Method and electronic circuit for testing a sensor

Abstract

The invention relates to a method for testing a sensor in an electronic circuit. The sensor comprises a first sensor element and a first reference element in a first branch of a Wheatstone bridge circuit and a second sensor element and a second reference element in a second branch parallel to the first branch. The Wheatstone bridge circuit has a first input for a first reference signal and a second input for a second reference signal, which inputs are connected to the branches, respectively. The reference signals are provided by means of a control logic unit. The first branch has a first signal output between the first sensor element and the first reference element. The second branch has a second signal output between the second sensor element and the second reference element. A first useful signal can be determined on the first signal output and a second useful signal on the second signal output. The first signal output is connected to a first amplifier input of an amplifier by means of a first switch and the second signal output is connected to a second amplifier input of the amplifier by means of a second switch. The method comprises the following steps: opening the first switch or the second switch; applying a predefined first and / or second reference signal; analyzing the first or second useful signal as to whether there is a damage of the sensor or a damage of the electrical connection between the sensor and the electronic circuit.

Description

Technical Field

[0001] This invention relates to a method for testing sensors and an electronic circuit. The method is particularly suitable for enabling self-testing of sensors and associated electronic circuits. Background Technology

[0002] A known capacitive sensor is characterized by two measuring capacitors and two reference capacitors being analyzed using a Wheatstone bridge circuit. This principle is disclosed, for example, in US 2010 / 0180 687A1. Here, the capacitors to be analyzed can be arranged within a micromechanical structure, such as a MEMS structure, and are particularly configured for measuring pressure, acceleration, and / or rotational speed. If the sensor and / or the electronic circuitry used for analysis malfunctions, for example, due to damage after a certain period of operation, the measurement results will be incorrect. However, for known sensors, this is not identifiable during sensor operation.

[0003] Fault identification in the Wheatstone bridge circuit of the sensor is known from documents JP 2015-021 790A and DE 10 2013 206 646 A1, respectively. Summary of the Invention

[0004] One object of the present invention is to provide a method for testing sensors, which can identify faults in the sensors or circuits. Furthermore, another object of the present invention is to provide a corresponding circuit.

[0005] These tasks are addressed using the subject matter of the independent patent claims. Advantageous extensions are described in the dependent patent claims.

[0006] The method according to the invention is used to test a sensor within an electronic circuit. The sensor includes a first sensor element and a first reference element in a first branch of a Wheatstone bridge circuit, and a second sensor element and a second reference element in a second branch of the same circuit, wherein the first and second branches are connected in parallel. The Wheatstone bridge circuit has a first input terminal for a first reference signal and a second input terminal for a second reference signal, wherein the first and second input terminals are respectively connected to the first and second branches. The first and second reference signals are provided by means of a control logic unit, which is part of the electronic circuit. The first branch has a first signal output terminal between the first sensor element and the first reference element. The second branch has a second signal output terminal between the second sensor element and the second reference element. A first useful signal can be determined at the first signal output terminal, and a second useful signal can be determined at the second signal output terminal. The first signal output terminal is connected to a first amplifier input terminal of an amplifier via a first switch. The amplifier can be configured as a low-noise charge-to-voltage converter. Low-noise charge-to-voltage converters are particularly amplifiers. The second signal output terminal is connected to the second amplifier input terminal of the amplifier via a second switch. The amplifier is part of the electronic circuit.

[0007] To identify the fault, the first switch is closed and the second switch is opened. Then, a positive reference signal is applied to the first input terminal and a negative reference signal is applied to the second input terminal, and the first useful signal is recorded. Then, the first switch is opened and the second switch is closed. Then, a positive reference signal is applied to the first input terminal and a negative reference signal is applied to the second input terminal, and the second useful signal is recorded. If the first useful signal and the second useful signal have different absolute values, especially if the difference between the first useful signal and the second useful signal exceeds a predetermined tolerance, then the sensor is damaged.

[0008] In particular, it can be configured to analyze and process the second useful signal when the first switch is open, and analyze and process the first useful signal when the second switch is open.

