Microsensor, method for measurement, and method for sensor state monitoring

Abstract

The invention relates to a microsensor (10) for measuring a physical measurement variable (14), comprising: a first measurement element (16) which can measure the measurement variable (14) in a first measurement region (54) with a first measurement characteristic (C1) and in a second measurement region (56) with a second measurement characteristic (C2), said second measurement region supplanting the first measurement region (54) by mechanical delimitation and being offset therefrom, and the first measurement element having a micromechanical first deflection element (18) which can be deflected according to the measurement variable (14); a second measurement element (28) which can measure the measurement variable (14) in a third measurement region (52) with a third measurement characteristic (C3), wherein the third measurement region (52) overlaps a transition (53) between the first and second measurement regions (54, 56) and forms a first overlap region (58) with the first measurement region (54) and a second overlap region (60) with the second measurement region (56), and wherein the measurement variable (14), which is present at least at the transition (53), can be measured by measurement of the second measurement element (28) on the basis of the third measurement characteristic (C3). The invention also relates to a method for measurement and to a method for sensor state monitoring.

Description

[0001] Description

[0002] title

[0003] Microsensor, measurement methods and sensor condition monitoring methods

[0004] The invention relates to a microsensor according to the preamble of claim 1. Furthermore, the invention relates to a method for measurement and a method for sensor condition monitoring.

[0005] State of the art

[0006] German patent DE 10 2021 207 736 A1 describes a pressure sensor element for pressure measurement in two measuring ranges, which closes an electrical contact between two contact elements when a certain pressure is applied. The electrical contact is effected by a mechanical stop of the contact elements. This mechanical stop reduces the effective diaphragm area on which the applied pressure acts to deflect the diaphragm. Due to the reduced diaphragm area, a change in pressure dependency must be taken into account above the first pressure value. This transition can be detected by sensor evaluation based on the resulting contact closure.

[0007] Disclosure of the invention

[0008] According to the present invention, a microsensor with the features of claim 1 is proposed. This allows the measurement of the measurand to be carried out more accurately and reliably. The microsensor can measure the measurand more accurately and reliably. The microsensor can be operated more efficiently. The measurement can be performed with a higher signal-to-noise ratio. The measurement range limits can be detected and taken into account more accurately. The microsensor can cover a wider measurement range of the measurand.

[0009] A measurement of one of the measuring elements in a measuring area outside the measuring element can be prevented by detecting the measuring range limits, thus making the measurement of the measured quantity less prone to error and more accurate.

[0010] The microsensor can be a capacitive and / or piezoresistive sensor. The microsensor can be a pressure sensor, a microphone, a flow sensor, and / or an accelerometer.

[0011] The microsensor can have an evaluation unit that operates the first and second measuring elements for measuring the measured quantity.

[0012] The measured quantity can be pressure, especially absolute pressure or pressure difference, sound, material flow, or acceleration. The measured quantity can be an environmental parameter of the microsensor. The pressure can be ambient pressure.

[0013] The mechanical limit can be a mechanical stop or the release of a previously existing mechanical stop. The mechanical stop can be effective with respect to the first deflection element. When the mechanical stop is in effect, the first deflection element can abut a limit, in particular a wall, a support, or a floor. The mechanical limit can be formed by a sacrificial layer. The mechanical limit can be implemented in or on the first deflection element, for example, by at least one thickening and / or stiffening.

[0014] The first measuring element can comprise a first measuring capacitance with at least one first measuring electrode coupled to the first deflection element and a rigid first counter electrode. The first measuring capacitance can be variable depending on the measured quantity, in particular depending on the deflection of the first deflection element. The first deflection element can be a diaphragm and / or a spring-loaded mass.

[0015] The second measuring element can be operated in at least a fourth measuring range with a fourth measuring characteristic for measuring the measured quantity. The third measuring range can be replaced by the fourth measuring range by mechanical limitation as the measured quantity increases. The fourth measuring range can directly follow the third measuring range. A characteristic curve of the second measuring element, specifying the third and fourth measuring characteristics, can exhibit a kink at the transition between the third and fourth measuring ranges. The characteristic curve of the second measuring element can exhibit several kinks in total.

