A threshold-adaptive frequency measurement circuit and device

Abstract

This application discloses a threshold-adaptive frequency measurement circuit and device, applicable to the field of frequency measurement. The threshold-adaptive frequency measurement circuit provided in this application includes: a filter circuit, a charging circuit, and a hysteresis comparator module. The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, and is used to charge the charging circuit. The hysteresis comparator module is connected to the charging circuit, the filter circuit, and an FPGA, and is used to adjust the comparison threshold according to the voltage of the charging circuit. The frequency measurement method of this application can adaptively adjust the comparison voltage threshold based on the signal amplitude, filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine.

Description

Technical Field

[0001] This application relates to the field of frequency measurement, and in particular to a threshold-adaptive frequency measurement circuit and device. Background Technology

[0002] In the DEH control of steam turbines, rotational speed is a crucial parameter that needs to be measured, as it directly affects the turbine's control and protection circuits. Rotational speed is measured using a magnetoresistive sensor mounted on the turbine's main shaft. As the turbine rotates, the magnetoresistive sensor generates an alternating sine wave whose amplitude and frequency vary with the rotational speed.

[0003] Currently, the industry generally uses a fixed comparison threshold method to detect the speed of steam turbines. However, in actual operation, the speed sensor and the frequency measurement module are connected by a long cable, and the cable is laid in a uniform cable tray. There are different types of cables in the cable tray, which inevitably cause signal crosstalk, resulting in abnormal fluctuations in the speed signal. This leads to a large speed measurement error or even double the error, affecting the operation of the steam turbine.

[0004] Given the above-mentioned technologies, finding a threshold-adaptive frequency measurement circuit is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a threshold-adaptive frequency measurement circuit and device that can adjust the comparison threshold according to the voltage, filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine.

[0006] To solve the above technical problems, this application provides a threshold adaptive frequency measurement circuit, including: a filter circuit, a charging circuit, and a hysteresis comparator module;

[0007] The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, respectively, and is used to charge the charging circuit.

[0008] The hysteresis comparator module is connected to the charging circuit, the filtering circuit, and the FPGA, respectively, and is used to adjust the comparison threshold according to the voltage of the charging circuit.

[0009] Preferably, the filter circuit includes a positive protection circuit, a negative protection circuit, a first subtractor circuit, a first-order inertial filter circuit, a second subtractor circuit, and a third subtractor circuit, used to charge the charging circuit.

[0010] The first input terminal of the first subtractor circuit is connected to the non-inverting output terminal of the sensor, the second input terminal of the first subtractor circuit is connected to the inverting output terminal of the sensor, and the output terminal of the first subtractor circuit is connected to the input terminal of the first-order inertial filter circuit, the first input terminal of the second subtractor circuit, and the first input terminal of the third subtractor circuit.

[0011] The positive protection circuit is connected to the non-inverting output terminal of the sensor and the first input terminal of the first subtractor circuit;

[0012] The negative protection circuit is connected to the inverted output terminal of the sensor and the second input terminal of the first subtractor circuit;

[0013] The output of the first-order inertial filter circuit is connected to the second input of the second subtractor circuit and the second input of the third subtractor circuit.

[0014] The output of the second subtractor circuit is connected to the first input of the charging circuit and the first input of the hysteresis comparator module.

[0015] The output of the third subtractor circuit is connected to the second input of the charging circuit and the first input of the hysteresis comparator module.

[0016] Preferably, the hysteresis comparator module includes: a first hysteresis comparator circuit, a second hysteresis comparator circuit, and an adjustment circuit for adjusting the comparison threshold value according to the voltage of the charging circuit.

[0017] Wherein, the first input terminal of the first hysteresis comparator circuit is connected to the output terminal of the second subtractor circuit, the second input terminal of the first hysteresis comparator circuit is connected to the output terminal of the adjustment circuit, and the output terminal of the first hysteresis comparator circuit is connected to the FPGA.

[0018] The first input of the second hysteresis comparator circuit is connected to the output of the third subtractor circuit, the second input of the second hysteresis comparator circuit is connected to the output of the adjustment circuit, and the output of the second hysteresis comparator circuit is connected to the FPGA.

[0019] The input terminal of the regulating circuit is connected to the output terminal of the charging circuit.

[0020] Preferably, the first subtractor circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor;

[0021] Wherein, the first end of the first resistor is connected to the non-inverting input terminal of the sensor, and the second end of the first resistor is connected to the positive protection circuit, the inverting input terminal of the first operational amplifier, and the first end of the second resistor;

[0022] The second end of the second resistor is connected to the output of the first operational amplifier;

[0023] The first end of the third resistor is connected to the inverting input terminal of the sensor, and the second end of the third resistor is connected to the negative protection circuit, the non-inverting input terminal of the first operational amplifier, and the first end of the fourth resistor.

[0024] The second terminal of the fourth resistor is grounded.

[0025] Preferably, the first-order inertial filter circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor, and a first capacitor;

[0026] The first end of the fifth resistor is connected to the output terminal of the first operational amplifier and the second end of the second resistor, and the second end of the fifth resistor is connected to the first end of the first capacitor and the non-inverting input terminal of the second operational amplifier.

[0027] The second terminal of the first capacitor is grounded;

[0028] The first end of the sixth resistor is connected to the inverting input of the second operational amplifier, and the second end of the sixth resistor is connected to the output of the second operational amplifier.

[0029] Preferably, the second subtractor circuit includes: a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor.

[0030] The first end of the seventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor; the second end of the seventh resistor is connected to the first end of the eighth resistor and the inverting input terminal of the third operational amplifier.

