CN219204469U - Noise signal processing circuit - Google Patents

Abstract

The utility model provides a noise signal processing circuit, and belongs to the technical field of pipeline water leakage noise detection. The utility model comprises a charge amplifier, a trap, a band-pass filter, a programmable gain amplifier and a microprocessor which are sequentially connected, wherein a digital potentiometer is arranged in the band-pass filter, and the microprocessor is respectively connected with the digital potentiometer and the programmable gain amplifier; the charge amplifier is used for amplifying the charge signal and converting the charge signal into a voltage signal; the wave trap is used for filtering interference in the equipment; the band-pass filter adjusts a passband by changing the resistance gear of the digital potentiometer, and filters and amplifies noise signals; the programmable gain amplifier is used for adjusting the amplitude gain of the noise signal and compensating the gain change when the passband of the band-pass filter is changed; the microprocessor adjusts the gears of the digital potentiometer and the programmable gain amplifier according to the sampling signal. The utility model can dynamically adjust the gain and the filtering frequency range of the water leakage noise signal and more accurately analyze the water leakage condition of the pipeline.

Description

Noise signal processing circuit

Technical Field

The utility model relates to the technical field of pipeline water leakage noise detection, in particular to a noise signal processing circuit.

Background

The urban water supply industry is taken as one of the most important infrastructure industries in national economy, is not only an important component for accelerating the whole planning system of the urban process, but also has important significance for coordinating the dynamic relationship among life, production and ecology and maintaining the sustainable development of the economic society. The method has obvious effect of reducing the leakage rate of the urban water supply pipe network in China, but the leakage rate in local areas is still high. The statistical annual survey published by the residential and urban construction department 2020, 12 and 31 months, shows that the water leakage of public water supply in the national city and county in 2019 reaches 95.37 hundred million cubic meters, which is approximately equal to the water storage capacity of 700 Hangzhou western lakes, and according to experience, the water leakage of the city in China is only higher than the figure. The demand for the leakage rate of the public water supply network is higher and higher, and the leakage of the public water supply network enters the stage of normalized monitoring and optimizing treatment in the future, so that new monitoring means and tools are necessary.

The frequency of the water leakage noise signal of the pipe network is mainly concentrated between 50Hz and 2.5KHz, the common means of the water leakage noise monitoring equipment is to collect the sound wave signal on the water supply pipe network by adopting a piezoelectric sensor, analyze the signal of the water leakage noise frequency band through filtering and amplifying, and obtain the conclusion of whether water leakage exists in the pipe. However, sometimes, because other noise filtering effects in the signal are not ideal, noise interference is too large, and the situation that a signal at a certain frequency point is suspected to leak but is difficult to determine occurs, if the analysis method is improper, false alarm is likely to be caused, and inconvenience is brought to detecting whether a pipeline leaks or not.

Because of the influence of factors such as the installation environment of pipe network, pipeline material, etc., noise signal intensity on the pipe network is different, and the charge signal amplitude span that piezoelectric sensor detected is relatively big, is generally between microvolts level and millivolts level, therefore when the gain of signal processing circuit is fixed, probably can lead to microprocessor sampling signal amplitude too little inconvenient analysis because of signal amplification factor is too little, or the signal amplitude distortion is led to the amplitude too big after the signal amplification, these all have influenced the analysis judgement of pipe network water leakage.

Disclosure of Invention

Aiming at the technical problems that the gain and the filtering frequency of a signal processing circuit of the existing water leakage noise monitoring equipment are fixed and influence the analysis and judgment of water leakage of a pipeline, the utility model provides a noise signal processing circuit and a noise signal processing method.

In order to achieve the above purpose, the technical scheme of the utility model is realized as follows: a noise signal processing circuit comprises a charge amplifier, a trap, a band-pass filter, a programmable gain amplifier and a microprocessor which are sequentially connected, wherein a digital potentiometer is arranged in the band-pass filter, and the microprocessor is respectively connected with the digital potentiometer and a gear of the programmable gain amplifier; the charge amplifier is used for amplifying a charge signal generated by the piezoelectric sensor and converting the charge signal into a voltage signal; the wave trap is used for filtering 50Hz power frequency interference in equipment; the band-pass filter adjusts a passband by changing the resistance gear of the digital potentiometer, filters and amplifies noise signals; the programmable gain amplifier is used for adjusting the amplitude gain of the noise signal and compensating the gain change when the passband of the band-pass filter is changed; and the microprocessor adjusts the gears of the digital potentiometer and the programmable gain amplifier according to the sampling signals, adjusts the signal gain and the passband of the bandpass filter, and analyzes whether water leakage occurs.

