operating point with improved long-term stability of the zero bias.

Claims

1. An acceleration sensor (100), comprising: a sensor mass (120) which is arranged above the substrate (110) by means of a spring element (130) and is movable along a movement axis (x); A first fine-tuning electrode (140), the first fine-tuning electrode being connected to the sensor mass block (120); A sensor electrode (160), the sensor electrode being connected to the sensor mass block (120); a second fine-tuning electrode (150), the second fine-tuning electrode being connected to the substrate (110) and corresponding to the first fine-tuning electrode (140); a detection electrode (170), the detection electrode being connected to the substrate (110) and corresponding to the sensor electrode (160), wherein: The sensor electrode (160) and the detection electrode (170) are designed to cause the sensor mass (120) to deflect along the motion axis (x) by applying a voltage, and to measure the deflection and a first electrostatic force (Fd) applied by the sensor electrode (160) and the detection electrode (170) on the sensor mass (120) to determine a relationship between the first electrostatic force (Fd) and the deflection of the sensor mass (120); The spring element (130) is designed to generate a spring force (Ff) on the sensor mass (120) when the sensor mass (120) is deflected along the movement axis (x); The acceleration sensor (100) is designed to generate a second electrostatic force (Ft) on the sensor mass block (120) by applying a fine-tuning voltage between the first fine-tuning electrode (140) and the second fine-tuning electrode (150), wherein the second electrostatic force is added to the spring force (Ff) to form an effective spring force; The sensor electrode (160) and the detection electrode (170) are designed to determine the relationship between the first electrostatic force and the offset of the sensor mass (120) for at least two different fine-tuning voltages, and to determine a neutral point therefrom for an offset where, when the offset occurs, the corresponding first electrostatic force is the same for the different fine-tuning voltages; and The acceleration sensor (100) is designed to adjust the voltage applied to the first fine-tuning electrode (140), the second fine-tuning electrode (150), the sensor electrode (160) and / or the detection electrode (170), so that the offset of the sensor mass block is adjusted by the sensor electrode (160) and the detection electrode (170) about the neutral point. in, The sensor electrodes (160) and the detection electrodes (170) are divided into a first pair of sensor electrodes (160) and detection electrodes (170) and a second pair of sensor electrodes (160) and detection electrodes (170); The first pair and the second pair are arranged at different positions along the motion axis (x); Applying a specified voltage alternately at a duty cycle to the first pair of sensor electrodes (160) and detection electrodes (170) and the second pair of sensor electrodes (160) and detection electrodes (170); The first electrostatic force can be changed by changing the duty cycle; determining a capacitance of a capacitor formed by the sensor electrode (160) and the detection electrode (170) when the specified voltage is applied to the corresponding sensor electrode (160) and the detection electrode (170); determining a deflection of the sensor mass (120) by a capacitance difference between the first pair of sensor electrodes (160) and detection electrodes (170) and the second pair of sensor electrodes (160) and detection electrodes (170); and, The relationship between the first electrostatic force and the offset is determined by the relationship between the applied duty cycle and the capacitance difference.

2. The acceleration sensor (100) according to claim 1, in, After adjusting the offset about the neutral point, the trimming voltage is adjusted such that the second electrostatic force partially or completely compensates the spring force.

3. The acceleration sensor (100) according to claim 1 or 2, in, varying the duty cycle for each of the trimming voltages and determining the capacitance difference for each duty cycle; and, In order to adjust the offset with respect to the neutral point, the duty cycle is adjusted in such a way that the same capacitance difference results for each of the different fine-tuning voltages.

4. The acceleration sensor (100) according to claim 1 or 2, in, The voltage applied to the first fine-tuning electrode (140), the second fine-tuning electrode (150), the sensor electrode (160) and / or the detection electrode (170) is automatically adjusted by a control circuit, thereby controlling the offset with respect to the neutral point.

5. The acceleration sensor (100) according to claim 1 or 2, in, The voltage applied to the first fine-tuning electrode (140) and the second fine-tuning electrode (150) is automatically adjusted by a control circuit so that the second electrostatic force partially or completely compensates for the spring force.

6. The acceleration sensor (100) according to claim 1 or 2, in, Adjusting the sensor mass (120) with respect to the neutral point is to make the offset of the sensor mass (120) close to the neutral point or to adjust the offset of the sensor mass (120) to the neutral point.

7. A method for adjusting the deflection of a sensor mass (120) of an acceleration sensor (100) according to any one of claims 1 to 6, the method include: Applying voltage to the first fine-tuning electrode (140), the second fine-tuning electrode (150), the sensor electrode (160) and / or the detection electrode (170) of the acceleration sensor (100); determining a relationship between a first electrostatic force (Fd) and a deflection of the sensor mass (120) for at least two different fine tuning voltages; determining a neutral point for a displacement (n) at which the first electrostatic force is the same for the different fine-tuning voltages according to a relationship between the first electrostatic force (Fd) and the displacement (n) of the sensor mass (120); and The voltage applied to the first fine-tuning electrode (140), the second fine-tuning electrode (150), the sensor electrode (160) and / or the detection electrode (170) is adjusted to adjust the offset of the sensor mass (120) about the neutral point.

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