Vibration wire pressure sensor isolation detection circuit

Abstract

The utility model provides an isolation detection circuit of a vibrating wire pressure sensor. The isolation detection circuit comprises an MCU module, an isolation module and a detection module. The MCU module comprises an MCU chip; the isolation module comprises a power isolation chip and a signal isolation chip; the detection module comprises an oscillating circuit, an excitation loading circuit and a frequency acquisition circuit; the isolation detection circuit is connected with an external vibrating wire pressure sensor. According to the utility model, signals generated and received by the MCU module, high-voltage excitation signals and frequency signals returned by the vibrating wire pressure sensor are isolated, and the MCU module, the excitation loading circuit and the power supply positive terminal and the grounding terminal of the frequency acquisition circuit are also isolated, so that noise mutual interference generated by a digital circuit and an analog circuit is avoided; and the final detection result of the circuit is influenced.

Description

Technical Field

[0001] The utility model relates to the technical field of signal acquisition in the Internet of Things, and in particular to an isolation detection circuit for a vibrating-wire pressure sensor. Background Art

[0002] When the soil stress in the structure under test changes, the induction plate of the vibrating-wire pressure sensor will sense the stress change synchronously. The induction plate will produce deformation and transmit it to the vibrating wire, which will be converted into a change in the stress of the vibrating wire, thereby changing the vibration frequency of the vibrating wire. The electromagnetic coil excites the vibrating wire and measures its vibration frequency. The compressive stress value of the structure under test can be calculated, and the temperature value of the buried point can be measured synchronously. However, in actual engineering applications, due to factors such as electromagnetic effects, the isolation detection circuit is subject to greater interference, and the measured vibration frequency is inaccurate. Therefore, how to design a corresponding isolation detection circuit so that it has better anti-interference performance and obtains more accurate vibration frequency detection results has become an engineering problem that needs to be solved urgently. Utility Model Content

[0003] The utility model provides an isolation detection circuit for a vibrating-wire pressure sensor, which is characterized by:

[0004] Including MCU module, isolation module and detection module;

[0005] The MCU module includes an MCU chip;

[0006] The isolation module includes a power isolation chip and a signal isolation chip;

[0007] The detection module includes an oscillation circuit, an excitation loading circuit and a frequency acquisition circuit;

[0008] The isolation detection circuit is connected to an external vibrating-wire pressure sensor.

[0009] The MCU module generates a PWM signal;

[0010] The PWM signal enters the oscillation circuit in the detection module and is converted into a high-voltage excitation signal;

[0011] The high-voltage excitation signal is output through an excitation loading circuit in the detection module and loaded onto an external vibrating-wire pressure sensor.

[0012] The MCU module is used to generate the signal required by the isolation detection circuit as a whole, receive signal feedback, and perform calculation processing on the signal.

[0013] The power isolation chip in the isolation module is used to isolate and provide the power required by the isolation detection circuit, including the corresponding positive terminal and ground terminal;

[0014] The signal isolation chip in the isolation module is used to isolate the signal to ensure the correct transmission of the digital signal.

[0015] The oscillation circuit in the detection module generates a high voltage signal through an inductive oscillation circuit;

[0016] The excitation loading circuit in the detection module loads the high voltage signal onto an external vibrating-wire pressure sensor;

[0017] The frequency acquisition circuit in the detection module collects the frequency signal sent back by the vibrating-wire pressure sensor, and further filters and amplifies it, and finally sends the signal to the MCU module.

[0018] The MCU module includes a main control MCU chip U1, whose pins generate four output signals, namely PWM, HV_EN, HV_RELESE, and KY_EN;

[0019] The main control MCU chip U1 receives two input signals, namely HV_ADC and SEN_OUT;

[0020] The signal isolation chip in the isolation module specifically includes two chips, U2 and U3, both ends of which use different positive power terminals and ground terminals;

[0021] The isolation signals of the U2 chip are: PWM, HV_EN, HV_RELASE, KY_EN are input at one end, and PWM1, HV_EN1, HV_RELASE1, KY_EN1 are output at the other end;

[0022] The isolation signals of the U3 chip are respectively input KY_ADC1 and SEN_OUT1 at one end and output HV_ADC and SEN_OUT at the other end;

[0023] The isolation module also includes a power isolation chip U4, which is used to completely isolate the positive power terminal and ground terminal of the MCU module on the circuit board from the positive power terminal and ground terminal used by the analog signal circuit to prevent the digital circuit of the MCU module from interfering with the analog circuit of the detection module.