Preferably, the band-pass filter comprises a low-pass filter and a high-pass filter, wherein the input end of the low-pass filter is connected with the trap, the output end of the low-pass filter is connected with the input end of the high-pass filter, and the output end of the high-pass filter is connected with the programmable gain amplifier; and digital potentiometers are arranged in the low-pass filter and the high-pass filter, and the gear of the digital potentiometers is connected with the microprocessor.

Preferably, the charge amplifier comprises a first operational amplifier, wherein the non-inverting input end of the first operational amplifier is connected with a reference voltage source, the inverting input end of the first operational amplifier is connected with the positive electrode of the piezoelectric sensor through a capacitor C1, the inverting input end of the first operational amplifier is connected with the output end of the first operational amplifier through a connecting circuit, and the output end of the first operational amplifier is connected with the input end of the trap; the connecting circuit comprises a capacitor C2, a resistor R1, a resistor R2 and a resistor R3, wherein the inverting input end of the first operational amplifier is respectively connected with one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is connected with the output end of the first operational amplifier, the other end of the resistor R2 is respectively connected with one end of the resistor R1 and one end of the resistor R3, the other end of the resistor R1 is connected with a reference voltage source, and the other end of the resistor R3 is connected with the output end of the first operational amplifier; signal gain of charge amplifier

Preferably, the trap comprises a double-T-shaped RC filter, a second operational amplifier and a third operational amplifier, the double-T-shaped RC filter comprises a T-shaped low-pass filter and a T-shaped high-pass filter which are connected in parallel, one ends of T-shaped transverse ends of the T-shaped low-pass filter and the T-shaped high-pass filter are connected with the output end of a first operational amplifier of the charge amplifier, the other ends of the T-shaped transverse ends of the T-shaped low-pass filter and the T-shaped high-pass filter are connected with the non-inverting input end of the third operational amplifier, the inverting input end of the third operational amplifier is connected with the output end of the third operational amplifier, the output end of the third operational amplifier is connected with the input end of a low-pass filter of the band-pass filter and the feedback circuit I of the band-pass filter respectively, the inverting input end of the second operational amplifier is connected with the output end of the second operational amplifier, and the output end of the second operational amplifier is connected with the T-shaped longitudinal ends of the T-shaped low-pass filter and the T-shaped high-pass filter respectively.

Preferably, the T-type high-pass filter includes a capacitor C3, a capacitor C5 and a resistor R5, one end of the capacitor C3 is connected to the output end of the first operational amplifier, the other end of the capacitor C3 is connected to one end of the capacitor C5 and one end of the resistor R5, the other end of the capacitor C5 is connected to the non-inverting input end of the third operational amplifier, and the other end of the resistor R5 is connected to the output end of the second operational amplifier; the T-shaped low-pass filter comprises a resistor R4, a resistor R6 and a capacitor C4, wherein one end of the resistor R4 is connected with one end of the capacitor C3, the other end of the resistor R4 is respectively connected with one end of the resistor R6 and one end of the capacitor C4, the other end of the resistor R6 is connected with the non-inverting input end of the third operational amplifier, and the other end of the capacitor C4 is connected with the output end of the second operational amplifier; the feedback circuit I comprises a resistor R7 and a resistor R8, one end of the resistor R7 is connected with the output end of the third operational amplifier, the other end of the resistor R7 is respectively connected with one end of the resistor R8 and the non-inverting input end of the second operational amplifier, and the other end of the resistor R8 is grounded.