[0031] The second terminal of the eighth resistor is connected to the output terminal of the third operational amplifier;

[0032] The first end of the ninth resistor is connected to the second end of the sixth resistor and the output terminal of the second operational amplifier; the second end of the ninth resistor is connected to the first end of the tenth resistor and the non-inverting input terminal of the third operational amplifier.

[0033] The second terminal of the tenth resistor is grounded;

[0034] The third subtractor circuit includes: a fourth operational amplifier, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a fourteenth resistor.

[0035] Among them, the first end of the eleventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the non-inverting input terminal of the fourth operational amplifier.

[0036] The second terminal of the twelfth resistor is grounded;

[0037] The first end of the thirteenth resistor is connected to the second end of the sixth resistor, the output of the second operational amplifier, and the first end of the ninth resistor. The second end of the thirteenth resistor is connected to the first end of the fourteenth resistor and the inverting input of the fourth operational amplifier.

[0038] Preferably, the charging circuit includes a first diode, a second diode, a fifteenth resistor, a sixteenth resistor, and a second capacitor;

[0039] The first end of the first diode is connected to the second end of the fourteenth resistor and the output end of the fourth operational amplifier, and the second end of the first diode is connected to the first end of the fifteenth resistor.

[0040] The second end of the fifteenth resistor is connected to the first end of the sixteenth resistor and the first end of the second capacitor;

[0041] The second terminal of the sixteenth resistor is connected to the first terminal of the second diode;

[0042] The second terminal of the second diode is connected to the second terminal of the eighth resistor and the output terminal of the third operational amplifier;

[0043] The second terminal of the second capacitor is grounded.

[0044] Preferably, the first hysteresis comparator circuit includes: a first comparator, a seventeenth resistor, an eighteenth resistor, and a third diode;

[0045] The first end of the seventeenth resistor is connected to the second end of the second diode, the second end of the eighth resistor, and the output terminal of the third operational amplifier. The second end of the seventeenth resistor is connected to the first end of the eighteenth resistor, the first end of the third diode, and the non-inverting input terminal of the first comparator.

[0046] The second end of the eighteenth resistor is connected to the output of the first comparator;

[0047] The second terminal of the third diode is grounded;

[0048] The inverting input of the first comparator is connected to the output of the adjustment circuit.

[0049] The second hysteresis comparator circuit includes: a second comparator, a nineteenth resistor, a twentieth resistor, and a fourth diode;

[0050] Among them, the first end of the nineteenth resistor is connected to the second end of the fourteenth resistor and the output terminal of the fourth operational amplifier, and the second end of the nineteenth resistor is connected to the first end of the fourth diode, the first end of the twentieth resistor, and the non-inverting input terminal of the second comparator.

[0051] The second end of the twentieth resistor is connected to the output of the second comparator;

[0052] The second terminal of the fourth diode is grounded;

[0053] The inverting input of the second comparator is connected to the output of the adjustment circuit.

[0054] The regulating circuit includes the twenty-first resistor and the twenty-second resistor;

[0055] Among them, the first end of the twenty-first resistor is connected to the first end of the sixteenth resistor, the second end of the fifteenth resistor, and the first end of the second capacitor; the second end of the twenty-first resistor is connected to the first end of the twenty-second resistor, the inverting input of the first comparator, and the inverting input of the second comparator.

[0056] The second terminal of the twenty-second resistor is grounded.

[0057] Preferably, it also includes a twenty-third resistor;

[0058] The first end of the twenty-third resistor is connected to the non-inverting output terminal of the sensor and the first end of the first resistor, while the second end of the twenty-third resistor is connected to the inverting output terminal of the sensor and the first end of the third resistor.

[0059] To address the aforementioned issues, this application also provides a threshold-adaptive frequency measurement device, including the aforementioned threshold-adaptive frequency measurement circuit.

[0060] This application provides a threshold-adaptive frequency measurement circuit, comprising: a filter circuit, a charging circuit, and a hysteresis comparator module. The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, and is used to charge the charging circuit. The hysteresis comparator module is connected to the charging circuit, the filter circuit, and an FPGA, and is used to adjust the comparison threshold according to the voltage of the charging circuit. The frequency measurement method of this application can adaptively adjust the comparison voltage threshold based on the signal amplitude, filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine. Attached Figure Description

[0061] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a schematic diagram of the equal-precision frequency measurement principle of the prior art in this application;

[0063] Figure 2 The above diagram shows the signal waveforms before and after shaping, as per the prior art of this application.

[0064] Figure 3 A block diagram of the threshold adaptive frequency measurement circuit provided in the embodiments of this application;

[0065] Figure 4 A block diagram of the overall threshold adaptive frequency measurement circuit provided in the embodiments of this application;

[0066] Figure 5A circuit diagram of a threshold-adaptive frequency measurement circuit provided in an embodiment of this application;

[0067] Figure 6 The output waveforms of each stage of the circuit provided in the embodiments of this application. Detailed Implementation

[0068] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0069] The core of this application is to provide a threshold-adaptive frequency measurement circuit and device. It can adaptively adjust the comparison voltage threshold based on the signal amplitude, filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine.