[0024] The oscillation circuit in the detection module includes:

[0025] Transistor Q1, NMOS tube Q2, resistors R1, R2, R3 form a power switch circuit, which is used to control the power switch; when HV_EN1 is high, power is added to the inductor L1; when HV_EN1 is low, the power on L1 will be turned off;

[0026] Resistors R4, R5, transistor Q3, and inductor L1 form a boost circuit, which is used to increase the voltage of the PWM signal;

[0027] D1, D2, and C1 form a rectifier charging circuit, where D1 and D2 are rectifier diodes and C1 is a high-voltage capacitor. The high voltage passes through diodes D1, D2 and capacitor C1, rectifies the voltage-boosted PWM signal into a DC voltage signal, and charges capacitor C1 to store energy.

[0028] The isolation detection circuit also includes a high-voltage excitation circuit. When the capacitor C1 is fully charged, KY_EN1 is set high, the relay K1 is connected to the external vibrating-wire pressure sensor S1, HV_RELEASE1 is set high, the Q4 thyristor is turned on, and the high-voltage signal is released to the vibrating-wire pressure sensor S1.

[0029] When a high voltage excitation is applied to the external vibrating-wire pressure sensor, the vibrating-wire pressure sensor oscillates and a vibrating-wire signal HV_OUT of a certain frequency appears.

[0030] The frequency acquisition circuit in the detection module is divided into three levels;

[0031] The first stage is the Z3 voltage regulator, the D6 diode, and the op amp U5:A to buffer the signal and limit the signal;

[0032] The second stage is composed of capacitors C5, C6, resistors R13, R15, and operational amplifier U5:B, which form a low-pass filter and amplifier circuit to filter out noise and obtain the detected frequency signal;

[0033] The third stage is composed of resistors R18 and R19, and op amp U5:C forms a comparator circuit to generate a SEN_OUT1 signal, which is a frequency signal for processing by the MCU module. The MCU module converts it into a detectable frequency signal through counting and timer functions.

[0034] The MCU module includes the following working steps:

[0035] The MCU module generates PWM signals;

[0036] Set RELEASE to low level and HV_EN to high level;

[0037] Check whether HV_ADC is greater than or equal to 3V;

[0038] When HV_ADC is less than 3V, adjust the PWM signal duty cycle and return to check whether HV_ADC is greater than or equal to 3V;

[0039] When HV_ADC is greater than or equal to 3V, KY_EN is set high, the relay is closed, RELEASE is set high, the high voltage is released, HV_EN is set low, and the PWM signal is turned off;

[0040] The MCU module starts counting and timer functions;

[0041] Read SEN_OUT to get the measured frequency value.

[0042] The utility model isolates the signals generated and received by the MCU module, the high-voltage excitation signal and the frequency signal returned by the vibrating-string pressure sensor, and also isolates the positive power terminal and the ground terminal of the MCU module, the excitation loading circuit and the frequency acquisition circuit, so as to avoid noise interference between the digital circuit and the analog circuit, thereby affecting the final detection result of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The utility model is a composition of an isolation detection circuit of a vibrating-wire pressure sensor.

[0044] Figure 2 It is the specific structure of the power isolation chip and signal isolation chip in the MCU module and the isolation module.

[0045] Figure 3 It is the specific structure of the oscillation circuit and the excitation loading circuit in the detection module.

[0046] Figure 4 It is the specific structure of the frequency acquisition circuit in the detection module.

[0047] Figure 5 This is the working process of the MCU module of the isolation detection circuit of the vibrating-wire pressure sensor of the utility model. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the present application scheme, the technical scheme of the present utility model will be described in detail below with reference to the accompanying drawings.

[0049] [Example 1]

[0050] like Figure 1 As shown, the utility model provides a vibrating-string pressure sensor isolation detection circuit, comprising an MCU module, an isolation module, and a detection module; the MCU module comprises an MCU chip; the isolation module comprises a power isolation chip and a signal isolation chip; the detection module comprises an oscillation circuit, an excitation loading circuit, and a frequency acquisition circuit; the isolation detection circuit is connected to an external vibrating-string pressure sensor.