Preferably, the low-pass filter comprises a fourth operational amplifier and a first digital potentiometer, wherein the non-inverting input end of the fourth operational amplifier is connected with a reference voltage source, the inverting input end of the fourth operational amplifier is respectively connected with one end of a resistor R9 and one end of a capacitor C7, the other end of the resistor R9 is connected with the output end of the third operational amplifier of the trap, the other end of the capacitor C7 is connected with the output end of the fourth operational amplifier, and the output end of the fourth operational amplifier is connected with the input end of the high-pass filter; the first digital potentiometer is connected in parallel with two ends of the capacitor C7; the high-pass filter comprises a fifth operational amplifier, a second digital potentiometer and a third digital potentiometer, and the fifth operationThe non-inverting input end of the amplifier is connected with a reference voltage source, the inverting input end of the fifth operational amplifier is respectively connected with one end of a capacitor C10 and one end of a second digital potentiometer, the other end of the second digital potentiometer is connected with the output end of the fifth operational amplifier, and the output end of the fifth operational amplifier is connected with the input end of the programmable gain amplifier; the other end of the capacitor C10 is respectively connected with one end of the capacitor C8, one end of the capacitor C9 and one end of the third digital potentiometer, the other end of the capacitor C8 is connected with the output end of the fourth operational amplifier, the other end of the capacitor C9 is connected with the output end of the fifth operational amplifier, and the other end of the third digital potentiometer is grounded; the resistance values of the second digital potentiometer and the third digital potentiometer are kept in a fixed proportional relation; the cut-off frequency of the low-pass filter is

Passband voltage amplification is +.>

The pass band voltage amplification factor of the high pass filter is +.>

Cut-off frequency is +.>

Wherein, RP1 is the resistance of the first digital potentiometer, RP2 is the resistance of the second digital potentiometer, and RP3 is the resistance of the third digital potentiometer.

Preferably, the programmable gain amplifier comprises a programmable gain amplifying chip, a front-end operational amplifier and a programmable gain operational amplifier are arranged in the programmable gain amplifying chip, an inverting input end of the front-end operational amplifier is connected with an output signal of the high-pass filter through an input resistor R10 and a direct-current blocking capacitor C12, a non-inverting input end of the front-end operational amplifier is connected with a reference voltage source, an output end of the front-end operational amplifier is connected with an inverting input end of the front-end operational amplifier through a feedback resistor R12, an inverting input end of the programmable gain operational amplifier is connected with an output end of the front-end operational amplifier, a non-inverting input end of the programmable gain operational amplifier is connected with a reference voltage source, and an output end of the programmable gain operational amplifier is connected with the microprocessor through a resistor R17;

the programmable gain amplification chip is provided with three gear adjusting interfaces, and the gear adjusting interfaces are connected with the microprocessor through an adjusting circuit and adjust gain according to commands of the microprocessor; the signal amplification factor of the programmable gain amplifier is

Gain values for different gain stages; the adjusting circuit comprises a resistor R13, a resistor R14 and a capacitor C13 which are connected with the first gear adjusting interface, a resistor R15, a resistor R16 and a capacitor C14 which are connected with the second gear adjusting interface, and a resistor R20, a resistor R22 and a capacitor C16 which are connected with the third gear adjusting interface; the first gear adjusting interface is respectively connected with one end of a resistor R13, one end of a resistor R14 and one end of a capacitor C13, the other end of the resistor R13 and the other end of the capacitor C13 are grounded, and the other end of the resistor R14 is connected with a microprocessor; the second gear adjusting interface is respectively connected with one end of a resistor R15, one end of a resistor R16 and one end of a capacitor C14, the other end of the resistor R15 and the other end of the capacitor C14 are grounded, and the other end of the resistor R16 is connected with a microprocessor; the third gear adjusting interface is respectively connected with one end of a resistor R20, one end of a resistor R21 and one end of a capacitor C16, the other end of the resistor R20 and the other end of the capacitor C16 are grounded, and the other end of the resistor R22 is connected with a microprocessor;

the first digital potentiometer, the second digital potentiometer and the third digital potentiometer comprise digital potentiometer chips, VDD pins of the digital potentiometer chips are connected with a voltage source, VSS pins of the digital potentiometer chips are grounded, SCL pins and SDA pins of the digital potentiometer chips are connected with a microprocessor, SCL pins are connected with the voltage source through resistors R36, SDA pins are connected with the voltage source through resistors R37, W pins of the digital potentiometer chips are used as input ends, and B pins are used as output ends and are respectively connected with a low-pass filter or a high-pass filter.

