Vibrating wire signal conditioning circuit

Abstract

The utility model provides a vibrating wire signal conditioning circuit, which is powered by a single power supply and comprises a radio frequency filter circuit, a common-mode voltage circuit, a signal conditioning circuit, a sensor state detection circuit and a microcontroller, the radio frequency filter circuit and the common-mode voltage circuit are respectively connected with the signal conditioning circuit, the common-mode voltage circuit is used for conditioning bipolar signals from the radio frequency filter circuit into unipolar signals, and the signal conditioning circuit and the sensor state detection circuit are both connected with the microcontroller. And the sensor state detection circuit is connected with the radio frequency filter circuit. According to the application, when a single power supply is used for supplying power to the vibrating wire signal conditioning circuit, the signal chain works normally, the complexity, the cost and the size of the vibrating wire signal conditioning circuit can be reduced, and the power consumption of the circuit can be reduced.

Description

Technical Field

[0001] This utility model relates to the field of electronic information technology, and in particular to a vibrating string signal conditioning circuit. Background Technology

[0002] Vibrating wire acquisition equipment has a wide range of applications in engineering monitoring. It can be used for vibration monitoring of various buildings, bridges, tunnels, hydropower stations, wind farms and other large-scale projects.

[0003] Currently, most signal conditioning circuits inside vibrating wire acquisition devices use dual power supplies. The main disadvantages of dual power supply signal chains include the following:

[0004] Complexity: The design of a dual-supply signal chain is more complex than that of a single-supply signal chain because it requires managing two independent power supplies. This increases system complexity and can potentially increase development and maintenance costs; in addition, generating a negative power supply is generally inconvenient.

[0005] Power consumption: Due to the use of two independent power supplies, dual-supply signal chains typically consume more power than single-supply signal chains, which poses a challenge for battery-powered systems or applications requiring low power consumption.

[0006] Cost: Dual-supply signal chains require more components and materials, so they are generally more expensive than single-supply signal chains.

[0007] Space requirements: Due to the need for more components and materials, dual-power signal chains may require more physical space for installation. Summary of the Invention

[0008] Therefore, the purpose of this utility model is to provide a vibrating string signal conditioning circuit to overcome the shortcomings of the prior art.

[0009] To achieve the above objectives, this utility model provides a vibrating wire signal conditioning circuit. The vibrating wire signal conditioning circuit is powered by a single power supply and includes an RF filter circuit, a common-mode voltage circuit, a signal conditioning circuit, a sensor state detection circuit, and a microcontroller. The RF filter circuit and the common-mode voltage circuit are respectively connected to the signal conditioning circuit. The common-mode voltage circuit is used to condition the bipolar signal from the RF filter circuit into a unipolar signal. The signal conditioning circuit and the sensor state detection circuit are both connected to the microcontroller, and the sensor state detection circuit is connected to the RF filter circuit.

[0010] The vibrating string signal output by the sensor state detection circuit is sequentially transmitted to the microcontroller through the radio frequency filter circuit, the common mode voltage circuit, and the signal conditioning circuit.

[0011] The beneficial effects of this utility model are as follows: The vibrating string signal conditioning circuit is powered by a single power supply. Then, the radio frequency filter circuit and the common-mode voltage circuit are connected to the signal conditioning circuit respectively. Both the signal conditioning circuit and the sensor state detection circuit are connected to the microcontroller. The sensor state detection circuit is also connected to the radio frequency filter circuit. The vibrating string signal output by the sensor state detection circuit is sent to the radio frequency filter circuit. After processing by the radio frequency filter circuit, it flows to the common-mode voltage circuit. The bipolar signal received by the common-mode voltage circuit is conditioned into a unipolar signal. Then, the unipolar vibrating string signal flows sequentially to the signal conditioning circuit and the microcontroller. This achieves normal operation of the signal chain when the vibrating string signal conditioning circuit is powered by a single power supply. This differs from existing technologies and helps reduce the complexity, cost, and size of the vibrating string signal conditioning circuit, as well as its power consumption.

[0012] Preferably, the signal conditioning circuit is connected to the microcontroller via an analog-to-digital converter.