[0070] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] like Figure 1 , 2 As shown, converting irregular or superimposed interference square waves and sine waves output from on-site speed sensors into standard square wave signals and performing equal-precision frequency measurement via an FPGA is a widely used method in various frequency measurement fields. Equal-precision frequency measurement technology measures the frequency of the measured signal using a reference clock signal. Its accuracy is independent of the measured signal frequency, depending only on the accuracy and magnitude of the reference clock signal. Its principle is as follows: Figure 1 As shown. Two counters were used during the measurement process, one of which monitored the frequency pulse f. x One counter counts the frequency pulses, while the other counts the reference clock pulse f0. However, the counter does not start counting immediately; it waits until the rising edge of the measured frequency signal appears at time t2. Similarly, when the preset frequency measurement period ends at time t2 and the counting gate closes, the counter does not stop counting immediately; it waits until another rising edge of the measured frequency signal appears at time t3. Therefore, there is...

[0072] Under normal circumstances, the error in high-precision frequency measurement is very small, with an error of only ±1 reference clock pulse in the counting of the reference signal. However, most field applications involve long-distance transmission between the speed sensor and the cable, and the frequency measurement module channel is designed with a fixed comparison threshold. As the rotational speed increases, the pulse signal amplitude increases, and the amplitude of the interference signal also increases. Assuming that Ui increases with the pulse signal amplitude, the ringing amplitude exceeds the fixed comparison threshold of the speed measurement channel, after being processed into a square wave by the shaping circuit, the measured frequency pulse f... x The count N1 will increase, which will affect the frequency measurement accuracy.

[0073] Among them, U H To compare the upper limit of the threshold, U L To compare the lower limit of the threshold, u i For the acquired signal, U O The voltage of the shaped waveform.

[0074] Figure 3 A block diagram of the threshold adaptive frequency measurement circuit provided in the embodiments of this application is shown below. Figure 3 As shown, a threshold-adaptive frequency measurement circuit includes: a filter circuit, a charging circuit, and a hysteresis comparator module.

[0075] The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, respectively, and is used to charge the charging circuit.

[0076] The hysteresis comparator module is connected to the charging circuit, the hysteresis comparator module and the FPGA respectively, and is used to adjust the comparison threshold according to the voltage of the charging circuit.

[0077] In a specific embodiment, such as Figure 3 As shown, the sensor is 1, the filter circuit is 2, the charging circuit is 3, the hysteresis comparator module is 4, and the FPGA is 5.

[0078] The filter circuit 2 is connected to the sensor 1, the charging circuit 3, and the hysteresis comparator module 4, respectively, and is used to charge the charging circuit 3. The hysteresis comparator module 4 is connected to the charging circuit 3, the filter circuit 2, and the FPGA 5, respectively, and is used to adjust the comparison threshold according to the voltage of the charging circuit 3 and the voltage of the filter circuit 2.

[0079] It should be noted that the model of the sensor and the model of the FPGA are not limited in this application and can be set by the user according to their needs.

[0080] It should be noted that the specific circuit design of the filter circuit, charging circuit, and hysteresis comparator module is not limited in this application, and can be set by the user according to their needs.

[0081] This application provides a threshold-adaptive frequency measurement circuit, comprising: a filter circuit, a charging circuit, and a hysteresis comparator module. The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, and is used to charge the charging circuit. The hysteresis comparator module is connected to the charging circuit, the filter circuit, and an FPGA, and is used to adjust the comparison threshold according to the voltage of the charging circuit. The frequency measurement method of this application can adaptively adjust the comparison voltage threshold based on the signal amplitude, filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine.

[0082] Based on the above embodiments, as a preferred embodiment, the filter circuit includes a positive protection circuit, a negative protection circuit, a first subtractor circuit, a first-order inertial filter circuit, a second subtractor circuit, and a third subtractor circuit, used to charge the charging circuit.

[0083] The first input terminal of the first subtractor circuit is connected to the non-inverting output terminal of the sensor, the second input terminal of the first subtractor circuit is connected to the inverting output terminal of the sensor, and the output terminal of the first subtractor circuit is connected to the input terminal of the first-order inertial filter circuit, the first input terminal of the second subtractor circuit, and the first input terminal of the third subtractor circuit.

[0084] The positive protection circuit is connected to the non-inverting output terminal of the sensor and the first input terminal of the first subtractor circuit;

[0085] The negative protection circuit is connected to the inverted output terminal of the sensor and the second input terminal of the first subtractor circuit;

[0086] The output of the first-order inertial filter circuit is connected to the second input of the second subtractor circuit and the second input of the third subtractor circuit.

[0087] The output of the second subtractor circuit is connected to the first input of the charging circuit and the first input of the hysteresis comparator module.

[0088] The output of the third subtractor circuit is connected to the second input of the charging circuit and the first input of the hysteresis comparator module.

[0089] In a specific embodiment, such as Figure 4 As shown, there are positive protection circuit 6, negative protection circuit 7, first subtractor circuit 8, first-order inertial filter circuit 9, second subtractor circuit 10, and third subtractor circuit 11.

[0090] In this circuit, the first input terminal of the first subtractor circuit 8 is connected to the non-inverting output terminal of the sensor 1, the second input terminal of the first subtractor circuit 8 is connected to the inverting output terminal of the sensor 1, and the output terminal of the first subtractor circuit 8 is connected to the input terminal of the first-order inertial filter circuit 9, the first input terminal of the second subtractor circuit 10, and the first input terminal of the third subtractor circuit 11; the positive electrode protection circuit 6 is connected to the non-inverting output terminal of the sensor 1 and the first input terminal of the first subtractor circuit 8; the negative electrode protection circuit 7 is connected to the inverting output terminal of the sensor 1 and the second input terminal of the first subtractor circuit 8; the output terminal of the first-order inertial filter circuit 9 is connected to the second input terminal of the second subtractor circuit 10 and the second input terminal of the third subtractor circuit 11; the output terminal of the second subtractor circuit 10 is connected to the first input terminal of the charging circuit 3 and the first input terminal of the hysteresis comparator module 4; and the output terminal of the third subtractor circuit 11 is connected to the second input terminal of the charging circuit 3 and the first input terminal of the hysteresis comparator module 4.