[0051] The basic method of collecting and measuring the frequency of the vibrating wire pressure signal in the utility model is:

[0052] The MCU module generates a PWM signal; the PWM signal enters the oscillation circuit in the detection module and is converted into a high-voltage excitation signal; the high-voltage excitation signal is output through the excitation loading circuit in the detection module and loaded onto an external vibrating-wire pressure sensor.

[0053] In response to the high-voltage excitation signal, the vibrating-wire pressure sensor generates a frequency signal and transmits it back to the frequency acquisition circuit in the detection module; the frequency acquisition circuit filters and amplifies the frequency signal. After the MCU module turns on the counting and timer functions, the frequency signal is input into the MCU module so that the MCU module can measure the signal frequency.

[0054] In a possible implementation, the above-mentioned basic signal frequency isolation detection circuit is further improved: the signals generated and received by the MCU module, the high-voltage excitation signal, and the frequency signal returned by the vibrating-string pressure sensor are isolated; the positive power supply terminal and the ground terminal of the MCU module, the excitation loading circuit, and the frequency acquisition circuit are also isolated.

[0055] By isolating the above signals and isolating the power supply of the detection module and the MCU module at the same time, it is avoided that the digital circuit and the analog circuit generate noise and interfere with each other, thereby preventing the final detection result of the circuit from being affected.

[0056] In this embodiment, the MCU module is used to generate the signal required by the isolation detection circuit as a whole, receive signal feedback, and calculate and process the signal; the power isolation chip in the isolation module is used to isolate and provide the power required by the isolation detection circuit, including the corresponding positive terminal and ground terminal; the signal isolation chip in the isolation module has strong insulation capabilities, which helps prevent noise and surges on the data bus or other circuits from entering the local ground terminal, thereby interfering with or damaging sensitive circuits, and high CMTI capabilities can ensure the correct transmission of digital signals to achieve the purpose of isolating signals; the oscillation circuit in the detection module generates a 200V high-voltage signal through an inductive oscillation circuit; the excitation loading circuit in the detection module loads the 200V high-voltage signal on an external vibrating-wire pressure sensor; the frequency acquisition circuit in the detection module collects the frequency signal sent back by the vibrating-wire pressure sensor, and further filters and amplifies it, and finally sends the signal to the MCU module. [Example 2] Figure 2Another possible implementation of the utility model includes an MCU module, a power isolation chip in an isolation module, and a signal isolation chip. The MCU module includes a main control MCU chip U1, whose pins generate four output signals, namely PWM, HV_EN, HV_RELESE, and KY_EN; the output signal is valid at a high level, and the frequency of the PWM signal can be specifically 20kHz; the main control MCU chip U1 receives two input signals, namely HV_ADC and SEN_OUT. The signal isolation chip in the isolation module specifically includes two chips, U2 and U3, which adopt fully differential isolation capacitor technology. The high-voltage isolation capacitor composed of SiO2 provides a reliable insulation barrier and a reliable signal transmission path between different voltage domains to achieve signal isolation; in order to ensure stable data transmission quality, the signal isolation chip also introduces on-off keying (OOK) modulation and demodulation technology. Transmission (TX) modulates the input signal to the carrier frequency, that is, TX transmits a high-frequency signal through the isolation capacitor in one input state, and no signal passes through the isolation capacitor in another input state, and then the receiver reconstructs the input signal according to the detected in-band data. This architecture provides a reliable data transmission path between isolated voltage domains, without the need to consider initialization at startup. The fully differential isolation capacitor architecture can maximize the signal common mode transient interference resistance. The advanced circuit technology of the digital isolator chip can effectively suppress the EMI introduced by the carrier signal and IO switch. Compared with the inductive coupling isolation architecture, the capacitive coupling architecture has stronger electromagnetic interference resistance. The OOK modulation scheme eliminates the bit error caused by the pulse loss that may occur in the pulse modulation scheme.

[0057] The two chips U2 and U3 use different positive power supply terminals and ground terminals at both ends; the isolation signals of the U2 chip are: PWM, HV_EN, HV_RELASE, KY_EN are input at one end, and PWM1, HV_EN1, HV_RELASE1, KY_EN1 are output at the other end; the isolation signals of the U3 chip are: KY_ADC1 and SEN_OUT1 are input at one end, and HV_ADC and SEN_OUT are output at the other end.

[0058] The isolation module also includes a power isolation chip U4, which is used to completely isolate the positive power terminal and ground terminal of the MCU module on the circuit board from the positive power terminal and ground terminal used by the analog signal circuit to prevent the digital circuit of the MCU module from interfering with the analog circuit of the detection module.