The utility model has the beneficial effects that: for original water leakage noise signals acquired by different pipe network installation environments, different materials and different sensors, the signal gain can be automatically adjusted according to the signal amplitude, so that the conditions that the analysis is inconvenient due to too small signal amplification factor or the analysis and judgment are affected due to signal distortion and the like due to too large signal amplification factor are avoided, the application range of the water leakage noise monitoring equipment is wider, and the limitation of factors such as the environment and the materials is reduced; when other signal noise interference is too large and whether water leakage phenomenon exists cannot be determined, analysis can be performed on suspected water leakage signal frequency points, the passband frequency width of the filter is dynamically adjusted, gain change caused by cut-off frequency change of the filter is compensated, and better and more accurate analysis of pipe network water leakage is facilitated. The utility model can dynamically adjust the gain and the filtering frequency range of the water leakage noise signal, and can realize more accurate analysis of the water leakage condition of the pipeline.

Drawings

In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a noise signal processing circuit of the present utility model.

Fig. 2 is a circuit diagram of the charge amplifier of fig. 1 according to the present utility model.

Fig. 3 is a circuit diagram of the trap of fig. 1 in accordance with the present utility model.

Fig. 4 is a circuit diagram of the low pass filter of fig. 1 in accordance with the present utility model.

Fig. 5 is a circuit diagram of the high pass filter of fig. 1 in accordance with the present utility model.

Fig. 6 is a circuit diagram of the programmable gain amplifier of fig. 1 in accordance with the present utility model.

Fig. 7 is a circuit diagram of the digital potentiometer of fig. 1 according to the present utility model.

Fig. 8 is a flow chart of a method of the noise signal processing circuit of the present utility model.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without any inventive effort, are intended to be within the scope of the utility model.

Example 1

As shown in fig. 1, a noise signal processing circuit comprises a charge amplifier, a trap, a band-pass filter, a programmable gain amplifier and a microprocessor which are sequentially connected, wherein a digital potentiometer is arranged in the band-pass filter, and the microprocessor is respectively connected with the digital potentiometer and the gear of the programmable gain amplifier; the charge amplifier is used for amplifying a charge signal generated by the piezoelectric sensor and converting the charge signal into a voltage signal; the trap is a band-stop filter with the center frequency of 50Hz, and is used for filtering 50Hz power frequency interference in water leakage monitoring equipment, so that erroneous judgment is avoided; the band-pass filter adjusts a passband by changing the resistance gear of the digital potentiometer, filters and amplifies noise signals; the programmable gain amplifier is used for adjusting the amplitude gain of the noise signal and compensating the gain change when the passband of the band-pass filter is changed; and the microprocessor adjusts the gears of the digital potentiometer and the programmable gain amplifier according to the sampling signals, adjusts the signal gain and the passband of the bandpass filter, and analyzes whether water leakage occurs.

Further, the band-pass filter comprises a low-pass filter and a high-pass filter, the input end of the low-pass filter is connected with the trap, the output end of the low-pass filter is connected with the input end of the high-pass filter, and the output end of the high-pass filter is connected with the programmable gain amplifier; and digital potentiometers are arranged in the low-pass filter and the high-pass filter, and the gear of the digital potentiometers is connected with the microprocessor. The low-pass filter changes the upper limit frequency of the passband by adjusting the cutoff frequency; the high pass filter changes the lower limit frequency of the passband by adjusting the cutoff frequency. The programmable gain amplifier is connected with the high-pass filter, so that the signal gain is always kept in a proper range, and the data analysis of the microprocessor is not influenced by the overlarge or undersize signal amplitude; the microprocessor collects the output signal of the programmable gain amplifier, judges whether leakage occurs according to the analysis result, or adjusts the gear of the digital potentiometer or the programmable gain amplifier when the leakage cannot be determined, and collects the signal again for analysis.