[0091] Among them, the positive protection circuit 6 and the negative protection circuit 7 are used to clamp the voltage and prevent the voltage from exceeding the range of subsequent circuit devices. The first subtractor circuit 8 is used to convert the speed signal into a single-ended output for easy conversion in the subsequent stage. The first-order inertial filter circuit 9 has a certain suppression effect on high-frequency signals, making it easier for subsequent circuit devices to obtain signals with higher amplitude. The second subtractor circuit 10 and the third subtractor circuit 11 are used to charge the charging circuit.

[0092] The positive and negative protection circuits can be suppression diodes or other devices. This application does not limit the types of devices and allows users to configure them according to their needs.

[0093] It should be noted that this application does not limit the specific circuit components in the positive protection circuit, negative protection circuit, first subtractor circuit, first-order inertial filter circuit, second subtractor circuit, and third subtractor circuit. These components can be set according to the user's needs, and this application does not limit them.

[0094] This embodiment uses a positive protection circuit, a negative protection circuit, a first subtractor circuit, a first-order inertial filter circuit, a second subtractor circuit, and a third subtractor circuit to charge the charging circuit so that subsequent circuits can adjust the comparison threshold according to the charging circuit.

[0095] Based on the above embodiments, as a preferred embodiment, the hysteresis comparator module includes: a first hysteresis comparator circuit, a second hysteresis comparator circuit, and an adjustment circuit for adjusting the comparison threshold value according to the voltage of the charging circuit.

[0096] Wherein, the first input terminal of the first hysteresis comparator circuit is connected to the output terminal of the second subtractor circuit, the second input terminal of the first hysteresis comparator circuit is connected to the output terminal of the adjustment circuit, and the output terminal of the first hysteresis comparator circuit is connected to the FPGA.

[0097] The first input of the second hysteresis comparator circuit is connected to the output of the third subtractor circuit, the second input of the second hysteresis comparator circuit is connected to the output of the adjustment circuit, and the output of the second hysteresis comparator circuit is connected to the FPGA.

[0098] The input terminal of the regulating circuit is connected to the output terminal of the charging circuit.

[0099] In a specific embodiment, such as Figure 4 As shown, there is a first hysteresis comparator circuit 12, a second hysteresis comparator circuit 13, and an adjustment circuit 14.

[0100] Specifically, the first input terminal of the first hysteresis comparator circuit 12 is connected to the output terminal of the second subtractor circuit 10, the second input terminal of the first hysteresis comparator circuit 12 is connected to the output terminal of the adjustment circuit 14, and the output terminal of the first hysteresis comparator circuit 12 is connected to the FPGA 5; the first input terminal of the second hysteresis comparator circuit 12 is connected to the output terminal of the third subtractor circuit 11, the second input terminal of the second hysteresis comparator circuit 12 is connected to the output terminal of the adjustment circuit 14, and the output terminal of the second hysteresis comparator circuit 13 is connected to the FPGA 5; the input terminal of the adjustment circuit 14 is connected to the output terminal of the charging circuit 3.

[0101] The first hysteresis comparator circuit 12, the second hysteresis comparator circuit 13, and the adjustment circuit 14 are used to adjust the comparison threshold according to the voltage of the charging circuit 3.

[0102] It should be noted that this application does not limit the first hysteresis comparator circuit 12 and the second hysteresis comparator circuit 13. The specific circuit components in the adjustment circuit 14 can be set by the user according to their needs, and this application does not limit them.

[0103] In this embodiment, a first hysteresis comparator circuit, a second hysteresis comparator circuit, and an adjustment circuit are used to adjust the comparison threshold in order to reduce interference from the error signal.

[0104] Based on the above embodiments, as a preferred embodiment, the first subtractor circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor;

[0105] Wherein, the first end of the first resistor is connected to the non-inverting input terminal of the sensor, and the second end of the first resistor is connected to the positive protection circuit, the inverting input terminal of the first operational amplifier, and the first end of the second resistor;

[0106] The second end of the second resistor is connected to the output of the first operational amplifier;

[0107] The first end of the third resistor is connected to the inverting input terminal of the sensor, and the second end of the third resistor is connected to the negative protection circuit, the non-inverting input terminal of the first operational amplifier, and the first end of the fourth resistor.

[0108] The second terminal of the fourth resistor is grounded.

[0109] In a specific embodiment, such as Figure 5 As shown, the first operational amplifier U1, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are all present.

[0110] In this circuit, the first end of the first resistor R1 is connected to the non-inverting input terminal of the sensor 1, the second end of the first resistor R1 is connected to the positive protection circuit 6, the inverting input terminal of the first operational amplifier U1, and the first end of the second resistor R2; the second end of the second resistor R2 is connected to the output terminal of the first operational amplifier U1; the first end of the third resistor R3 is connected to the inverting input terminal of the sensor 1, the second end of the third resistor R3 is connected to the negative protection circuit 7, the non-inverting input terminal of the first operational amplifier U1, and the first end of the fourth resistor R4; the second end of the fourth resistor R4 is grounded.

[0111] It should be noted that the resistance value is not limited in this application and can be set according to the user's needs. Similarly, the operational amplifier model is not limited in this application and can be set according to the user's needs.

