Diagnostic device, diagnostic method, and field device

Abstract

The present disclosure provides a diagnostic apparatus, comprising: a generation circuit that generates an inspection signal, the inspection signal being a single-frequency AC signal; a conversion circuit that converts a response signal of the piezoelectric element in response to the inspection signal into a DC signal; and a controller that analyzes the DC signal and determines whether the piezoelectric element operates normally based on the analysis of the DC signal.

Description

[0001] Cross-references to related applications

[0002] This application is a divisional application of the invention patent application filed on October 22, 2021, with application number 202111232797.4 and title "Diagnostic Equipment, Diagnostic Method and Field Equipment". Technical Field

[0003] In general, the present invention relates to a diagnostic device, a diagnostic method, and a field device. Background Technology

[0004] As is well known, field devices (such as eddy current flow meters) use piezoelectric elements that convert physical quantities such as oscillations and pressure into voltage. In such field devices, the piezoelectric element is typically located inside the device. Therefore, it is necessary to be able to diagnose whether the piezoelectric element is functioning properly without removing it from the field device.

[0005] Patent document 1 describes a configuration for diagnosing piezoelectric elements.

[0006] Patent documents

[0007] Patent Document 1: JP 2005-526228 A (Translation of PCT Application)

[0008] However, in the configuration according to Patent Document 1, the circuit configuration is complex and large-scale because AC signals are applied to the piezoelectric element at at least two different frequencies and its response is measured. Summary of the Invention

[0009] One or more embodiments of the present invention provide a diagnostic device and method, as well as a field device, capable of diagnosing the health status of piezoelectric components using a simple configuration.

[0010] A diagnostic device according to several embodiments includes: a generation circuit for generating a test signal, which is a single-frequency AC signal; a conversion circuit for converting a response signal of a piezoelectric element to the test signal into a DC signal; and a control unit for analyzing the DC signal to determine the health status of the piezoelectric element. Specifically, the conversion circuit may include a half-wave rectifier. Therefore, by applying a single-frequency AC signal to the piezoelectric element and measuring its response, the diagnostic device can diagnose the health status of the piezoelectric element using a simple configuration.

[0011] In a diagnostic device according to one or more embodiments, the generation circuit generates an AC signal whose frequency does not belong to the frequency band of the electrical signal corresponding to the physical quantity output from the piezoelectric element as the inspection signal. Therefore, when the inspection signal does not affect the electrical signal corresponding to the physical quantity output from the piezoelectric element, the diagnostic device analyzes the DC signal reflecting the response of the piezoelectric element to the inspection signal and determines the health status of the piezoelectric element with respect to capacitance.

[0012] In a diagnostic device according to one or more embodiments, the control unit analyzes the DC signal to calculate the capacitance value of the piezoelectric element, and compares the capacitance value with a predetermined standard value to determine whether the piezoelectric element is operating normally, as a health status indicator of the piezoelectric element. Therefore, the diagnostic device can easily and accurately determine whether the piezoelectric element is operating normally.

[0013] In a diagnostic device according to one or more embodiments, the control unit analyzes the DC signal to calculate the capacitance value of the piezoelectric element, and determines the expected failure time of the piezoelectric element as a health status based on the calculated capacitance value and a previously calculated capacitance value. Therefore, the diagnostic device is able to predict the failure of the piezoelectric element based on past data.

[0014] The diagnostic device according to one or more embodiments further includes a storage unit for storing information related to a physical quantity measured by the piezoelectric element. The control unit, in response to receiving an electrical signal corresponding to the physical quantity output from the piezoelectric element, causes the storage unit to store a measured value of the physical quantity calculated based on the electrical signal, and outputs the measured value stored in the storage unit prior to the determination of the health status of the piezoelectric element, even as the health status of the piezoelectric element is determined. Therefore, even while determining the health status of the piezoelectric element, the measured value of the physical quantity obtained by using the piezoelectric element stored in the storage unit can be output to the user.

[0015] In a diagnostic device according to one or more embodiments, the control unit controls at least one of the generation circuit and the conversion circuit to change parameters related to the operation of at least one of the generation circuit and the conversion circuit, while analyzing the DC signal to determine the health status of the piezoelectric element. Therefore, the diagnostic device can more accurately determine whether the piezoelectric element is operating normally.

[0016] The diagnostic device according to one or more embodiments further includes a resistor between the generation circuit and the piezoelectric element. The control unit calculates the insulation resistance value of the piezoelectric element based on a diagnostic reference voltage, the output signal of the piezoelectric element with respect to the diagnostic reference voltage, and the resistance value of the resistor when the diagnostic reference voltage is applied to the piezoelectric element from the generation circuit via the resistor, and determines the health status of the piezoelectric element based on this insulation resistance value. Therefore, the health status of the piezoelectric element with respect to its insulation resistance can be diagnosed.