As shown in fig. 2, the charge amplifier includes a first operational amplifier U1A, the non-inverting input end of the first operational amplifier is connected to a reference voltage source Vref, the inverting input end of the first operational amplifier U1A is connected to the positive electrode of the piezoelectric sensor through a capacitor C1, the capacitor C1 is an input capacitor of the operational amplifier U1A, the capacitor C2 is a feedback capacitor, and the gain of the charge amplifier is the capacitance-to-reactance ratio of the feedback capacitor C2 to the capacitor C1. The negative electrode of the piezoelectric sensor is respectively grounded and the positive electrode of the diode D1, the negative electrode of the diode D1 is respectively connected with the positive electrode of the piezoelectric sensor and the positive electrode of the diode D2, and the negative electrode of the diode D2 is grounded. The high-voltage signal generated by the piezoelectric sensor is grounded and filtered through the diode D1 and the diode D2, and is prevented from entering the operational amplifier. The inverting input end of the first operational amplifier is connected with the output end of the first operational amplifier through a connecting circuit, and the output end of the first operational amplifier is connected with the input end of the trap. The charge amplifier amplifies weak charge signals on the piezoelectric sensor into voltage signals with higher amplitude, so that the signal processing of a later-stage circuit is facilitated, the working frequency range of the charge amplifier is very wide, and the signal gain is fixed in the water leakage noise frequency range. The 4 th pin of the first operational amplifier is respectively connected with one end of a power supply and one end of a capacitor C6, the other end of the capacitor C6 is grounded, and the 11 th pin of the first operational amplifier is grounded. The capacitor C6 is a power supply filter capacitor and is used for filtering power supply signal interference.

The connecting circuit comprises a capacitor C2, a resistor R1, a resistor R2 and a resistor R3, wherein the inverting input end of the first operational amplifier is respectively connected with one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is connected with the output end of the first operational amplifier, and the other end of the resistor R2 is respectively connected with one end of the resistor R1And one end of the resistor R3, the other end of the resistor R1 is connected with a reference voltage source Vref, and the reference voltage source has the function of pulling up all signals to the vicinity of the reference voltage source, so that all signals are positive voltage signals and are convenient to process and analyze. The other end of the resistor R3 is connected with the output end of the first operational amplifier. The capacitor C2, the resistor R1, the resistor R2 and the resistor R3 form a filter circuit, and the working frequency range of the charge amplifier can be adjusted. Signal gain of charge amplifier

As shown in fig. 3, the trap comprises a double-T-shaped RC filter, a second operational amplifier U1B and a third operational amplifier U1C, the double-T-shaped RC filter comprises a T-shaped low-pass filter and a T-shaped high-pass filter which are connected in parallel, the T-shaped low-pass filter and the T-shaped high-pass filter are two single-T-shaped networks, and the T-shaped low-pass filter and the T-shaped high-pass filter are connected in parallel to form a band-stop filter. One end of the T-shaped transverse end of the T-shaped low-pass filter and one end of the T-shaped transverse end of the T-shaped high-pass filter are connected with the output end of the first operational amplifier of the charge amplifier, the other end of the T-shaped transverse end of the T-shaped low-pass filter and one end of the T-shaped transverse end of the T-shaped high-pass filter are connected with the non-inverting input end of the third operational amplifier, the inverting input end of the third operational amplifier is connected with the output end of the third operational amplifier, the output end of the third operational amplifier is respectively connected with the input end of the low-pass filter of the band-pass filter and the feedback circuit I, the feedback circuit I is connected with the non-inverting input end of the second operational amplifier, the inverting input end of the second operational amplifier is connected with the non-inverting input end of the second operational amplifier, and the output end of the second operational amplifier is respectively connected with the T-shaped longitudinal ends of the T-shaped low-pass filter and the T-shaped high-pass filter. The third operational amplifier U1C introduces positive feedback through the feedback circuit I, the second operational amplifier U1B feeds back the output signal of the third operational amplifier U1C to the longitudinal end of the double-T-shaped RC filter to form bootstrap, so that the stop band of the trap is narrowed, the filtering effect is improved, and the second operational amplifier 1B serves as a voltage follower. The third operational amplifier provides both the gain of the feedback circuit I and the isolation of the dual T-type RC filter.