[0112] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0113] Based on the above embodiments, as a preferred embodiment, the first-order inertial filter circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor, and a first capacitor;

[0114] The first end of the fifth resistor is connected to the output terminal of the first operational amplifier and the second end of the second resistor, and the second end of the fifth resistor is connected to the first end of the first capacitor and the non-inverting input terminal of the second operational amplifier.

[0115] The second terminal of the first capacitor is grounded;

[0116] The first end of the sixth resistor is connected to the inverting input of the second operational amplifier, and the second end of the sixth resistor is connected to the output of the second operational amplifier.

[0117] In a specific embodiment, such as Figure 5 As shown, the second operational amplifier U2, the fifth resistor R5, the sixth resistor R6, and the first capacitor C1 are included.

[0118] Among them, the first end of the fifth resistor R5 is connected to the output terminal of the first operational amplifier U1 and the second end of the second resistor R2. The second end of the fifth resistor R5 is connected to the first end of the first capacitor C1 and the non-inverting input terminal of the second operational amplifier U2. The second end of the first capacitor C1 is grounded. The first end of the sixth resistor R6 is connected to the inverting input terminal of the second operational amplifier U2, and the second end of the sixth resistor R6 is connected to the output terminal of the second operational amplifier U2.

[0119] It should be noted that the resistance value is not limited in this application and can be set according to the user's needs. Similarly, the operational amplifier model is not limited in this application and can be set according to the user's needs.

[0120] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0121] Based on the above embodiments, as a preferred embodiment, the second subtractor circuit includes: a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor.

[0122] The first end of the seventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor; the second end of the seventh resistor is connected to the first end of the eighth resistor and the inverting input terminal of the third operational amplifier.

[0123] The second terminal of the eighth resistor is connected to the output terminal of the third operational amplifier;

[0124] The first end of the ninth resistor is connected to the second end of the sixth resistor and the output terminal of the second operational amplifier; the second end of the ninth resistor is connected to the first end of the tenth resistor and the non-inverting input terminal of the third operational amplifier.

[0125] The second terminal of the tenth resistor is grounded;

[0126] The third subtractor circuit includes: a fourth operational amplifier, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a fourteenth resistor.

[0127] Among them, the first end of the eleventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor; the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the non-inverting input terminal of the fourth operational amplifier.

[0128] The second terminal of the twelfth resistor is grounded;

[0129] The first end of the thirteenth resistor is connected to the second end of the sixth resistor, the output of the second operational amplifier, and the first end of the ninth resistor. The second end of the thirteenth resistor is connected to the first end of the fourteenth resistor and the inverting input of the fourth operational amplifier.

[0130] In a specific embodiment, such as Figure 5 As shown, the third operational amplifier U3, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, the fourth operational amplifier U4, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, and the fourteenth resistor R14 are all connected.

[0131] Among them, the first end of the seventh resistor R7 is connected to the second end of the second resistor R2, the output terminal of the first operational amplifier U1, and the first end of the fifth resistor R5; the second end of the seventh resistor R7 is connected to the first end of the eighth resistor R8 and the inverting input terminal of the third operational amplifier U3; the second end of the eighth resistor R8 is connected to the output terminal of the third operational amplifier U3; the first end of the ninth resistor R9 is connected to the second end of the sixth resistor R6 and the output terminal of the second operational amplifier U2; the second end of the ninth resistor R9 is connected to the first end of the tenth resistor R10 and the non-inverting input terminal of the third operational amplifier U3; the second end of the tenth resistor R10 is grounded.

[0132] Among them, the first end of the eleventh resistor R11 is connected to the second end of the second resistor R2, the output terminal of the first operational amplifier U1, and the first end of the fifth resistor R5; the second end of the eleventh resistor R11 is connected to the first end of the twelfth resistor R12 and the non-inverting input terminal of the fourth operational amplifier U4; the second end of the twelfth resistor R12 is grounded; the first end of the thirteenth resistor R13 is connected to the second end of the sixth resistor R6, the output terminal of the second operational amplifier U2, and the first end of the ninth resistor R9; the second end of the thirteenth resistor R13 is connected to the first end of the fourteenth resistor R14 and the inverting input terminal of the fourth operational amplifier U4.

[0133] It should be noted that the resistance value is not limited in this application and can be set according to the user's needs. Similarly, the operational amplifier model is not limited in this application and can be set according to the user's needs.

[0134] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0135] Based on the above embodiments, as a preferred embodiment, the charging circuit includes a first diode, a second diode, a fifteenth resistor, a sixteenth resistor, and a second capacitor;

[0136] The first end of the first diode is connected to the second end of the fourteenth resistor and the output end of the fourth operational amplifier, and the second end of the first diode is connected to the first end of the fifteenth resistor.

[0137] The second end of the fifteenth resistor is connected to the first end of the sixteenth resistor and the first end of the second capacitor;

[0138] The second terminal of the sixteenth resistor is connected to the first terminal of the second diode;

[0139] The second terminal of the second diode is connected to the second terminal of the eighth resistor and the output terminal of the third operational amplifier;

[0140] The second terminal of the second capacitor is grounded.

[0141] In a specific embodiment, such as Figure 5 As shown, there is a first diode D1, a second diode D2, a fifteenth resistor R15, a sixteenth resistor R16, and a second capacitor C2.