[0017] According to some embodiments, a field device includes the diagnostic device and the piezoelectric element. The field device also includes a plurality of piezoelectric elements, wherein the diagnostic device selects one piezoelectric element from the plurality of piezoelectric elements and diagnoses the health status of the selected piezoelectric element. Therefore, the field device is capable of diagnosing the health status of each piezoelectric element using signals from the plurality of piezoelectric elements.

[0018] The diagnostic method according to several embodiments includes: a step of generating a check signal by a generation circuit, the check signal being a single-frequency AC signal; a step of converting a response signal of a piezoelectric element in response to the check signal into a DC signal by a conversion circuit; and a step of analyzing the DC signal by a control unit to determine the health status of the piezoelectric element. Therefore, the diagnostic method can diagnose the health status of a piezoelectric element using a simple configuration.

[0019] According to one or more embodiments, a simple configuration can be used to diagnose the health status of piezoelectric elements. Attached Figure Description

[0020] Figure 1 This is a diagram illustrating an example configuration of a field device according to one or more embodiments.

[0021] Figure 2 This is a diagram showing an example of the equivalent circuit of a piezoelectric element.

[0022] Figure 3 This is a diagram showing an example configuration of a health status confirmation circuit.

[0023] Figure 4 This is a diagram illustrating a configuration example of a field device associated with another example, according to one or more embodiments.

[0024] Figure 5 This is a timing diagram illustrating an example of when to measure a piezoelectric element.

[0025] Figure 6 This is a timing diagram illustrating an example of when to diagnose the health condition of a piezoelectric element.

[0026] Figure 7 This is a flowchart illustrating an example of the operation of a diagnostic device according to one or more embodiments. Detailed Implementation

[0027] As a comparative example, Patent Document 1 discloses a diagnostic device for testing piezoelectric sensors. The diagnostic device associated with this comparative example applies AC signals to the piezoelectric sensor at at least two different frequencies and measures the response signal generated by the piezoelectric sensor in response to the applied AC signals. Furthermore, the diagnostic device associated with this comparative example diagnoses the state of the piezoelectric sensor based on the measured output.

[0028] However, the diagnostic equipment associated with the comparative example must apply AC signals to the piezoelectric sensor at at least two different frequencies, thus making the circuit configuration complex and large-scale.

[0029] Embodiments of the present disclosure are described below with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the description of these embodiments, the description of the same or corresponding parts is appropriately omitted or simplified.

[0030] (First embodiment)

[0031] Figure 1 This diagram illustrates a configuration example of a field device 100 according to a first embodiment. The field device 100 includes a diagnostic device 10 and a piezoelectric element 90. In the field device 100, the diagnostic device 10 receives measurement signals related to physical quantities (e.g., oscillations or pressure) from the piezoelectric element 90, calculates the flow rate of liquids, gases, etc., and diagnoses whether the piezoelectric element 90 is operating normally (healthily). The diagnostic device 10 includes a microcontroller 11 (controller), a ROM (read-only memory) 12, a RAM (random access memory) 13, an output circuit / communication circuit 14, a display device 15, a check signal generation circuit 16, a resistor 17, an amplifier circuit 18, a filter circuit 19, an A / D (analog-to-digital) conversion circuit 20, a health status confirmation circuit 21, and an A / D conversion circuit 22. For example, the field device 100 includes a flow meter, a pressure gauge, etc., equipped with the piezoelectric element 90.

[0032] The microcontroller 11 acts as a control unit to control the operation of the entire field device 100. The microcontroller 11 includes one or more processors. In one or more embodiments, a "processor" is a general-purpose processor or a dedicated processor for a specific process, but is not limited thereto.

[0033] ROM 12 is a read-only memory that stores system programs, data, etc., required to control the field device 100. RAM 13 is a writable memory that can be used as a main storage device, an auxiliary storage device, or a cache memory. RAM 13 can store various information, such as system programs, application programs, and measurement data measured by the piezoelectric element. ROM 12 and RAM 13 are used as storage units to store information related to the physical quantities measured by the piezoelectric element 90.

[0034] The output circuit / communication circuit 14 includes any communication module capable of communicating with other devices such as a PC (personal computer) via any communication technology. The output circuit / communication circuit 14 may also include a communication control module for controlling communication with other devices and a storage module for storing communication data required for communicating with other devices.

[0035] Display device 15 displays information to the user as a display unit. Display device 15 displays information such as indicators of physical quantities measured by piezoelectric element 90, the health status of piezoelectric element 90, etc. Display device 15 may be implemented, for example, as a liquid crystal display (LCD), an instrument, etc.