[0013] Preferably, the signal conditioning circuit includes a signal amplification circuit, a high-pass filter, and a low-pass filter, wherein the radio frequency filter circuit, the signal amplification circuit, the high-pass filter, the low-pass filter, the analog-to-digital converter, and the microcontroller are connected in sequence.

[0014] Preferably, the common-mode voltage circuit includes a first common-mode voltage sub-circuit connected to the signal amplification circuit and a second common-mode voltage sub-circuit connected to the high-pass filter.

[0015] Preferably, the signal amplification circuit is an instrumentation amplifier, which includes a gain resistor, and the instrumentation amplifier amplifies the signal by the gain resistor.

[0016] Preferably, the transition band attenuation rate of the high-pass filter is 40 dB / dec, the transition band attenuation rate of the low-pass filter is 80 dB / dec, and the input terminals of both the high-pass filter and the low-pass filter are powered by a single power supply.

[0017] Preferably, the low-pass filter is connected to the analog-to-digital converter via a first voltage follower, and the sensor state detection circuit is connected to the analog-to-digital converter via a second voltage follower.

[0018] Preferably, the voltage provided by the common-mode voltage circuit is half the voltage provided by the power supply rail of the single power supply.

[0019] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 A structural block diagram of the vibrating wire signal conditioning circuit provided in this embodiment of the utility model;

[0021] Figure 2 Circuit diagrams of the radio frequency filtering circuit and signal amplification circuit provided for embodiments of this utility model;

[0022] Figure 3 A circuit diagram of the sensor state detection circuit provided for an embodiment of this utility model;

[0023] Figure 4 Circuit diagram of the common-mode voltage circuit provided in the embodiments of this utility model;

[0024] Figure 5 Circuit diagram of a high-pass filter provided for an embodiment of this utility model;

[0025] Figure 6 A circuit diagram of a low-pass filter provided for an embodiment of this utility model;

[0026] Figure 7 A circuit diagram of an analog-to-digital converter provided for an embodiment of this utility model.

[0027] Explanation of key component symbols:

[0028] 10. RF filter short circuit; 20. Signal amplification circuit; 30. High-pass filter; 40. Low-pass filter circuit; 50. Analog-to-digital converter; 60. Microcontroller; 70. Sensor status detection circuit.

[0029] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation

[0030] To facilitate understanding of this utility model, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of this utility model are shown in the drawings. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this utility model will be more thorough and complete.

[0031] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Please see Figure 1 The vibrating wire signal conditioning circuit in this embodiment of the present invention includes an RF filter circuit, a common-mode voltage circuit, a signal conditioning circuit, a sensor state detection circuit 70, and a microcontroller 60.

[0034] Among them: the vibrating wire signal conditioning circuit is powered by a single power supply, the radio frequency filter circuit is connected to the signal conditioning circuit, the radio frequency filter circuit is connected to the sensor status detection circuit 70, the sensor status detection circuit 70 is used to detect the vibrating wire sensor and send the detected vibrating wire signal to the radio frequency filter circuit, the radio frequency filter circuit is used to filter out radio frequency common mode interference and radio frequency differential mode interference of the vibrating wire signal to reduce DC offset voltage;

[0035] Specifically, such as Figure 2 As shown, Figure 2 The left-hand section of the circuit is an RF filter circuit, which consists of two resistors (represented by the characters R12 and R21) and three capacitors (represented by the characters C2, C3, and C4). R12 and C2, and R21 and C4 form two single-pole common-mode filters. The signal limiting bandwidth of the single-pole common-mode filters is fcm = 1 / 2πRCc, Cc = C2 = C4, and R = R12 = R21. R12, R21, C2, C3, and C4 together form a differential-mode signal filter. The signal limiting bandwidth of the differential-mode signal filter is fdm = 1 / 2πR(2Cd + Cc), and Cd = C3. C1 and C6 are input coupling capacitors used to isolate the vibrating string excitation signal.