[0016] The first measuring element can be operated in at least a fifth measuring range with a fifth measuring characteristic for measuring the measured quantity. The second measuring range can be replaced by the fifth measuring range by mechanical limitation as the measured quantity increases.

[0017] The first and second measuring elements can be electrically connected in a measuring bridge circuit. The first and / or second measuring element can be composed of individual measuring components. The measuring components can be connected in a measuring bridge circuit. The measuring bridge circuit can be a half-bridge or full-bridge circuit. The first and second measuring elements can be arranged next to each other with respect to the environment of the microsensor containing the measured quantity. The first and second measuring elements can face the environment of the microsensor.

[0018] The microsensor can have at least one additional measuring element that can be operated in at least one further measuring range of the measured quantity. This additional measuring element can have several further measuring ranges offset from one another.

[0019] The measurement characteristic can be a measurement sensitivity or sensitivity with respect to the measured quantity. The measurement characteristic can indicate a relationship between an output quantity of the respective measuring element, for example an electrical voltage, and the measured quantity.

[0020] The second measuring range can connect directly to the first measuring range. Alternatively, the first measuring range can be separated from the second measuring range. In this case, a further measuring range of the first measuring element between the first and second measuring ranges may be omitted.

[0021] The third measuring range differs at least partially from the first and second measuring ranges.

[0022] The first overlap area can be the same size as, smaller than, or larger than the second overlap area.

[0023] The transition can be abrupt or occur over a range that may span multiple measured values ​​of the quantity. The exact position of the transition may be unknown and may be subject to part-specific variations.

[0024] A combined measurement characteristic of the microsensor with respect to the measurement of the measured quantity can be derived from the first, second, and third measurement characteristics. This allows for a more consistent and, on average, higher measurement accuracy. The combined measurement characteristic can be continuously, and in particular, continuously, differentiable. The combined measurement characteristic can be generated by combining and weighting the first and third measurement characteristics in the first overlap region, and / or by combining and weighting the second and third measurement characteristics in the second overlap region, and / or by combining and weighting the first, second, and third measurement characteristics at the transition point.

[0025] In a preferred embodiment of the invention, it is advantageous if the second measuring element comprises a deflectable micromechanical second deflection element that detects the measured quantity as a function of a deflection. The second deflection element can be a diaphragm and / or a spring-loaded mass. The first and second deflection elements can be spatially separated from each other. The first and second deflection elements can be joined together in one piece, in particular monolithically.

[0026] The second measuring element can have a second measuring capacitance with at least one second measuring electrode coupled to the second deflection element and a rigid second counter electrode. The second measuring capacitance can be variable depending on the measured quantity, in particular depending on the deflection of the second deflection element.

[0027] In a preferred embodiment of the invention, the third measuring range has a lower limit that is lower than the upper limit of the first measuring range. The lower limit of the third measuring range can lie outside the second measuring range and within the first measuring range. The upper limit of the first measuring range can lie within the third measuring range.

[0028] In a preferred embodiment of the invention, it is advantageous if the third measuring range has a lower measuring range limit that is greater than the lower measuring range limit of the first measuring range. The first overlap range can comprise at least 5%, preferably 15%, and particularly preferably 50% of the first measuring range. The first overlap range can comprise at most 75%, preferably 65%, and particularly preferably at most 50% of the first measuring range.

[0029] In a particular embodiment of the invention, it is advantageous if the third measuring range has an upper measuring range limit that is greater than a lower measuring range limit of the second measuring range. The upper measuring range limit of the third measuring range can lie outside the first measuring range and within the second measuring range. The lower measuring range limit of the second measuring range can lie within the third measuring range.