[0036] When the piezoelectric element 90 is used as a sensor in the field device 100, the electrical signal generated from the piezoelectric element 90 is typically output as an electrical signal belonging to a specific frequency band corresponding to the measurement target. According to one or more embodiments, the field device 100 inputs the electrical signal output from the piezoelectric element 90 to a microcontroller 11 via an amplifier circuit 18, a filter circuit 19, and an A / D conversion circuit 20, where the microcontroller 11 converts the electrical signal into a physical quantity corresponding to the electrical signal.

[0037] Amplifier circuit 18 amplifies the amplitude of the electrical signal output from piezoelectric element 90. The amplified electrical signal is then output to filter circuit 19.

[0038] The filter circuit 19 allows only signals within a predetermined frequency band to pass through the electrical signal output from the amplifier circuit 18, and performs filtering to attenuate signals belonging to other frequency bands. The filter circuit 19 is implemented using an LPF (low-pass filter), HPF (high-pass filter), BPF (band-pass filter), BEF (band-stop filter), or a combination thereof. The filtered electrical signal is output to the A / D conversion circuit 20.

[0039] The A / D conversion circuit 20 converts the electrical signal, which is input as an analog signal, into a digital signal. The converted digital signal is then output to the microcontroller 11.

[0040] The microcontroller 11 converts the digital electrical signal input from the A / D conversion circuit 20 into a corresponding physical quantity. For example, when the piezoelectric element 90 is used in an eddy current flow meter, the microcontroller 11 converts the input electrical signal into the amount of fluid movement per unit time (flow rate or velocity). The conversion from electrical signal to physical quantity is performed according to a program pre-stored in ROM 12 or RAM 13. The microcontroller 11 displays the obtained physical quantity on the display device 15 for user confirmation. Alternatively, the microcontroller 11 can use the output circuit / communication circuit 14 to output the acquired physical quantity to another device, allowing the user to confirm the physical quantity.

[0041] Simultaneously, when diagnosing whether the piezoelectric element 90 is operating normally, the microcontroller 11 generates a single-frequency check signal (a pulse wave from the check signal generation circuit 16) and inputs the check signal to the piezoelectric element 90 via resistor 17. The response signal of the piezoelectric element 90 to the check signal is input to the microcontroller 11 via the health status confirmation circuit 21 and the A / D conversion circuit 22. The microcontroller 11 determines whether the piezoelectric element 90 is operating normally based on the response signal, which is the transient response of the piezoelectric element 90 to the check signal.

[0042] The check signal generation circuit 16, acting as a generation circuit, generates a single-frequency check signal, controlled by the microcontroller 11, to check whether the piezoelectric element 90 is operating normally. The check signal is, for example, an AC signal whose frequency does not belong to the frequency band of the electrical signal output from the piezoelectric element 90 based on the measured value of the physical quantity. The check signal can also be, for example, an AC signal whose frequency is sufficiently separated from the frequency band of the electrical signal corresponding to the measured value of the physical quantity. When the field device 100 is used, for example, as an eddy current flow meter to measure the flow rate of fluid moving in a pipe, the frequency of the check signal can be set to the same value (e.g., 12.8 kHz) regardless of the pipe thickness (inner diameter, etc.). The check signal generated in the check signal generation circuit 16 is output to the resistor 17.

[0043] Resistor 17 is a resistor with a pre-known resistance value. Resistor 17 can have a high resistance, for example, 10 MΩ. The check signal output from check signal generation circuit 16 to resistor 17 is output to piezoelectric element 90 after passing through resistor 17.

[0044] The piezoelectric element 90 is a component that generates electrical signals based on mechanical motion (such as oscillation, pressure, etc.). Figure 2 This is a diagram showing an example of the equivalent circuit of the piezoelectric element 90. (See diagram for example.) Figure 2 As shown, the piezoelectric element 90 can be manufactured as an insulation resistor R 93, a capacitor C 92 connected in parallel with the insulation resistor R 93, and a voltage source E. S91. When the piezoelectric element 90 is operating normally, the insulation resistance R 93 is, for example, 50 kΩ, and the capacitance C 92 is, for example, 30 pF or less. When a check signal is input to the piezoelectric element 90, the response signal of the piezoelectric element 90 to the check signal is output to the health status confirmation circuit 21 as a voltage between terminals 94 or a current flowing between terminals 94.

[0045] The response signal of the piezoelectric element 90 to the check signal is also output to the amplifier circuit 18. However, as mentioned above, the frequency of the check signal does not belong to the frequency band of the electrical signal output from the piezoelectric element 90 corresponding to the measured value of the physical quantity. Therefore, the filter circuit 19 removes the response signal of the piezoelectric element 90 to the check signal from the amplifier circuit 18.