[0142] Specifically, the first terminal of the first diode D1 is connected to the second terminal of the fourteenth resistor R14 and the output terminal of the fourth operational amplifier U4; the second terminal of the first diode D1 is connected to the first terminal of the fifteenth resistor R15; the second terminal of the fifteenth resistor R15 is connected to the first terminal of the sixteenth resistor R16 and the first terminal of the second capacitor C2; the second terminal of the sixteenth resistor R16 is connected to the first terminal of the second diode D2; the second terminal of the second diode D2 is connected to the second terminal of the eighth resistor R8 and the output terminal of the third operational amplifier U3; and the second terminal of the second capacitor C2 is grounded.

[0143] It should be noted that the resistance value and capacitance value are not limited in this application and can be set according to the user's needs. Similarly, the diode model is not limited in this application and can be set according to the user's needs.

[0144] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0145] Based on the above embodiments, as a preferred embodiment, the first hysteresis comparator circuit includes: a first comparator, a seventeenth resistor, an eighteenth resistor, and a third diode;

[0146] The first end of the seventeenth resistor is connected to the second end of the second diode, the second end of the eighth resistor, and the output terminal of the third operational amplifier. The second end of the seventeenth resistor is connected to the first end of the eighteenth resistor, the first end of the third diode, and the non-inverting input terminal of the first comparator.

[0147] The second end of the eighteenth resistor is connected to the output of the first comparator;

[0148] The second terminal of the third diode is grounded;

[0149] The inverting input of the first comparator is connected to the output of the adjustment circuit.

[0150] The second hysteresis comparator circuit includes: a second comparator, a nineteenth resistor, a twentieth resistor, and a fourth diode;

[0151] Among them, the first end of the nineteenth resistor is connected to the second end of the fourteenth resistor and the output terminal of the fourth operational amplifier, and the second end of the nineteenth resistor is connected to the first end of the fourth diode, the first end of the twentieth resistor, and the non-inverting input terminal of the second comparator.

[0152] The second end of the twentieth resistor is connected to the output of the second comparator;

[0153] The second terminal of the fourth diode is grounded;

[0154] The inverting input of the second comparator is connected to the output of the adjustment circuit.

[0155] The regulating circuit includes the twenty-first resistor and the twenty-second resistor;

[0156] Among them, the first end of the twenty-first resistor is connected to the first end of the sixteenth resistor, the second end of the fifteenth resistor, and the first end of the second capacitor; the second end of the twenty-first resistor is connected to the first end of the twenty-second resistor, the inverting input of the first comparator, and the inverting input of the second comparator.

[0157] The second terminal of the twenty-second resistor is grounded.

[0158] In a specific embodiment, such as Figure 5 As shown, the components include the first comparator U5, the seventeenth resistor R17, the eighteenth resistor R18, the third diode D3, the second comparator U6, the nineteenth resistor R19, the twentieth resistor R20, the fourth diode D4, the twenty-first resistor R21, and the twenty-second resistor R22.

[0159] Specifically, the first end of the seventeenth resistor R17 is connected to the second end of the second diode D2, the second end of the eighth resistor R8, and the output of the third operational amplifier U3; the second end of the seventeenth resistor R17 is connected to the first end of the eighteenth resistor R18, the first end of the third diode D3, and the non-inverting input of the first comparator U5; the second end of the eighteenth resistor R18 is connected to the output of the first comparator U5; the second end of the third diode D3 is grounded; and the inverting input of the first comparator U5 is connected to the output of the adjustment circuit.

[0160] Specifically, the first end of the nineteenth resistor R19 is connected to the second end of the fourteenth resistor R14 and the output of the fourth operational amplifier U4; the second end of the nineteenth resistor R19 is connected to the first end of the fourth diode D4, the first end of the twentieth resistor R20, and the non-inverting input of the second comparator U6; the second end of the twentieth resistor R20 is connected to the output of the second comparator U6; the second end of the fourth diode D4 is grounded; and the inverting input of the second comparator U6 is connected to the output of the adjustment circuit.

[0161] Among them, the first end of the twenty-first resistor R21 is connected to the first end of the sixteenth resistor R16, the second end of the fifteenth resistor R15, and the first end of the second capacitor C2; the second end of the twenty-first resistor R21 is connected to the first end of the twenty-second resistor R22, the inverting input of the first comparator U5, and the inverting input of the second comparator U6; the second end of the twenty-second resistor R22 is grounded.

[0162] It should be noted that the resistance value and capacitance size are not limited in this application, and the resistance value can be set according to the user's needs. Similarly, the comparator model is not limited in this application, and can be set according to the user's needs.

[0163] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0164] Based on the above embodiments, as a preferred embodiment, the circuit further includes a twenty-third resistor;

[0165] The first end of the twenty-third resistor is connected to the non-inverting output terminal of the sensor and the first end of the first resistor, while the second end of the twenty-third resistor is connected to the inverting output terminal of the sensor and the first end of the third resistor.

[0166] In a specific embodiment, such as Figure 5 As shown, the twenty-third resistor is R23.

[0167] Among them, the first end of the twenty-third resistor R23 is connected to the non-inverting output terminal of sensor 1 and the first end of the first resistor R1, and the second end of the twenty-third resistor R23 is connected to the inverting output terminal of sensor 1 and the first end of the third resistor R3.

[0168] It should be noted that the resistance value is not limited in this application, and the user can set the resistance value according to their needs.

[0169] The embodiments described in this application are only one possible solution, but are not limited to this one implementation method. Users can customize the implementation according to their needs.