[0036] In this embodiment, the sensor state detection circuit 70 is used to determine whether the vibrating wire sensor is open-circuited or short-circuited by controlling the application of a constant voltage to the vibrating wire sensor and then sampling the intermediate voltage of the current circuit.

[0037] It should be noted that, as Figure 3 The diagram shown is a circuit diagram of the sensor state detection circuit 70. Figure 3 In the circuit, four resistors (represented by the characters R5, R6, R7, and R8) and an optocoupler relay (represented by the character U2) form the input part of the sensor state detection circuit 70. A constant voltage (represented by the character AVCC) is connected to the circuit via a current-limiting resistor (represented by the character R9). Figure 2The resistors R14 and R19 in the circuit are used to determine the short-circuit and open-circuit states of the sensor circuit. For example, when the two wires of the sensor are short-circuited, R14 and R19 are short-circuited, and Vscm is close to 0V. When the two wires of the sensor are open-circuited, the voltage value of Vscm is determined by the voltage divider of R9, R14, and R19. By judging the difference in the voltage value of Vscm, the state of the circuit can be determined. When not working, Vscm_EN is high level, and the high-impedance open circuit at the output of U2 does not affect the signal chain. When it is necessary to judge the sensor circuit, Vscm_EN is low level, U2 is driven, and the DC power supply circuit is connected to the sensor circuit.

[0038] In this embodiment, the common-mode voltage circuit is connected to the signal conditioning circuit, which is in turn connected to the microcontroller 60. The signal conditioning circuit includes a signal amplification circuit 20, a high-pass filter 30, and a low-pass filter connected in sequence. The common-mode voltage circuit includes a first common-mode voltage sub-circuit connected to the signal amplification circuit 20 and a second common-mode voltage sub-circuit connected to the high-pass filter 30. The radio frequency filter circuit is connected to the signal amplification circuit 20 through the first common-mode voltage sub-circuit, and the second common-mode voltage sub-circuit is connected to the input terminal of the high-pass filter 30. The voltages provided by the first and second common-mode voltage sub-circuits are both half the voltage provided by the power supply rail of the single power supply. The circuit structures of the first and second common-mode voltage sub-circuits are the same.

[0039] It should be noted that, as Figure 4 The diagram shown is a circuit diagram of the first common-mode voltage sub-circuit or the second common-mode voltage sub-circuit. The principle of the first common-mode voltage sub-circuit or the second common-mode voltage sub-circuit generating common-mode voltage is as follows: the value of VCM is selected as 1 / 2 of the power rail, R39 = R40, U3C forms a voltage follower to improve the output driving capability of VCM, and R41 and C35 form a low-pass filter to improve the VCM signal.

[0040] It should be noted that both the first and second common-mode voltage sub-circuits are used to condition the bipolar signal into a unipolar signal; the signal amplification circuit 20 is used to amplify the weak vibrating string signal to a suitable amplitude to improve the signal-to-noise ratio and facilitate subsequent circuit processing; the high-pass filter 30 is used to filter out interference in the low-frequency part of the vibrating string signal bandwidth, which generally includes power frequency and harmonic interference, as well as other low-frequency interference components; the low-pass filter is used to filter out interference and noise in the high-frequency part outside the vibrating string signal bandwidth.

[0041] In this embodiment, if Figure 2The two resistors in the middle, represented by the characters R16 and R20, mainly function to superimpose a common-mode voltage (represented by the character VCM) onto the input bipolar differential vibrating string signal. This common-mode voltage is provided by the first common-mode voltage sub-circuit. For example, if the mathematical model of the original vibrating string signal is f(x) = Asin(x), after superimposing the common-mode voltage, the bipolar differential signal becomes a unipolar differential signal g(x) = Asin(x) + VCM. For example, if the range of f(x) is -2.5V to 2.5V and the common-mode voltage VCM is 2.5V, then the range of g(x) becomes a unipolar signal from 0V to 5V. This provides the basis for the vibrating string signal conditioning circuit to achieve single power supply.