[0046] As a health status confirmation circuit, the conversion circuit 21 converts the response signal of the piezoelectric element 90 into a DC signal that reflects the resistance value of the insulation resistor R 93 and the capacitance value of the capacitor C 92. Figure 3 This is a diagram showing an example configuration of the health status verification circuit 21. The health status verification circuit 21 includes an HPF half-wave rectifier 211 and an LPF amplifier circuit 212.

[0047] The HPF half-wave rectifier 211 extracts frequency components above a predetermined threshold from the response signal of the piezoelectric element 90 to the check signal. Furthermore, the HPF half-wave rectifier 211 performs half-wave rectification on the high-frequency components of the response signal. The HPF half-wave rectifier 211 can be implemented, for example, using an operational amplifier. The processed response signal is output to the LPF amplifier circuit 212.

[0048] The LPF amplifier circuit 212 extracts frequency components below a predetermined threshold from the response signal input from the HPF half-wave rectifier 211. Furthermore, the LPF amplifier circuit 212 amplifies the amplitude of the low-frequency components of the response signal. The processing by the HPF half-wave rectifier 211 and the LPF amplifier circuit 212 is equivalent to converting the response signal, which is an AC signal, into a DC signal. The processed response signal is then output to the A / D conversion circuit 22.

[0049] The A / D conversion circuit 22 converts the response signal, which is input as an analog signal, into a digital signal. The converted digital response signal is then output to the microcontroller 11.

[0050] When a diagnostic reference voltage is applied from the check signal generation circuit 16 via resistor 17, the microcontroller 11 obtains the output voltage from the piezoelectric element 90 via the amplifier circuit 18, the filter circuit 19, and the A / D conversion circuit 20. The diagnostic reference voltage is the voltage between the output terminal of the check signal generation circuit 16 and the ground terminal of the piezoelectric element 90, and can be set to a DC voltage. The output voltage of the piezoelectric element 90 is the voltage obtained by dividing the diagnostic reference voltage by the insulation resistor R 93 of the piezoelectric element 90 and the resistance of resistor 17. Therefore, the microcontroller 11 can calculate the resistance value of the insulation resistor R 93 of the piezoelectric element 90 based on the output voltage of the piezoelectric element 90, the known diagnostic reference voltage, and the known resistance value of resistor 17. Typically, the insulation resistor R 93 has a resistance value of, for example, several MΩ, which is a portion of the resistance value of resistor 17 (e.g., 10 MΩ). In abnormal conditions, the insulation resistor R 93 has a resistance value of, for example, tens of kΩ or less. Therefore, in this case, the output voltage usually displays a value that is a portion of the diagnostic reference voltage, but in abnormal situations it displays a value that is very close to 0 V.

[0051] Furthermore, the microcontroller 11 applies a pulse signal as an AC signal to the piezoelectric element 90 and analyzes the response signal, which is converted into a DC signal reflecting the capacitance value of the capacitor C 92 in the health status confirmation circuit 21. When the frequency of the check signal as a pulse wave is f and the capacitance value of the capacitor C 92 is C, the impedance of the capacitor is 1 / (2πf×C). Then, based on this relationship, the microcontroller 11 calculates the capacitance value of the capacitor C 92 from the voltage value of the check signal and the voltage value of the piezoelectric element 90's response signal to the check signal.

[0052] The microcontroller 11 determines the health status of the piezoelectric element 90 based on at least one of the resistance value of the insulation resistor R 93 and the capacitance value of the capacitor C 92, obtained by analyzing the response signal. Specifically, the microcontroller 11 compares, for example, preset values ​​for the resistance of the insulation resistor R 93 and the capacitance of the capacitor C 92 (e.g., 50 kΩ for the insulation resistor and 30 pF for the capacitance) with values ​​calculated by analyzing the response signal. The microcontroller 11 can then determine that the piezoelectric element 90 is faulty if the difference between the two values ​​exceeds a predetermined value, and can determine that the piezoelectric element 90 is operating normally if the difference is within the predetermined value. For example, the microcontroller 11 can determine that the piezoelectric element 90 is faulty when the resistance value calculated based on the response signal is lower than a preset standard value, or when the capacitance value calculated based on the response signal is higher than a preset standard value.

[0053] Alternatively, the microcontroller 11 may, for example, compare the value of at least one of the resistance value of the insulation resistor R 93 and the capacitance value of the capacitor C 92 obtained through previous measurements with a value calculated by analyzing the response signal. In this case, the microcontroller 11 may, for example, determine that the piezoelectric element 90 is faulty if the difference between the resistance value or capacitance value calculated based on the response signal and the previously measured value is higher than a predetermined standard value.