[0059] [Example 3]

[0060] Figure 3As another possible implementation of the utility model, the specific structure of the oscillation circuit and the excitation loading circuit in the detection module is disclosed; the oscillation circuit part generates a high voltage of 200V.

[0061] Transistor Q1, NMOS tube Q2, resistors R1, R2, R3 form a power switch circuit for controlling the power switch; when HV_EN1 is at a high level, power is added to the inductor L1; when HV_EN1 is at a low level, the power on L1 will be turned off.

[0062] Resistors R4, R5, transistor Q3, and inductor L1 form a boost circuit, where L1 uses a high Q value inductor, and Q3 can be a specific MMBTA42, which has a high V CEO =300V; when the PWM1 signal is added to the resistor R4 end, it is amplified by Q3, L1 oscillates, and one end of L1 can reach a high voltage of 200V.

[0063] D1, D2, and C1 form a rectifier charging circuit, where D1 and D2 are rectifier diodes and C1 is a high-voltage capacitor, which can be 2.2μF / 400V. The high voltage passes through diodes D1, D2 and capacitor C1 to rectify the voltage-boosted PWM signal into a DC voltage signal, and at the same time charge capacitor C1 to store energy.

[0064] R6, R7, Z2, C2 form a voltage-dividing sampling circuit, specifically R6 = 1MΩ, R7 = 17kΩ, and C2 can be a normal capacitor or a high-voltage capacitor. At this time, the MCU module reads HV_ADC1, and when HV_ADC1 = 3V, the capacitor C1 is fully charged, and the MCU module controls HV_EN1 to be low, turning off charging.

[0065] When capacitor C1 is fully charged, KY_EN1 is set high, relay K1 is connected to the external vibrating-wire pressure sensor S1, HV_RELEASE1 is set high, Q4 thyristor is turned on, and the high-voltage signal is released to the vibrating-wire pressure sensor S1.

[0066] [Example 4]

[0067] Figure 4 As another possible implementation of the utility model, a specific structure of a frequency acquisition circuit in a detection module is disclosed.

[0068] When a high voltage excitation is applied to the external vibrating-wire pressure sensor, the vibrating-wire pressure sensor oscillates and a vibrating-wire signal HV_OUT of a certain frequency appears.

[0069] The frequency acquisition circuit in the detection module is divided into three levels:

[0070] The first stage is the Z3 voltage regulator, the D6 diode, and the op amp U5:A to buffer the signal and limit the signal;

[0071] The second stage is composed of capacitors C5, C6, resistors R13, R15, and operational amplifier U5:B, which form a low-pass filter and amplifier circuit to filter out noise and obtain the detected frequency signal;

[0072] The third stage is composed of resistors R18 and R19, and op amp U5:C forms a comparator circuit to generate a SEN_OUT1 signal, which is a frequency signal for processing by the MCU module. The MCU module converts it into a detectable frequency signal through counting and timer functions.

[0073] [Example 5]

[0074] Figure 5 As another possible implementation of the utility model, the working steps of the MCU module of the vibrating-wire pressure sensor isolation detection circuit are disclosed.

[0075] S1: The MCU module generates a PWM signal, which may be 20kHz;

[0076] S2: Set RELEASE to low level and HV_EN to high level;

[0077] S3: Check whether HV_ADC is greater than or equal to 3V; when HV_ADC is less than 3V, execute S4; when HV_ADC is greater than or equal to 3V, execute S5;

[0078] S4: adjust the duty cycle of the PWM signal and return to S3;

[0079] S5: Set KY_EN to high, the relay is closed, set RELEASE to high level, the high voltage is released, set HV_EN to low level, and turn off the PWM signal;

[0080] S6: MCU module starts counting and timer functions;

[0081] S7: Read SEN_OUT to obtain the measured frequency value.

Claims

1. A vibrating wire pressure sensor isolation detection circuit, characterized in that: Including MCU module, isolation module and detection module; The MCU module includes an MCU chip; The isolation module includes a power isolation chip and a signal isolation chip; The detection module includes an oscillation circuit, an excitation loading circuit and a frequency acquisition circuit; The isolation detection circuit is connected to an external vibrating-wire pressure sensor.

2. The vibrating wire pressure sensor isolation detection circuit according to claim 1, characterized in that: The MCU module generates a PWM signal; The PWM signal enters the oscillation circuit in the detection module and is converted into a high-voltage excitation signal; The high-voltage excitation signal is output through an excitation loading circuit in the detection module and loaded onto an external vibrating-wire pressure sensor.