[0009] It can be configured that the first and second sensor elements include variable capacitance, such as the variable capacitance of a micromechanical structure, while the first and second reference elements have immutable capacitance. Specifically, it can be configured that the parameter to be measured (e.g., pressure, acceleration, or rotational rate) acts on the micromechanical structure, causing it to deviate. The capacitance integrated within the micromechanical structure changes here and represents the first and second sensor elements.

[0010] A first reference element is disposed between the second input terminal and the first signal output terminal. A second reference element is disposed between the first input terminal and the second signal output terminal. A second sensor element is disposed between the second input terminal and the second signal output terminal.

[0011] In one implementation, the first switch is disconnected and the second switch is closed, then the second input terminal is grounded, and a positive reference signal is applied to the first input terminal. The second useful signal then contains information about the second reference element, wherein the information about the second reference element is analyzed in relation to any damage to the electrical connection between the sensor and the electronic circuitry.

[0012] In one embodiment, the first switch is then closed and the second switch is opened. Furthermore, the first input terminal is then grounded, and a positive reference signal is applied to the second input terminal. The first useful signal then contains information about the first reference element, wherein the information about the first reference element is analyzed in relation to any damage to the electrical connection between the sensor and the electronic circuitry.

[0013] In one embodiment, the first useful signal is analyzed in terms of its absolute value. In another embodiment, the second useful signal is analyzed in terms of its absolute value.

[0014] The present invention also includes a computer program comprising instructions that, when executed by a computer, cause the computer to perform one of the methods according to the present invention.

[0015] The present invention also includes a machine-readable storage medium on which a computer program according to the present invention is stored.

[0016] The present invention also includes an electronic circuit having a control logic unit, a sensor, and an amplifier. The sensor has a first sensor element and a first reference element in a first branch of a Wheatstone bridge circuit, and a second sensor element and a second reference element in a second branch of the Wheatstone bridge circuit. The first branch and the second branch are connected in parallel. The Wheatstone bridge circuit has a first input terminal for a first reference signal and a second input terminal for a second reference signal, wherein the first input terminal and the second input terminal are respectively connected to the first branch and the second branch. The first reference signal and the second reference signal are provided by means of the control logic unit. The first branch has a first signal output terminal between the first sensor element and the first reference element, and the second branch has a second signal output terminal between the second sensor element and the second reference element. A first useful signal can be determined at the first signal output terminal and a second useful signal can be determined at the second signal output terminal, wherein the first signal output terminal is connected to a first amplifier input terminal of the amplifier via a first switch, and the second signal output terminal is connected to a second amplifier input terminal of the amplifier via a second switch. The electronic circuit is configured to apply the first reference signal to the first input terminal and the second reference signal to the second input terminal by means of the control logic unit, open and close the first switch and the second switch, analyze and process the first useful signal and / or the second useful signal, and perform the method according to the invention. Attached Figure Description

[0017] Embodiments of the present invention are illustrated with reference to the following figures. The figures show:

[0018] Figure 1 An electronic circuit;

[0019] Figure 2 First flowchart;

[0020] Figure 3 Second flowchart; and

[0021] Figure 4 Third flowchart. Detailed Implementation

[0022] Figure 1An electronic circuit 1 is shown, comprising a control logic unit 2, a sensor 3, and an amplifier 5. The sensor 3 has a first sensor element 31 and a first reference element 33 in a first branch 41 of a Wheatstone bridge circuit 4, and a second sensor element 32 and a second reference element 34 in a second branch 42 of the Wheatstone bridge circuit 4. The first branch 41 and the second branch 42 are connected in parallel. The Wheatstone bridge circuit 4 has a first input terminal 43 for a first reference signal and a second input terminal 44 for a second reference signal, wherein the first input terminal 43 and the second input terminal 44 are connected to the first branch 41 and the second branch 42, respectively. The first reference signal and the second reference signal are provided by means of the control logic unit 2. For this purpose, the control logic unit 2 is connected to the first input terminal 43 and the second input terminal 44. The first branch 41 has a first signal output terminal 45 between the first sensor element 31 and the first reference element 33. The second branch 42 has a second signal output terminal 46 between the second sensor element 32 and the second reference element 34. A first useful signal can be determined at the first signal output terminal 45, and a second useful signal can be determined at the second signal output terminal 46. The first signal output terminal 45 is connected to the first amplifier input terminal 53 of the amplifier 5 via a first switch 51. The second signal output terminal 46 is connected to the second amplifier input terminal 54 of the amplifier 5 via a second switch 52. The electronic circuit 1 is configured to apply a first reference signal to the first input terminal 43 and a second reference signal to the second input terminal 44 by means of the control logic unit 2, open and close the first switch 51 and the second switch 52, and analyze and process the first useful signal and / or the second useful signal.