[0042] In this embodiment, the signal amplification circuit 20 is an instrumentation amplifier, which includes a gain resistor. The instrumentation amplifier amplifies the signal by means of the gain resistor. Since a single-supply signal chain is used, the instrumentation amplifier is a model that supports single-supply mode. In addition, the original input bipolar differential vibrating string signal, i.e., the vibrating string signal, is processed by the radio frequency filter circuit and then needs to pass through the first common-mode voltage sub-circuit before being sent to the signal amplification circuit 20.

[0043] It should be noted that if Figure 2 The right-hand side circuit is the signal amplifier circuit 20, which is represented by the character U4 as an instrumentation amplifier. Since a single-supply signal chain is used, the reference voltage of the instrumentation amplifier also needs to be set to the common-mode voltage. The gain circuit is represented by the character R15, and the appropriate gain can be selected according to the strength of the vibrating string signal.

[0044] In this embodiment, the transition band attenuation rate of the high-pass filter 30 is 40 dB / dec, and the transition band attenuation rate of the low-pass filter is 80 dB / dec. The input terminals of both the high-pass filter 30 and the low-pass filter are powered by a single power supply.

[0045] It should be noted that if Figure 5 The diagram shown is a circuit diagram of the high-pass filter 30. Figure 4 In the design, the high-pass filter 30 is a two-order active high-pass filter with a Sallen-Key circuit topology. The filter response parameters are designed according to Butterworth parameters. The VCM provides a common-mode voltage to the signal through resistor R32, allowing it to operate in single-supply mode. The operational amplifier of the high-pass filter 30 needs to be a single-supply rail-to-rail input / output amplifier, and its bandwidth must meet the signal bandwidth requirements.

[0046] It should be noted that if Figure 6 The diagram shown is a circuit diagram of a low-pass filter. Figure 5In this design, the low-pass filter is a fourth-order active low-pass filter with a Sallen-Key circuit topology. The filter response parameters are designed according to Chebyshev parameters. Since the low-pass filter does not have a set gain and adopts a Sallen-Key topology, the circuit can condition the unipolar differential signal without providing an additional VCM common-mode voltage. The operational amplifier for the low-pass filter needs to be a single-supply rail-to-rail input / output amplifier, and its bandwidth must meet the signal bandwidth requirements.

[0047] In this embodiment, the low-pass filter in the signal conditioning circuit is connected to the microcontroller 60 via the analog-to-digital converter 50. The radio frequency filter circuit, signal amplification circuit 20, high-pass filter 30, low-pass filter, analog-to-digital converter 50, and microcontroller are connected in sequence. The low-pass filter is connected to the analog-to-digital converter 50 via a first voltage follower. The sensor state detection circuit 70 is connected to the analog-to-digital converter 50 via a second voltage follower. It should be noted that the operational amplifiers of the high-pass filter 30 and the low-pass filter, as well as the analog-to-digital converter 50, are all models that support single power supply mode.

[0048] It should be noted that the analog-to-digital converter 50 is used to convert analog signals into digital signals that the microcontroller 60 can process, and mainly measures two analog signals: one is the vibrating wire signal from the vibrating wire sensor, and the other is the feedback signal from the sensor state detection circuit 70, such as... Figure 7 The diagram shown is the circuit diagram of analog-to-digital converter 50. Figure 7 In the circuit, U6D is a voltage follower used as a buffer for the vibrating string signal input analog-to-digital converter 50, and U3D is a voltage follower used as a buffer for the feedback signal Vscm of the sensor state detection circuit 70.

[0049] In this embodiment, the vibrating string signal output by the sensor state detection circuit 70 passes sequentially through the radio frequency filter circuit, the first common-mode voltage sub-circuit, the signal amplification circuit 20, the high-pass filter 30, the low-pass filter and the analog-to-digital converter 50 before being sent to the microcontroller.

[0050] In this embodiment, the microcontroller 60 is responsible for processing and calculating the digital signals output by the analog-to-digital converter 50, and for controlling the operation of the sensor state detection circuit 70. Specifically, before each measurement, the microcontroller 60 outputs an enable signal to start the sensor state detection circuit 70, and then reads the circuit state signal data of the vibrating wire sensor through the analog-to-digital converter to determine whether the vibrating wire sensor is open-circuited or short-circuited. It should be noted that the microcontroller 60 is a conventional 32-bit microcontroller based on the Cortex-M3 architecture, which can meet the requirements of vibrating wire signal calculation and processing.