[0030] In a preferred embodiment of the invention, it is advantageous if the third measuring range has an upper measuring range limit that is smaller than the upper measuring range limit of the second measuring range. The second overlap range can comprise at least 5%, preferably 15%, and particularly preferably 50% of the second measuring range. The second overlap range can comprise at most 75%, preferably 65%, and particularly preferably at most 50% of the second measuring range.

[0031] In a preferred embodiment of the invention, a characteristic curve of the first measuring element, which defines the first and second measuring characteristics, has a kink at the transition between the first and second measuring ranges. The characteristic curve of the first measuring element can have several kinks in total.

[0032] According to the present invention, a measurement method with the features of claim 8 is further proposed. The detection of the transition can be performed before and / or after the initial commissioning of the microsensor. The detection of the transition can be performed during application-side operation of the microsensor, in particular once, on demand, or regularly. If the transition is a transition zone, the detection of the transition can include the detection of the beginning and / or the end of the transition zone.

[0033] In a preferred embodiment of the invention, the measurement of the measured quantity is carried out at least within the first overlap area on the basis of an overall measurement characteristic formed from the first and second measurement characteristics.

[0034] The first and second measuring elements can be operated alternately or simultaneously, at least temporarily or continuously, to measure the measured quantity, especially within the overlapping measuring ranges of the first and second measuring elements.

[0035] In a preferred embodiment of the invention, a measurement calibration of the first and / or second measuring element is performed during the measurement of the measured quantity, depending on the measured quantity. This calibration can be carried out as a trim process end-of-line, i.e., at the end of sensor manufacturing, or end-of-assembly, i.e., after the microsensor has been installed in the application. Typically, defined environmental conditions, such as temperature, pressure, and / or humidity, are set in a test chamber in which the microsensor or the application containing the microsensor is located. The set environmental conditions are determined or controlled via a reference sensor, whereby static or dynamic states can be adopted. Static means that the process waits until the desired conditions are reached.Dynamic means that the test chamber operates under more extreme conditions, and the trim process is performed during the transition to these conditions. Typically, the sensor behavior is described by a more complex relationship that may include a larger number of calibration parameters, particularly trim parameters. The temperature behavior can be described using multiple temperature measurement points, and the pressure behavior using multiple pressure measurement points combined with the temperature behavior. The calibration parameters, especially the trim parameters, can be derived from the measured quantity and, for example, used in a mathematical formula, which may include at least one additional constant.

[0036] For measured quantities smaller than the transition point, the measurement can be performed using the first measurement characteristic of the first measuring element, and before or upon reaching the transition point, the measurement can be switched to the third measurement characteristic of the second measuring element. For measured quantities larger than the transition point, the measurement can be switched from the third measurement characteristic back to the measurement using the second measurement characteristic of the first measuring element.

[0037] The switch from the first to the third measurement characteristic can be offset from the transition point for smaller measured quantities, while the transition point remains covered by the third measurement range. Similarly, the switch from the third to the second measurement characteristic can be offset from the transition point for larger measured quantities, while the transition point remains covered by the third measurement range. The switch from the first to the third measurement characteristic occurs within the first overlap range. The switch from the third to the second measurement characteristic occurs within the second overlap range.

[0038] Within the first overlap region, the measurand can be measured using either the first or the second measuring element. The measurements of the first and second measuring elements can be weighted against each other to obtain an overall measurement of the measurand. The weighting can be variable in the first overlap region, particularly shifting towards the second measuring element as the measurand increases, for example, stepwise or continuously, and especially with continuous differentiation. The weighting can also be variable in the second overlap region, particularly shifting towards the first measuring element as the measurand increases, for example, stepwise or continuously, and especially with continuous differentiation.