3. The vibrating wire pressure sensor isolation detection circuit according to claim 1, characterized in that: The MCU module is used to generate the signal required by the isolation detection circuit as a whole, receive signal feedback, and perform calculation processing on the signal.

4. The vibrating wire pressure sensor isolation detection circuit according to claim 1, characterized in that: The power isolation chip in the isolation module is used to isolate and provide the power required by the isolation detection circuit, including the corresponding positive terminal and ground terminal; The signal isolation chip in the isolation module is used to isolate the signal to ensure the correct transmission of the digital signal.

5. The vibrating wire pressure sensor isolation detection circuit according to claim 1, characterized in that: The oscillation circuit in the detection module generates a high voltage signal through an inductive oscillation circuit; The excitation loading circuit in the detection module loads the high voltage signal onto an external vibrating-wire pressure sensor; The frequency acquisition circuit in the detection module collects the frequency signal sent back by the vibrating-wire pressure sensor, and further filters and amplifies it, and finally sends the signal to the MCU module.

6. The vibrating wire pressure sensor isolation detection circuit according to claim 1 or 2, characterized in that: The MCU module includes a main control MCU chip U1, whose pins generate four output signals, namely PWM, HV_EN, HV_RELESE, and KY_EN; The main control MCU chip U1 receives two input signals, namely HV_ADC and SEN_OUT; The signal isolation chip in the isolation module specifically includes two chips, U2 and U3, both ends of which use different positive power terminals and ground terminals; The isolation signals of the U2 chip are: PWM, HV_EN, HV_RELASE, KY_EN are input at one end, and PWM1, HV_EN1, HV_RELASE1, KY_EN1 are output at the other end; The isolation signals of the U3 chip are respectively input KY_ADC1 and SEN_OUT1 at one end and output HV_ADC and SEN_OUT at the other end; The isolation module also includes a power isolation chip U4, which is used to completely isolate the positive power terminal and ground terminal of the MCU module on the circuit board from the positive power terminal and ground terminal used by the analog signal circuit to prevent the digital circuit of the MCU module from interfering with the analog circuit of the detection module.

7. The vibrating wire pressure sensor isolation detection circuit according to claim 1 or 2, characterized in that: The oscillation circuit in the detection module includes: Transistor Q1, NMOS tube Q2, resistors R1, R2, R3 form a power switch circuit, which is used to control the power switch; when HV_EN1 is high, power is added to the inductor L1; when HV_EN1 is low, the power on L1 will be turned off; Resistors R4, R5, transistor Q3, and inductor L1 form a boost circuit, which is used to increase the voltage of the PWM signal; D1, D2, and C1 form a rectifier charging circuit, where D1 and D2 are rectifier diodes and C1 is a high-voltage capacitor. The high voltage passes through diodes D1, D2 and capacitor C1, rectifies the voltage-boosted PWM signal into a DC voltage signal, and charges capacitor C1 to store energy. The isolation detection circuit also includes a high-voltage excitation circuit. When the capacitor C1 is fully charged, KY_EN1 is set high, the relay K1 is connected to the external vibrating-wire pressure sensor S1, HV_RELEASE1 is set high, the Q4 thyristor is turned on, and the high-voltage signal is released to the vibrating-wire pressure sensor S1.

8. The vibrating wire pressure sensor isolation detection circuit according to claim 1 or 2, characterized in that: When a high voltage excitation is applied to the external vibrating-wire pressure sensor, the vibrating-wire pressure sensor oscillates and a vibrating-wire signal HV_OUT of a certain frequency appears.

9. The vibrating wire pressure sensor isolation detection circuit according to claim 8, characterized in that: The frequency acquisition circuit in the detection module is divided into three levels; The first stage is the Z3 voltage regulator, the D6 diode, and the op amp U5:A to buffer the signal and limit the signal; The second stage is composed of capacitors C5, C6, resistors R13, R15, and operational amplifier U5:B, which form a low-pass filter and amplifier circuit to filter out noise and obtain the detected frequency signal; The third stage is composed of resistors R18 and R19, and op amp U5:C forms a comparator circuit to generate a SEN_OUT1 signal, which is a frequency signal for processing by the MCU module. The MCU module converts it into a detectable frequency signal through counting and timer functions.

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