[0051] In practical implementation, the vibrating string signal conditioning circuit is powered by a single power supply. Then, the radio frequency filter circuit and the common-mode voltage circuit are connected to the signal conditioning circuit respectively. The signal conditioning circuit and the sensor state detection circuit 70 are both connected to the microcontroller 60. The sensor state detection circuit 70 is also connected to the radio frequency filter circuit. The vibrating string signal output by the sensor state detection circuit 70 is sent to the radio frequency filter circuit. After being processed by the radio frequency filter circuit, it flows to the common-mode voltage circuit to use the bipolar signal received by the common-mode voltage circuit to condition it into a unipolar signal. Then, the unipolar vibrating string signal flows sequentially to the signal conditioning circuit and the microcontroller. This allows the signal chain to work normally when the vibrating string signal conditioning circuit is powered by a single power supply. This is different from the existing technology and helps to reduce the complexity, cost and size of the vibrating string signal conditioning circuit, as well as the power consumption of the circuit.

[0052] It should be noted that the above implementation process is only to illustrate the feasibility of this application, but it does not mean that the vibrating wire signal conditioning circuit of this application has only one implementation process. On the contrary, as long as the vibrating wire signal conditioning circuit of this application can be implemented, it can be included in the feasible implementation scheme of this application.

[0053] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A vibrating-wire signal conditioning circuit, characterized in that: The vibrating-string signal conditioning circuit is powered by a single power supply, and includes a radio frequency filtering circuit, a common mode voltage circuit, a signal conditioning circuit, a sensor state detection circuit, and a microcontroller, wherein the radio frequency filtering circuit and the common mode voltage circuit are respectively connected to the signal conditioning circuit, and the common mode voltage circuit is used to condition a bipolar signal from the radio frequency filtering circuit into a unipolar signal, the signal conditioning circuit and the sensor state detection circuit are both connected to the microcontroller, and the sensor state detection circuit is connected to the radio frequency filtering circuit; The vibrating-string signal output by the sensor state detection circuit is sequentially transmitted through the radio frequency filter circuit, the common mode voltage circuit and the signal conditioning circuit, and is transmitted to the microcontroller.

2. The vibrating-wire signal conditioning circuit according to claim 1, characterized in that: The signal conditioning circuit is connected to the microcontroller via an analog-to-digital converter.

3. The vibrating-wire signal conditioning circuit according to claim 2, characterized in that: The signal conditioning circuit comprises a signal amplifying circuit, a high-pass filter and a low-pass filter. The radio frequency filtering circuit, the signal amplifying circuit, the high-pass filter, the low-pass filter, the analog-to-digital converter and the microcontroller are connected in sequence.

4. The vibrating-wire signal conditioning circuit according to claim 3, characterized in that: The common mode voltage circuit includes a first common mode voltage sub-circuit connected to the signal amplification circuit and a second common mode voltage sub-circuit connected to the high pass filter.

5. The vibrating-wire signal conditioning circuit according to claim 3, characterized in that: The signal amplification circuit is an instrument amplifier, which includes a gain resistor. The instrument amplifier amplifies the signal by the gain resistor.

6. The vibrating-wire signal conditioning circuit according to claim 3, characterized in that: The transition band attenuation rate of the high-pass filter is 40 dB / dec, the transition band attenuation rate of the low-pass filter is 80 dB / dec, and the input ends of the high-pass filter and the low-pass filter are both powered by a single power supply.

7. The vibrating-wire signal conditioning circuit according to claim 3, characterized in that: The low-pass filter is connected to the analog-to-digital converter via a first voltage follower, and the sensor state detection circuit is connected to the analog-to-digital converter via a second voltage follower.

8. The vibrating-wire signal conditioning circuit according to claim 1, characterized in that: The common mode voltage circuit provides a voltage that is half of the voltage provided by the power supply rail of the single power supply.

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