[0039] In a preferred embodiment of the invention, it is advantageous if the transition is detected by comparing the measurement of the first measuring element with the measurement of the second measuring element and / or by comparing the measurement of the first and / or second measuring element with a reference. This allows the transition to be reliably detected, and the second measuring element can optionally be used to measure the measurand as an alternative or additional measure. The reference can be stored in a retrievable location. The comparison of the measurement of the first and second measuring elements can be used to detect the transition during application-side operation of the microsensor. The comparison of the measurement of the first and / or second measuring element with the reference can also be used to detect the transition before initial commissioning of the microsensor.

[0040] The reference can be a reference measurement. The reference measurement can be obtained by another sensor. According to the present invention, a method for sensor condition monitoring with the features of claim 10 is further proposed. The detection of the sensor condition can be the detection of sensor impairment. The sensor impairment can be a deposit on a surface of the microsensor, an influence of temperature, an influence of humidity, damage, for example a leak, aging, and / or hysteresis of the microsensor.

[0041] The measurement procedure and / or the sensor condition monitoring procedure can be performed by the evaluation unit of the microsensor.

[0042] The reference can be a reference measurement. The reference measurement can be obtained from another sensor.

[0043] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations.

[0044] Character description

[0045] The invention is described in detail below with reference to the illustrations. These show, in detail:

[0046] Figure 1: A cross-section of a microsensor in a special embodiment of the invention.

[0047] Figure 2: A cross-section of the microsensor from Figure 1 in other states.

[0048] Figure 3: An arrangement of measuring ranges of a microsensor in a further special embodiment of the invention.

[0049] Figure 4: A measurement characteristic of a microsensor in a further special embodiment of the invention.

[0050] Figure 5: A measurement characteristic of a microsensor in a further specific embodiment of the invention. Figure 1 shows a cross-section of a microsensor in a specific embodiment of the invention. The microsensor 10 is arranged for measuring a physical quantity and is here, in particular, designed as a capacitive pressure sensor 12 for measuring ambient pressure as the quantity 14. In Figure 1 a), the microsensor 10 is shown in a state not affected by the quantity 14. The microsensor 10 comprises a first measuring element 16, which is configured to measure the ambient pressure in a first measuring range, in particular in a first pressure range, with a first measurement characteristic, and in a second measuring range, in particular a second pressure range, which is mechanically delimited from and offset by the first measuring range, with a second measurement characteristic.The first measuring element 16 comprises a micromechanical first deflection element 18 which can be deflected depending on the ambient pressure, for example a deflectable first membrane 20.

[0051] The first measuring element 16 comprises a first measuring capacity 22 with a first measuring electrode 24 which is deflectably coupled to the first deflection element 18 and a rigid first counter electrode 26 opposite this.

[0052] Furthermore, the microsensor 10 comprises a second measuring element 28 that measures the ambient pressure in a third measuring range, in particular a third pressure range, with a third measuring characteristic. The second measuring element 28 comprises a deflectable micromechanical second deflection element 30, which detects the ambient pressure as a function of a deflection and is, for example, a deflectable second diaphragm 32. The second deflection element 30 is arranged next to the first deflection element 18 with respect to an environment 34 of the microsensor 10.

[0053] The second measuring element 28 comprises a second measuring capacitance 36 with a second measuring electrode 40, which is deflected by a coupling element 38 arranged on the second deflection element 30 and is coupled to a rigid second counter electrode 42 opposite it. The coupling element 38 is initially spaced apart from the second measuring electrode 40. Figure 1b) shows the microsensor 10 in a state acted upon by the measured quantity 14, in which the first deflection element 18 is deflected and thus the first measuring capacitance 22 is changed. The second measuring electrode 40 is deflected by the coupling element 38. A lower measuring range limit of the third measuring range is thus exceeded, while an upper measuring range limit of the first measuring range has not yet been reached.This means that even if the second measuring electrode 40 is already deflected and thus the third measuring range is effective, the first measuring range of the first measuring element 16 can also be partially overlapping with the third measuring range.

[0054] Figure 2 a) shows the microsensor 10 in a state subjected to a measured quantity increased compared to Figure 1 b), in which the upper measuring range limit of the first measuring range is reached.