[0023] It can be configured that the first sensor element 31 and the second sensor element 32 include variable capacitance, such as the variable capacitance of a micromechanical structure, and that the first reference element 33 and the second reference element 34 have immutable capacitance. In particular, it can be configured that the parameter to be measured (e.g., pressure, acceleration, or rotational rate) acts on the micromechanical structure, causing it to deviate. The capacitance integrated in the micromechanical structure changes here, and represents the first sensor element 31 and the second sensor element 32.

[0024] In one embodiment, such as Figure 1 As shown, the first sensor element 31 is arranged between the first input terminal 43 and the first signal output terminal 45, the first reference element 33 is arranged between the second input terminal 44 and the first signal output terminal 45, the second reference element 34 is arranged between the first input terminal 43 and the second signal output terminal 46, and the second sensor element 32 is arranged between the second input terminal 44 and the second signal output terminal 46.

[0025] Also in Figure 1The diagram shows an optional analog-to-digital converter (ADC) 6 and an optional digital signal processor (DSP) 7. The ADC converts analog signals into digital signals, and the DSP further processes the digital signals. Both the ADC 6 and DSP 7 are part of the electronic circuit 1. Additionally, an optional control device 8 is shown, which can operate the control logic unit 2 and analyze and process useful signals.

[0026] Figure 2 A first flowchart 100 of a method is shown, which can be, for example, by means of... Figure 1 The method is implemented by the control device 8 of the electronic circuit 1. The method includes the following steps:

[0027] - In the first method step 101, disconnect the first switch 51 or the second switch 52;

[0028] - In step 102 of the second method, a pre-given first reference signal and / or a pre-given second reference signal are applied;

[0029] - In the third method step 103, the first useful signal or the second useful signal is analyzed and processed as follows: whether there is damage to the sensor 3 or damage to the electrical connection between the sensor 3 and the electronic circuit 1.

[0030] In one embodiment, in the first method step 101, the first switch 51 is disconnected and the second switch 52 is closed. Then, in the second method step 102, the second input terminal 44 is grounded, and a positive reference signal is applied to the first input terminal 43. Here, the positive reference signal can be a square wave signal. Then, the second useful signal contains information about the second reference element 34. In the third method step 103, the information about the second reference element 34 is analyzed in relation to potential damage to the electrical connection between the sensor 3 and the electronic circuit 1.

[0031] The analysis can be performed, in particular, in such a way that a predetermined value within a predetermined measurement tolerance is compared with a measured value for the second reference element 34, for example, comparing the nominal capacitance of the second reference element 34 with the capacitance measured as a second useful signal.

[0032] In one implementation, the first useful signal is analyzed in terms of its absolute value.

[0033] Figure 3 A second flowchart 100 of a method is shown, which can be, for example, by means of Figure 1 The method is implemented by the control device 8 of the electronic circuit 1. This method includes the steps described in the preceding three paragraphs. Figure 2The method steps are as follows. Furthermore, in the fourth method step, the first switch 51 is closed and the second switch 52 is opened. Subsequently, in the fifth method step 105, the first input terminal 43 is grounded, and a positive reference signal is applied to the second input terminal 44. Here, the positive reference signal can be a square wave signal. Then, the first useful signal contains information about the first reference element 33. In the sixth method step 106, the information about the first reference element 33 is analyzed in terms of potential damage to the electrical connection between the sensor 3 and the electronic circuit 1.