[0054] Alternatively, the microcontroller 11 may, for example, store the value of at least one of the resistance value of the insulation resistor R 93 and the capacitance value of the capacitor C 92 obtained through previous measurements in the ROM 12 or RAM 13. Then, the microcontroller 11 may, for example, determine that the piezoelectric element 90 is faulty when the resistance or capacitance value calculated based on the response signal is inconsistent with the trend of change stored in the ROM 12 or RAM 13. Further, the microcontroller 11 may predict the time when the piezoelectric element 90 will fail based on the resistance or capacitance value calculated according to the response signal and trend data (resistance or capacitance values ​​calculated in the past). Specifically, for example, the microcontroller 11 may predict the time of failure by estimating the change in resistance or capacitance value based on the slope of a graph showing the changes in resistance or capacitance value calculated in the past for a single piezoelectric element 90. Alternatively, for example, the microcontroller 11 may predict the time of failure by estimating the change in resistance or capacitance value based on the average value or slope of the curves showing the changes in resistance or capacitance value calculated in the past for multiple piezoelectric elements 90. Furthermore, when the field device 100 is used as an eddy current flow meter, the microcontroller 11 can perform machine learning, for example, using the insulation resistance and capacitance of the piezoelectric element 90, the usage status of the piezoelectric element 90, and information about faults as training data. The microcontroller 11 can then generate and utilize a predictive model for predicting the failure time of the piezoelectric element 90 through such machine learning.

[0055] After determining the health status of the piezoelectric element 90, the microcontroller 11 outputs the result to the outside via the display device 15 or the output circuit / communication circuit 14. Users can identify whether the piezoelectric element 90 is operating normally by confirming the health status determination result. Users can also perform predictive diagnostics based on changes in insulation resistance or capacitance to determine whether the piezoelectric element 90 will fail and requires replacement.

[0056] Note that some or all of the functions of the diagnostic device 10 can be implemented by using a processor included in the microcontroller 11 to execute a program according to one or more embodiments. That is, some or all of the functions of the diagnostic device 10 can be implemented by software. The program causes a computer to perform processing including steps in the operation of the diagnostic device 10, enabling the computer to perform a function corresponding to each step of the processing. In other words, the program is used to enable the computer to function as the diagnostic device 10 according to one or more embodiments.

[0057] As described above, in the diagnostic device 10, the check signal generation circuit 16 generates a check signal, which is a single-frequency AC signal. The health status confirmation circuit 21 converts the response signal of the piezoelectric element 90 to the check signal into a DC signal. Specifically, the health status confirmation circuit 21 converts the response signal into a DC signal via an HPF half-wave rectifier 211. The microcontroller 11 analyzes the DC signal to determine the health status of the piezoelectric element 90. Specifically, the microcontroller 11 calculates the current flowing through the piezoelectric element 90 and the voltage between the terminals based on the voltage and current values ​​in the resistor 17, and calculates the insulation resistance value of the piezoelectric element 90. Furthermore, the microcontroller 11 analyzes the DC signal to calculate the capacitance value of the piezoelectric element 90. Further, the microcontroller 11 compares the calculated value with a predetermined standard value to determine whether the piezoelectric element 90 is operating normally, as its health status. Therefore, by applying a check signal as a single AC signal, the diagnostic device 10 can easily and accurately confirm the health status of the piezoelectric element 90 with a simpler circuit configuration.

[0058] Furthermore, the microcontroller 11 can calculate at least one of the insulation resistance or capacitance values ​​of the piezoelectric element 90, and determine the health status of the piezoelectric element 90 based on this value and previously calculated past insulation resistance and capacitance values. Therefore, the microcontroller 11 is able to determine the predicted failure time for the piezoelectric element 90 as its health status.

[0059] Furthermore, the check signal generation circuit 16 generates an AC signal whose frequency does not belong to the frequency band of the electrical signal output from the piezoelectric element 90 based on the physical quantity, as a check signal. Therefore, the diagnostic device 10 can analyze the response signal (a DC signal reflecting the capacitance value of the capacitor C 92) without the check signal affecting the measurement signal output from the piezoelectric element 90, and determine the health status of the piezoelectric element 90 with respect to capacitor C 92. Thus, the increased scale and reduced circuit configuration responsiveness due to multiple operating modes, as well as the necessity for special operations and processes, are suppressed, and usability to the user is significantly improved.

[0060] (Second Embodiment)

[0061] Figure 1The field device 100 shown has one piezoelectric element 90, but field devices with multiple piezoelectric elements 90 can be provided. Figure 4 This is a diagram illustrating an example configuration of a field device 200 according to a second embodiment. The field device includes two piezoelectric elements A 90a and B 90b, and a diagnostic device 30. Figure 1 The configurations in the figures are similar, and the functions and components used for operation are referred to by the same reference numerals, and their detailed descriptions are omitted.

[0062] The diagnostic device 30 includes a microcontroller 11, a ROM 12, a RAM 13, an output circuit / communication circuit 14, a display device 15, a test signal generation circuit 16, a resistor 17, an amplifier circuit A 18a, an amplifier circuit B 18b, a filter circuit A 19a, a filter circuit B 19b, an A / D conversion circuit A 20a, an A / D conversion circuit B 20b, a health status confirmation circuit 21, and an A / D conversion circuit 22.