[0055] A stop element 44 on the first deflection element 18 provides a mechanical limit to the deflection of the first deflection element 18. The first measuring range of the first measuring element 16 is limited by the stops of the stop element 44 against a cavern floor 46 of the microsensor 10. The first deflection element 18 exhibits a modified deflection characteristic due to the stop element 44. This enables the measurement of a higher ambient pressure via the first measuring capacity 22 through the second measuring characteristic of the first measuring element 16.

[0056] The second measuring electrode 40 is deflected even further. The measured quantity 14 present at the transition between the first and second measuring ranges can be measured by measuring the second measuring element 28 using the third measuring characteristic. This allows the transition of the measuring range at the first measuring element 16 to be bridged or supplemented by the second measuring element 28 with respect to the measurement of the measured quantity 14.

[0057] In Figure 2 b), a lower measuring range limit of the second measuring range is exceeded and the first deflection element 18, which has the second measuring characteristic and the second measuring electrode 40 are deflected even further by a further increased measured quantity 14.

[0058] In Figure 2 c), a deflection of the second deflection element 30, and thus a deflection of the second measuring electrode 40, and thus in turn a change in the second measuring capacitance 36, is limited by a further stop element 48 on the second deflection element 30. An upper measuring range limit of the third measuring range is reached with stops of the further stop element 48 on a wall projection 50.

[0059] However, the upper limit of the second measuring range has not yet been reached, and the first deflection element 18 is still deflected further. The measurement of the measured quantity 14 is now carried out exclusively by the second measuring characteristic of the first measuring element 16.

[0060] Figure 3 shows an arrangement of measuring ranges of a microsensor in a further specific embodiment of the invention. The third measuring range 52 overlaps the transition 53 between the first measuring range 54 and the second measuring range 56 and forms a first overlap range 58 with the first measuring range 54 and a second overlap range 60 with the second measuring range 56. The lower measuring range limit L3 of the third measuring range 52 is greater than the lower measuring range limit L1 of the first measuring range 54 and less than the upper measuring range limit H1 of the first measuring range 54. Furthermore, the upper measuring range limit H3 of the third measuring range 52 is greater than the lower measuring range limit L2 of the second measuring range 56 and less than the upper measuring range limit H2 of the second measuring range 56.

[0061] In the second overlap area 60, the first measuring element 16 with the second measuring characteristic and the second measuring element 28 with the third measuring characteristic are effective.

[0062] Furthermore, a fourth measuring range 62 is provided, for example, of the second measuring element 28. The fourth measuring range 62 partially overlaps the second measuring range 56. Figure 4 shows a measuring characteristic of a microsensor in another specific embodiment of the invention. The measuring characteristic 64 can be a measuring sensitivity and can be described by a characteristic curve as the relationship between an output variable of the respective measuring element and the measured variable. The characteristic curve K1 of the first measuring element exhibits a kink 66 at the transition 53 between the first and second measuring ranges 54, 56. The characteristic curve K2 of the second measuring element has a fourth measuring range 62 adjacent to the third measuring range 52.

[0063] Furthermore, the characteristic curve K1 of the first measuring element has a fifth measuring range 68 adjacent to the second measuring range 56. Thus, the characteristic curve K1 of the first measuring element comprises a total of two kinks 66, and the characteristic curve K2 of the second measuring element comprises one kink 66. The third measuring range 52 spans the two kinks 66 of the first measuring element.

[0064] Figure 5 shows a measurement characteristic of a microsensor in a further specific embodiment of the invention. The first measurement characteristic C1 and the second measurement characteristic C2 of the first measuring element, as well as the third measurement characteristic C3 and the fourth measurement characteristic C4 of the second measuring element, can also be non-linear and preferably continuously differentiable, as shown here. When measuring the measurand, at least within overlapping measurement ranges between the first and second measuring elements, the measurements of the first and second measuring elements can be used to acquire the measurand. The measurements of the first and second measuring elements can be combined into a single overall measurement characteristic Ct by data fusion. This allows for a more uniform and, on average, higher measurement accuracy. The overall measurement characteristic Ct can be continuously, and in particular, continuously differentiable.