[0034] The analysis can be performed, in particular, in such a manner that a predetermined value within a predetermined measurement tolerance is compared with a measured value for the first reference element 33, for example, comparing the nominal capacitance of the first reference element 33 with the capacitance measured as a first useful signal. Here, the predetermined tolerance can be taken into account.

[0035] In one implementation, the second useful signal is analyzed in terms of its absolute value. It can be configured that not only the first useful signal but also the second useful signal is analyzed in terms of its absolute value. For example, if the absolute values ​​of the useful signals differ, then a failure in the connection between sensor 3 and the electronic circuitry can be assumed, wherein these differences can be configured to be outside a predetermined measurement tolerance.

[0036] Figure 4 A third flowchart 100 of a method is shown, which can be, for example, by means of... Figure 1 The electronic circuit 1 is controlled by the control device 8. The third flowchart can be implemented based on the combination of... Figure 2 and Figure 3The described method can be implemented, or it can be implemented alone. In the seventh method step 107, the first switch 51 is closed and the second switch 52 is opened. Subsequently, in the eighth method step 108, a positive reference signal is applied to the first input terminal 43 and a negative reference signal is applied to the second input terminal 44. Here, the positive reference signal can be a square wave signal. Here, the negative reference signal can also be a square wave signal. In addition, in the eighth method step 108, the first useful signal is recorded. In the subsequent ninth method step 109, the first switch 51 is opened and the second switch 52 is closed. In the subsequent tenth method step 110, a positive reference signal is applied to the first input terminal 43 and a negative reference signal is applied to the second input terminal 44. Here, the positive reference signal can be a square wave signal. Here, the negative reference signal can also be a square wave signal. In addition, in the tenth method step 110, the second useful signal is recorded. In the eleventh method step 111, it is checked whether there is any damage to the sensor 2. This is the case when the first useful signal and the second useful signal have different absolute values. Here, a pre-defined tolerance can be taken into account.

[0037] A computer program includes instructions that, when executed by a computer, cause the computer to perform the method. The computer program can be stored in a machine-readable storage medium. In particular, the computer program can be stored in a control device 8.

[0038] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and different variations thereof can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A method for testing a sensor (3) within an electronic circuit (1), wherein, The sensor (3) includes a first sensor element (31) and a first reference element (33) in a first branch (41) of a Wheatstone bridge circuit (4), and a second sensor element (32) and a second reference element (34) in a second branch (42) of the Wheatstone bridge circuit (4), wherein the first branch (41) and the second branch (42) are connected in parallel, wherein the Wheatstone bridge circuit (4) has a first input terminal (43) for a first reference signal and a second input terminal (44) for a second reference signal, wherein the first input terminal (43) and the second input terminal (44) are respectively connected to the first branch (41) and the second branch (42), wherein the first reference signal and the second reference signal are provided by means of a control logic unit (2), wherein the control logic unit (2) is part of the electronic circuit (1). The method comprises the following steps: First branch (41) has a first signal output terminal (45) between the first sensor element (31) and the first reference element (33), and second branch (42) has a second signal output terminal (46) between the second sensor element (32) and the second reference element (34). A first useful signal can be determined at the first signal output terminal (45), and a second useful signal can be determined at the second signal output terminal (46). The first signal output terminal (45) is connected to the first amplifier input terminal (53) of the amplifier (5) via a first switch (51). The second signal output terminal (46) is connected to the second amplifier input terminal (54) of the amplifier (5) via a second switch (52). The amplifier (5) is part of the electronic circuit (1). - Disconnect the first switch (51) or the second switch (52); - Apply a pre-given first reference signal and / or a pre-given second reference signal; - Analyze and process the first useful signal or the second useful signal as follows: whether there is damage to the sensor (3) or damage to the electrical connection between the sensor (3) and the electronic circuit (1), Its features are, Close the first switch (51) and open the second switch (52), then apply a positive reference signal to the first input terminal (43) and apply a negative reference signal to the second input terminal (44), and record the first useful signal. Then open the first switch (51) and close the second switch (52), then apply a positive reference signal to the first input terminal (43) and apply a negative reference signal to the second input terminal (44), and record the second useful signal. If the first useful signal and the second useful signal have different absolute values, then the sensor (3) is damaged.