[0063] The electrical signal output from piezoelectric element A 90a is input to microcontroller 11 via amplifier circuit A 18a, filter circuit A 19a, and A / D conversion circuit A 20a, where it is converted into a physical quantity corresponding to the electrical signal. The electrical signal output from piezoelectric element B 90b is input to microcontroller 11 via amplifier circuit B 18b, filter circuit B 19b, and A / D conversion circuit B 20b, where it is converted into a physical quantity corresponding to the electrical signal. The operation of amplifier circuits A 18a, B 18b, A 19a, B 19b, A / D conversion circuits A 20a and B 20b is similar to that of amplifier circuit 18, filter circuit 19, and A / D conversion circuit 20. Therefore, in a configuration that uses multiple piezoelectric elements (piezoelectric element A 90a and piezoelectric element B 90b) to measure physical quantities more accurately, the field device 200 is able to diagnose the health status of each piezoelectric element by using response signals to the inspection signals obtained from the multiple piezoelectric elements.

[0064] Furthermore, when diagnosing whether piezoelectric elements A 90a and B 90b are functioning correctly, field device 200 generates a check signal in check signal generation circuit 16, similar to field device 100. Field device 200 outputs the generated check signal to piezoelectric elements A 90a and B 90b via resistor 17. When the check signal is output to piezoelectric elements A 90a and B 90b, it is necessary to distinguish between the response signal from piezoelectric element A 90a and the response signal from piezoelectric element B 90b. Therefore, a switch is provided between resistor 17 and piezoelectric elements A 90a and B 90b, and microcontroller 11 can apply a check signal to one of the piezoelectric elements by switching the switch in conjunction with the output of the check signal from check signal generation circuit 16. Alternatively, the microcontroller 11 can control the check signal generation circuit 16 to select the piezoelectric element 90 as the output destination of the check signal, and control the check signal generation circuit 16 to output the check signal to the selected piezoelectric element 90. Alternatively, the microcontroller 11 can control the check signal generation circuit 16 to vary the timing of the output to piezoelectric element A 90a and the output to piezoelectric element B 90b. The health status confirmation circuit 21 converts the response signal to the check signal obtained from piezoelectric element A 90a or piezoelectric element B 90b into a DC signal, and outputs this DC signal to the microcontroller 11 via the A / D conversion circuit 22. Similar to the field device 100, the microcontroller 11 diagnoses whether piezoelectric elements A 90a and B 90b are operating normally based on the response signal. Therefore, according to... Figure 4 The configuration allows it to determine whether each of the piezoelectric elements 90a and 90b is functioning correctly, even in a field device 200 equipped with multiple piezoelectric elements 90a and 90b.

[0065] (Third embodiment)

[0066] The diagnostic device 10 cannot diagnose the health status related to the capacitance value C92 of the piezoelectric element 90 while the piezoelectric element 90 is outputting a measurement signal. Therefore, the microcontroller 11 must control each component such that the timing of determining the health status related to the capacitance value C92 of the piezoelectric element 90 differs from the timing of the piezoelectric element 90 measuring the physical quantity. However, when the diagnostic device 10 is used in a field device 100, such as an eddy current flowmeter, the measurement and display of the physical quantity do not need to be highly responsive, and from the user's point of view, even a delay of a few seconds between measurement and display is generally not a problem. Therefore, in the third embodiment, the microcontroller 11 saves the physical quantity measured by the measurement mode to RAM 13 before switching from a measurement mode for measuring the physical quantity to a diagnostic mode for determining the health status related to the capacitance value of the piezoelectric element 90. Furthermore, the microcontroller 11 continuously outputs the physical quantity stored in RAM 13 and displays the physical quantity on the display device 15 even in diagnostic mode. Therefore, even if the measured value of a physical quantity fluctuates due to a diagnosis of health condition, the diagnostic device 10 in the third embodiment can be displayed as if it can simultaneously perform the measurement of the physical quantity and the diagnosis related to the capacitance value of the piezoelectric element 90, without displaying the fluctuation to the user.

[0067] Figure 5 This is a timing diagram illustrating an example of when to measure the piezoelectric element 90. Figure 5 In the example, the piezoelectric element 90 measures the physical quantity six times with a period of 250 ms. The microcontroller 11 stores the measured value of the physical quantity measured by each measurement mode (measurement 1 to measurement 6) in RAM 13. Furthermore, the microcontroller 11 displays the latest measured value of the physical quantity on the display device 15. Thus, the user can confirm the latest measured value of the physical quantity. In the third embodiment, the microcontroller 11 controls the check signal generation circuit 16 such that no check signal is generated during the measurement mode in which the physical quantity is measured by the piezoelectric element 90.