[0065] The measurement sensitivity, shown here as the slope in the characteristic curve, is greatest shortly before the upper measurement range limits H1 and H3 of the first and third measurement ranges 52 and 54. Conversely, the measurement sensitivity is lowest at the beginning of the second measurement range 56. By combining the measurement characteristics C1, C2, C3, and C4 of the first and second measuring elements, the overall measurement characteristic Ct can, for example, exhibit a comparatively steeper slope in the region of the lower slope of the second measurement range 56, thus corresponding to an increased measurement sensitivity of the measured quantity in this measurement range.

Claims

Patent claims 1. Microsensor (10) for measuring a physical quantity (14), comprising a first measuring element (16) with a first measuring characteristic (C1) and a second measuring element (56) with a second measuring characteristic (C2) that replaces and is offset from the first measuring area (54) by mechanical limitation, and a second measuring element (18) with a micromechanical first deflection element (18) that can be deflected depending on the quantity (14), and a second measuring element (28) that can be measured in a third measuring area (52) with a third measuring characteristic (C3), characterized in that the third measuring area (52) overlaps a transition (53) between the first and second measuring areas (54, 56) and forms a first overlap area (58) with the first measuring area (54) and a second overlap area (60) with the second measuring area (56),wherein the measured quantity (14) present at least at the transition (53) can be measured by measuring the second measuring element (28) using the third measuring characteristic (C3).

2. Microsensor (10) according to claim 1 , characterized in that the second measuring element (28) has a deflectable micromechanical second deflection element (30) which detects the measured quantity (14) depending on a deflection.

3. Microsensor (10) according to claim 1 or 2, characterized in that the third measuring range (52) has a lower measuring range limit (L3) which is smaller than an upper measuring range limit (H1) of the first measuring range (54).

4. Microsensor (10) according to one of the preceding claims, characterized in that the third measuring range (52) has a lower has a measuring range limit (L3) that is greater than a lower measuring range limit (L1) of the first measuring range (54).

5. Microsensor (10) according to one of the preceding claims, characterized in that the measured quantity (14) is measurable at least within the first overlap area (58) on the basis of an overall measurement characteristic (Ct) formed from the first and second measurement characteristics (C1 , C2).

6. Microsensor (10) according to one of the preceding claims, characterized in that a measurement adjustment of the first and / or second measuring element (16, 28) during the measurement of the measured quantity (14) is dependent on the measured quantity (14).

7. Microsensor (10) according to one of the preceding claims, characterized in that a characteristic curve of the first measuring element (16) indicating the first and second measuring characteristics (C1 , C2) has a kink (66) at the transition (53) between the first and second measuring range (54, 56).

8. Method for measuring a measurand (14), comprising the steps of providing a microsensor (10) according to any one of the preceding claims, Detecting the transition (53) between the first and second measuring range (54, 56) depending on a measurement with the second measuring element (28) with the third measuring characteristic (C3) in the third measuring range (52).

9. Method for measurement according to claim 6, characterized in that the transition (53) is detected depending on a comparison of the measurement of the first measuring element (16) and the measurement of the second measuring element (28) and / or a comparison of the measurement of the first and / or second measuring element (16, 28) and a reference.

10. Method for monitoring the sensor state of a microsensor (10) according to any one of claims 1 to 7, comprising the steps of performing a measurement of a measurand (14) by a measurement method according to any one of claims 8 or 9, detecting a sensor state of the microsensor (10) that influences the measurement of the measurand (14) depending on a comparison between the measurement of the measurand (14) of the first measuring element (16) and the measurement of the measurand (14) of the second measuring element (28) and / or a comparison of the measurement of the measurand (14) of the first and / or second measuring element (16, 28) and a reference.

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