2. The method according to claim 1, wherein the first sensor element (31) is arranged between the first input terminal (43) and the first signal output terminal (45), wherein, The first reference element (33) is arranged between the second input terminal (44) and the first signal output terminal (45), wherein the second reference element (34) is arranged between the first input terminal (43) and the second signal output terminal (46), wherein the second sensor element (32) is arranged between the second input terminal (44) and the second signal output terminal (46).

3. The method according to any one of claims 1 or 2, wherein, Disconnect the first switch (51) and close the second switch (52), then ground the second input terminal (44) and apply a positive reference signal to the first input terminal (43), wherein the second useful signal then contains information about the second reference element (34), wherein the information about the second reference element (34) is processed in the aspect of damage to the electrical connection between the sensor (3) and the electronic circuit (1).

4. The method according to claim 3, wherein, The first useful signal is analyzed and processed in terms of its absolute value.

5. The method according to claim 3, wherein, Then the first switch (51) is closed and the second switch (52) is opened. Then the first input terminal (43) is grounded and a positive reference signal is applied to the second input terminal (44). Then the first useful signal contains information about the first reference element (33). The information about the first reference element (33) is analyzed in terms of the damage to the electrical connection between the sensor (3) and the electronic circuit (1).

6. The method according to claim 5, wherein, The second useful signal is analyzed and processed in terms of its absolute value.

7. A computer program product comprising instructions that, when implemented by a computer, cause the computer to perform the method according to any one of claims 1 to 6.

8. A machine-readable storage medium on which a computer program product according to claim 7 is stored.

9. An electronic circuit (1) having a control logic unit (2), a sensor (3), and an amplifier (5), wherein, The sensor (3) includes a first sensor element (31) and a first reference element (33) in a first branch (41) of a Wheatstone bridge circuit (4), and a second sensor element (32) and a second reference element (34) in a second branch (42) of the Wheatstone bridge circuit (4), wherein the first branch (41) and the second branch (42) are connected in parallel, wherein the Wheatstone bridge circuit (4) has a first input terminal (43) for a first reference signal and a second input terminal (44) for a second reference signal, wherein the first input terminal (43) and the second input terminal (44) are respectively connected to the first branch (41) and the second branch (42), wherein the first reference signal and the second reference signal are provided by means of the control logic unit (2), wherein the first branch (41) has a first sensor element (31) and a second reference element (34) in a first sensor element (31) and a second reference element (34) in a second branch (42) of the Wheatstone bridge circuit (4), wherein the first sensor element (31) and the second reference element (34) are connected in parallel, ... The first signal output terminal (45) between the elements (33), the second branch (42) having a second signal output terminal (46) between the second sensor element (32) and the second reference element (34), wherein a first useful signal can be determined at the first signal output terminal (45) and a second useful signal can be determined at the second signal output terminal (46), wherein the first signal output terminal (45) is connected to the first amplifier input terminal (53) of the amplifier (5) via a first switch (51), wherein the second signal output terminal (46) is connected to the second amplifier input terminal (54) of the amplifier (5) via a second switch (52), wherein the electronic circuit (1) is configured to perform the method according to any one of claims 1 to 6 by means of the control logic unit (2), characterized in that the control logic unit (2) controls the electronic circuit (1) in such a manner as: Close the first switch (51) and open the second switch (52), then apply a positive reference signal to the first input terminal (43) and apply a negative reference signal to the second input terminal (44), and record the first useful signal. Then open the first switch (51) and close the second switch (52), then apply a positive reference signal to the first input terminal (43) and apply a negative reference signal to the second input terminal (44), and record the second useful signal. If the first useful signal and the second useful signal have different absolute values, then the sensor (3) is damaged.

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