[0170] In summary, the above embodiments mostly use magnetoresistive speed sensors in the field. Their characteristic is that the amplitude of the output signal increases with the increase of the sampling frequency. R23 is used for frequency signal sampling and is generally a common resistor of about 10K. U1 is a differential operational amplifier with high common-mode rejection ratio. R1 to R4 are the internal resistor network of the differential operational amplifier. The purpose of the differential operational amplifier is to convert the floating ground speed signal into a single-ended output for easy conversion in subsequent stages. U2, R5, R6, and C1 form a first-order inertial filter circuit, which aims to suppress high-frequency signals to facilitate the subtractor composed of U3 and U4 to obtain a higher amplitude signal. U3 and R7-R10 form a subtraction circuit that charges C2 by subtracting the signal from the first-order inertial filter. Similarly, U4 and R11-R14 form a subtraction circuit that charges C2 by subtracting the signal from the first-order inertial filter. Since the signals at U3 and U4 are 180° out of phase, C2 is charged throughout the entire cycle of the input signal. This makes the voltage on C2 relatively stable and prevents large fluctuations, allowing it to serve as a reference voltage for the subsequent hysteresis comparator. U5, R17, and R18 form a hysteresis comparator. When the input signal amplitude is greater than the comparison voltage on R18, the comparator outputs a high level; otherwise, it outputs a low level. U6, R19, and R20 form a hysteresis comparator. When the input signal amplitude is greater than the comparison voltage on R20, the comparator outputs a high level; otherwise, it outputs a low level. The voltage on R22 changes with the amplitude of Ui; as the amplitude of Ui increases, the voltage on R22 increases proportionally, and vice versa. The output signals of U6 and U7 simultaneously enter the FPGA. An SR filter is set up inside the FPGA to process the signals, and then the current frequency is calculated using an equal-precision frequency measurement method. For example... Figure 5 , 6 As shown, Ui is the acquired signal, U11 is the output waveform of U1, U12 is the output waveform of U2, U13 is the output waveform of U3, U14 is the output waveform of U4, U15 is the output waveform of nodes R16 and C2, U16 is the output waveform of U5, and U17 is the output waveform of U6. FI+ and FI- are the non-inverting and inverting output terminals of the sensor, respectively. FI1, FI2, S, Q, and R are all FPGA connection points. Q1 is the positive protection circuit, and Q2 is the negative protection circuit.

[0171] To address the aforementioned issues, this application also provides a threshold-adaptive frequency measurement device, including the aforementioned threshold-adaptive frequency measurement circuit.

[0172] Since the embodiments of the device part correspond to the embodiments of the circuit part, please refer to the description of the embodiments of the circuit part for the embodiments of the device part, and they will not be repeated here.

[0173] This application provides a threshold-adaptive frequency measurement device, comprising a threshold-adaptive frequency measurement circuit. This circuit includes a filter circuit, a charging circuit, and a hysteresis comparator module. The filter circuit is connected to a sensor, the charging circuit, and the hysteresis comparator module, and is used to charge the charging circuit. The hysteresis comparator module is connected to the charging circuit, the filter circuit, and an FPGA, and is used to adjust the comparison threshold according to the voltage of the charging circuit. This embodiment of the application adjusts the comparison threshold according to the voltage, which can filter out interference signals, increase the stability of frequency measurement, and ensure the normal operation of the steam turbine.

[0174] The threshold-adaptive frequency measurement circuit and apparatus provided in this application have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0175] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A threshold-adaptive frequency measurement circuit, characterized in that, include: Filtering circuit, charging circuit, hysteresis comparator module; The filter circuit is connected to the sensor, the charging circuit, and the hysteresis comparator module, respectively, and is used to charge the charging circuit. The hysteresis comparator module is connected to the charging circuit, the filtering circuit and the FPGA respectively, and is used to adjust the comparison threshold according to the voltage of the charging circuit. The filtering circuit includes a positive protection circuit, a negative protection circuit, a first subtractor circuit, a first-order inertial filter circuit, a second subtractor circuit, and a third subtractor circuit, used to charge the charging circuit. Wherein, the first input terminal of the first subtractor circuit is connected to the non-inverting output terminal of the sensor, the second input terminal of the first subtractor circuit is connected to the inverting output terminal of the sensor, and the output terminal of the first subtractor circuit is connected to the input terminal of the first-order inertial filter circuit, the first input terminal of the second subtractor circuit, and the first input terminal of the third subtractor circuit. The positive protection circuit is connected to the same-direction output terminal of the sensor and the first input terminal of the first subtractor circuit; The negative electrode protection circuit is connected to the reverse output terminal of the sensor and the second input terminal of the first subtractor circuit; The output terminal of the first-order inertial filter circuit is connected to the second input terminal of the second subtractor circuit and the second input terminal of the third subtractor circuit; The output of the second subtractor circuit is connected to the first input of the charging circuit and the first input of the hysteresis comparator module. The output of the third subtractor circuit is connected to the second input of the charging circuit and the first input of the hysteresis comparator module.

2. The threshold-adaptive frequency measurement circuit according to claim 1, characterized in that, The hysteresis comparator module includes: a first hysteresis comparator circuit, a second hysteresis comparator circuit, and an adjustment circuit for adjusting the comparison threshold value according to the voltage of the charging circuit. Wherein, the first input terminal of the first hysteresis comparator circuit is connected to the output terminal of the second subtractor circuit, the second input terminal of the first hysteresis comparator circuit is connected to the output terminal of the adjustment circuit, and the output terminal of the first hysteresis comparator circuit is connected to the FPGA; The first input terminal of the second hysteresis comparator circuit is connected to the output terminal of the third subtractor circuit, the second input terminal of the second hysteresis comparator circuit is connected to the output terminal of the adjustment circuit, and the output terminal of the second hysteresis comparator circuit is connected to the FPGA. The input terminal of the regulating circuit is connected to the output terminal of the charging circuit.