[0068] Figure 6 This is a timing diagram illustrating an example of when to diagnose the health condition of the piezoelectric element 90. Figure 6In the example shown, after the measurement mode shown in Measurement 1, the health status of the piezoelectric element 90 is diagnosed based on the response to the check signal in the diagnostic mode (Diagnosis 1) for 1000 ms (1 second). In the third embodiment, the physical quantity measured in Measurement 1 is stored in RAM 13 during Measurement 1. Therefore, even during the diagnostic mode of Diagnosis 1, the microcontroller 11 continuously displays the measured value of the physical quantity under Measurement 1 on the display device 15. That is, while the health status of the piezoelectric element 90 is determined, the microcontroller 11 outputs the measured value of the physical quantity stored in RAM 13 before the health status determination and displays the measured value on the display device 15. Therefore, the measured value of the physical quantity stored in RAM 13 can be output and displayed even while the health status of the piezoelectric element is being determined.

[0069] (Fourth embodiment)

[0070] In the fourth embodiment, when diagnosing the health status of the piezoelectric element 90 in diagnostic mode, the diagnostic device 10 can more easily detect faults in the piezoelectric element 90 by changing parameters related to the operation of at least one of the inspection signal generation circuit 16 and the health status confirmation circuit 21 while observing the response signal from the piezoelectric element 90. As specific parameters to be changed, at least one of the frequency and voltage of the inspection signal generation circuit 16 and a constant of the health status confirmation circuit 21 are considered.

[0071] In other words, the microcontroller 11 can make at least one of the frequency and amplitude of the check signal generation circuit 16 a variable parameter related to the operation of the check signal generation circuit 16 during diagnosis. The response signal to the check signal obtained from the piezoelectric element 90 typically shows the expected behavior, but exhibits unexpected behavior under abnormal conditions (e.g., when a fault occurs in the piezoelectric element 90). Therefore, the microcontroller 11 can easily detect such anomalies in the piezoelectric element 90 by changing the frequency and amplitude. The microcontroller 11 stores, for example, the normal behavior when the frequency and amplitude change in ROM 12 or RAM 13 and compares it with the response signal from the piezoelectric element 90. Since different behavior is shown under abnormal conditions, the microcontroller 11 can detect the anomaly based on the time difference in the response behavior. Furthermore, parameters related to the operation of the check signal generation circuit 16, such as the power supply voltage value of the check signal generation circuit 16, can also be considered.

[0072] Alternatively, during diagnosis, the microcontroller 11 can change the constant of the health status verification circuit 21 as a parameter related to the operation of the health status verification circuit 21, and confirm the health status of the piezoelectric element 90 based on the behavior of the response signal of the piezoelectric element 90 changing with the constant. The microcontroller 11 can change the waveform of the output of the HPF half-wave rectifier 211 by changing the feedback rate of the operational amplifier of the HPF half-wave rectifier 211 as a constant of the health status verification circuit 21. For example, the microcontroller 11 can change the feedback rate of the operational amplifier so that a DC voltage (e.g., positive DC voltage) is output from the health status verification circuit 21 when the piezoelectric element 90 is operating normally, but no output (e.g., zero volts) is made when there is an abnormality. Therefore, the microcontroller 11 can easily detect abnormalities in the piezoelectric element 90 by changing the operational amplifier. Furthermore, parameters related to the operation of the health status verification circuit 21, such as the power supply voltage value of the health status verification circuit 21, can also be considered.

[0073] <Example of operation>

[0074] Reference Figure 7 The operation of the diagnostic device 10 according to one or more embodiments is described. Figure 7 This is a flowchart illustrating an example of the operation of a diagnostic device 10 according to one or more embodiments. (Refer to...) Figure 7 The operation of the described diagnostic device 10 corresponds to the diagnostic method associated with this embodiment. Figure 7 Each step of the operation is performed based on the control of the microcontroller 11, which acts as the control unit. The program for causing the computer to perform the diagnostic method related to this embodiment includes... Figure 7 The steps are shown.

[0075] In step S1, the microcontroller 11 controls the check signal generation circuit 16 to generate a check signal. The check signal is output to the piezoelectric element 90 via the resistor 17.

[0076] In step S2, the microcontroller 11 causes the health status verification circuit 21 to receive the response signal from the piezoelectric element 90. Further, the health status verification circuit 21 converts the response signal from the piezoelectric element 90 to the check signal into a DC signal. The converted DC response signal is output to the microcontroller 11 via the A / D conversion circuit 22.

[0077] In step S3, the microcontroller 11 analyzes the DC signal to determine the health status of the piezoelectric element 90. Details of each step are as described above.

[0078] Therefore, the diagnostic device 10 can use a simple configuration to diagnose the health status of the piezoelectric element 90.

[0079] Although this disclosure has described only a limited number of embodiments, those skilled in the art will recognize, with the benefit of this disclosure, that various other embodiments can be devised without departing from the scope of the invention. Therefore, the scope of the invention should be defined only by the appended claims.

[0080] 10, 30 Diagnostic equipment

[0081] 11 Microcontrollers

[0082] 12 ROM

[0083] 13 RAM

[0084] 14 Output Circuit / Communication Circuit

[0085] 15 Display devices

[0086] 16. Inspect the signal generation circuit.

[0087] 17 Resistors

[0088] Amplifier circuits 18, 18a, and 18b

[0089] Filter circuits 19, 19a, and 19b

[0090] 20, 20a, 20b A / D conversion circuits

[0091] 21 Health Status Confirmation Circuit

[0092] 22 A / D Conversion Circuit

[0093] 90, 90a, 90b piezoelectric elements

[0094] 91 Voltage Source

[0095] 92 capacitors

[0096] 93 Insulation Resistors

[0097] Between 94 terminals

[0098] 100, 200 field equipment

[0099] 211 HPF Half-Wave Rectifier

[0100] 212 LPF amplifier circuit

Claims

1. A field device, comprising: The generation circuit generates a check signal, which is a single-frequency AC signal. A conversion circuit that converts the piezoelectric element's response signal to the inspection signal into a DC signal, and The controller, the controller: Analyze the DC signal; and Based on the analysis of the DC signal, the health status of the piezoelectric element is determined, wherein... The controller determines the health status of the piezoelectric element by analyzing the DC signal and calculating the capacitance value of the piezoelectric element.

2. The field device according to claim 1, wherein, The conversion circuit includes a half-wave rectifier.

3. The field device according to claim 1 or 2, wherein, The inspection signal is an AC signal whose frequency does not belong to the frequency band of the electrical signal output from the piezoelectric element based on the physical quantity.

4. The field device according to any one of claims 1 to 3, wherein, The controller also includes: The DC signal is analyzed to calculate the capacitance value of the piezoelectric element; The capacitance value is compared with a predetermined standard value; and Based on the results of the comparison, the health status of the piezoelectric element is determined.

5. The field device according to any one of claims 1 to 3, wherein, The controller also includes: Analyze the DC signal to calculate the capacitance value of the piezoelectric element; and Based on the calculated capacitance value and the previously calculated capacitance value, the expected failure time of the piezoelectric element is determined.

6. The field device according to claim 5, wherein, The controller determines the predicted failure time of the piezoelectric element as the health status based on the slope of a graph showing the change in the previously calculated capacitance value of the piezoelectric element.

7. The field device according to claim 5, wherein, The controller determines the predicted failure time of the piezoelectric element as the health status based on the slope or average change of a graph showing the changes in previously calculated capacitance values ​​of the multiple piezoelectric elements.

8. The field device according to any one of claims 1 to 7, further comprising: A memory that stores information related to physical quantities measured by the piezoelectric element, wherein, In response to receiving an electrical signal corresponding to a physical quantity output from the piezoelectric element, the controller causes the memory to store the measured value of the physical quantity calculated based on the electrical signal, and While determining the health status of the piezoelectric element, the controller outputs the measurement value stored in the memory just before determining the health status of the piezoelectric element.

9. The field device according to any one of claims 1 to 8, wherein, The controller also includes: Controlling the operation of at least one of the generation circuit or the conversion circuit; While analyzing the DC signal, the parameters related to the operation are changed; The health status of the piezoelectric element is determined based on the changed parameters.

10. The field device according to any one of claims 1 to 9, further comprising: A resistor, located between the generating circuit and the piezoelectric element, wherein, The controller: Based on the diagnostic reference voltage, the output signal of the piezoelectric element with respect to the diagnostic reference voltage, and the resistance value of the resistor when the diagnostic reference voltage is applied to the piezoelectric element from the generation circuit via the resistor, the insulation resistance value of the piezoelectric element is calculated; and The health status of the piezoelectric element is determined based on the insulation resistance value.

11. The field device according to any one of claims 1 to 10, comprising a plurality of piezoelectric elements, wherein, The controller selects one piezoelectric element from the plurality of piezoelectric elements and determines the health status of that piezoelectric element.

12. The field device according to claim 8, further comprising a display device, wherein, The display device displays the measured values ​​output by the controller.

13. A diagnostic method, comprising: Generate a check signal, which is a single-frequency AC signal; The response signal of the piezoelectric element to the inspection signal is converted into a DC signal, and Analyze the DC signal and determine the health status of the piezoelectric element, wherein The health status of the piezoelectric element is determined by analyzing the DC signal and calculating the capacitance value of the piezoelectric element.

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