3. The threshold-adaptive frequency measurement circuit according to claim 2, characterized in that, The first subtractor circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor; Wherein, the first end of the first resistor is connected to the non-inverting input terminal of the sensor, and the second end of the first resistor is connected to the positive protection circuit, the inverting input terminal of the first operational amplifier, and the first end of the second resistor; The second end of the second resistor is connected to the output terminal of the first operational amplifier; The first end of the third resistor is connected to the inverting input terminal of the sensor, and the second end of the third resistor is connected to the negative protection circuit, the non-inverting input terminal of the first operational amplifier, and the first end of the fourth resistor. The second terminal of the fourth resistor is grounded.

4. The threshold-adaptive frequency measurement circuit according to claim 3, characterized in that, The first-order inertial filter circuit includes: a second operational amplifier, a fifth resistor, a sixth resistor, and a first capacitor; Wherein, the first end of the fifth resistor is connected to the output terminal of the first operational amplifier and the second end of the second resistor, and the second end of the fifth resistor is connected to the first end of the first capacitor and the non-inverting input terminal of the second operational amplifier; The second terminal of the first capacitor is grounded; The first end of the sixth resistor is connected to the inverting input of the second operational amplifier, and the second end of the sixth resistor is connected to the output of the second operational amplifier.

5. The threshold-adaptive frequency measurement circuit according to claim 4, characterized in that, The second subtractor circuit includes: a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, and a tenth resistor. Wherein, the first end of the seventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor, and the second end of the seventh resistor is connected to the first end of the eighth resistor and the inverting input terminal of the third operational amplifier; The second end of the eighth resistor is connected to the output terminal of the third operational amplifier; The first end of the ninth resistor is connected to the second end of the sixth resistor and the output terminal of the second operational amplifier, and the second end of the ninth resistor is connected to the first end of the tenth resistor and the non-inverting input terminal of the third operational amplifier; The second terminal of the tenth resistor is grounded; The third subtractor circuit includes: a fourth operational amplifier, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a fourteenth resistor. Wherein, the first end of the eleventh resistor is connected to the second end of the second resistor, the output terminal of the first operational amplifier, and the first end of the fifth resistor, and the second end of the eleventh resistor is connected to the first end of the twelfth resistor and the non-inverting input terminal of the fourth operational amplifier; The second terminal of the twelfth resistor is grounded; The first end of the thirteenth resistor is connected to the second end of the sixth resistor, the output terminal of the second operational amplifier, and the first end of the ninth resistor. The second end of the thirteenth resistor is connected to the first end of the fourteenth resistor and the inverting input terminal of the fourth operational amplifier.

6. The threshold-adaptive frequency measurement circuit according to claim 5, characterized in that, The charging circuit includes a first diode, a second diode, a fifteenth resistor, a sixteenth resistor, and a second capacitor; Wherein, the first end of the first diode is connected to the second end of the fourteenth resistor and the output end of the fourth operational amplifier, and the second end of the first diode is connected to the first end of the fifteenth resistor; The second end of the fifteenth resistor is connected to the first end of the sixteenth resistor and the first end of the second capacitor; The second end of the sixteenth resistor is connected to the first end of the second diode; The second terminal of the second diode is connected to the second terminal of the eighth resistor and the output terminal of the third operational amplifier; The second terminal of the second capacitor is grounded.

7. The threshold-adaptive frequency measurement circuit according to claim 6, characterized in that, The first hysteresis comparator circuit includes: a first comparator, a seventeenth resistor, an eighteenth resistor, and a third diode; Wherein, the first end of the seventeenth resistor is connected to the second end of the second diode, the second end of the eighth resistor, and the output terminal of the third operational amplifier; the second end of the seventeenth resistor is connected to the first end of the eighteenth resistor, the first end of the third diode, and the non-inverting input terminal of the first comparator. The second end of the eighteenth resistor is connected to the output of the first comparator; The second terminal of the third diode is grounded; The inverting input of the first comparator is connected to the output of the adjustment circuit; The second hysteresis comparator circuit includes: a second comparator, a nineteenth resistor, a twentieth resistor, and a fourth diode; Wherein, the first end of the nineteenth resistor is connected to the second end of the fourteenth resistor and the output terminal of the fourth operational amplifier, and the second end of the nineteenth resistor is connected to the first end of the fourth diode, the first end of the twentieth resistor and the non-inverting input terminal of the second comparator; The second end of the twentieth resistor is connected to the output of the second comparator; The second terminal of the fourth diode is grounded; The inverting input of the second comparator is connected to the output of the adjustment circuit; The regulating circuit includes a twenty-first resistor and a twenty-second resistor; Wherein, the first end of the 21st resistor is connected to the first end of the 16th resistor, the second end of the 15th resistor, and the first end of the second capacitor; the second end of the 21st resistor is connected to the first end of the 22nd resistor, the inverting input of the first comparator, and the inverting input of the second comparator. The second terminal of the twentieth resistor is grounded.

8. A threshold-adaptive frequency measurement circuit according to any one of claims 3-7, characterized in that, It also includes the twenty-third resistor; The first end of the 23rd resistor is connected to the non-inverting output terminal of the sensor and the first end of the first resistor, and the second end of the 23rd resistor is connected to the inverting output terminal of the sensor and the first end of the third resistor.

9. A threshold-adaptive frequency measurement device, characterized in that, Includes the threshold-adaptive frequency measurement circuit as described in any one of claims 1-8.

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