The T-shaped high-pass filter comprises a capacitor C3, a capacitor C5 and a resistor R5, one end of the capacitor C3 is connected with the output end of the first operational amplifier, the other end of the capacitor C3 is respectively connected with one end of the capacitor C5 and one end of the resistor R5, the other end of the capacitor C5 is connected with the non-inverting input end of the third operational amplifier, and the other end of the resistor R5 is connected with the output end of the second operational amplifier. The capacitor C3, the capacitor C5 and the resistor R5 form a typical T-shaped RC high-pass filter circuit, and the function of the filter circuit is to pass signals with the frequency of more than 50 Hz. The T-shaped low-pass filter comprises a resistor R4, a resistor R6 and a capacitor C4, wherein one end of the resistor R4 is connected with one end of the capacitor C3, the other end of the resistor R4 is respectively connected with one end of the resistor R6 and one end of the capacitor C4, the other end of the resistor R6 is connected with the non-inverting input end of the third operational amplifier, and the other end of the capacitor C4 is connected with the output end of the second operational amplifier; resistor R4, resistor R6 and capacitor C4 form a typical T-type RC low-pass filter circuit, and are used for enabling signals below 50Hz to pass. The capacitance relationship of the capacitor is c3=c5=c4/2, and the resistance relationship of the resistor is r4=r6=2r5.

The feedback circuit I comprises a resistor R7 and a resistor R8, one end of the resistor R7 is connected with the output end of the third operational amplifier, the other end of the resistor R7 is respectively connected with one end of the resistor R8 and the non-inverting input end of the second operational amplifier, and the other end of the resistor R8 is grounded. The resistor R7 and the resistor R8 are feedback resistors, and the quality factor of the filter can be improved by changing the voltage division ratio of the feedback resistors.

As shown in fig. 4, the low-pass filter includes a fourth operational amplifier U1D and a first digital potentiometer RP1, the non-inverting input terminal of the fourth operational amplifier is connected to the reference voltage source Vref, the inverting input terminal of the fourth operational amplifier is connected to one end of a resistor R9 and one end of a capacitor C7, the other end of the resistor R9 is connected to the output terminal of the third operational amplifier of the trap, the other end of the capacitor C7 is connected to the output terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is connected to the input terminal of the high-pass filter; the first digital potentiometer is connected in parallel with two ends of the capacitor C7. The first digital potentiometer is used as a feedback resistor of the fourth operational amplifier and is respectively connected with the output end and the inverting input end of the fourth operational amplifier. The resistor R9 is an input resistor of the operational amplifier U1D, the gain of the operational amplifier can be adjusted through the resistance ratio of the resistor and the digital potentiometer, and the capacitor C7 is used for forming a low-pass filter circuit with the resistor to filter high-frequency signals.

The cut-off frequency of the low-pass filter is

Passband voltage amplification of

Wherein RP1 is the resistance of the first digital potentiometer. The passband cut-off frequency of the low-pass filter is adjusted by adjusting the resistance RP1 of the first digital potentiometer through micro-processing; when the resistance RP1 of the first digital potentiometer is changed, the passband magnification of the low-pass filter is also changed.

As shown in fig. 5, the high-pass filter includes a fifth operational amplifier U2A, a second digital potentiometer and a third digital potentiometer, wherein the non-inverting input end of the fifth operational amplifier is connected to a reference voltage source, the inverting input end of the fifth operational amplifier is respectively connected to one end of the capacitor C10 and one end of the second digital potentiometer, the other end of the second digital potentiometer is connected to the output end of the fifth operational amplifier, and the output end of the fifth operational amplifier is connected to the input end of the programmable gain amplifier; the other end of the capacitor C10 is respectively connected with one end of the capacitor C8, one end of the capacitor C9 and one end of the third digital potentiometer, the other end of the capacitor C8 is connected with the output end of the fourth operational amplifier, one end of the capacitor C9 is connected with the output end of the fifth operational amplifier, and the other end of the third digital potentiometer is grounded; the capacitor C8, the digital potentiometer RP3, the capacitor C10 and the digital potentiometer RP2 respectively form a first-order RC high-pass filter circuit, and the two RC high-pass filter circuits, the capacitor C9 and the operational amplifier U2A form a second-order infinite gain multipath feedback type high-pass filter. The 4 th pin of the fifth operational amplifier U2A is connected to the voltage source VCC and one end of the capacitor C11 respectively, the other end of the capacitor C11 is grounded, and the 11 th pin is grounded. The capacitor C11 is a power supply filter capacitor and is used for filtering power supply signal interference.

And the resistance values of the second digital potentiometer and the third digital potentiometer are kept in a fixed proportional relation. Electric powerThe capacitance relationship of the capacitor is c8=c10=2c9, and the resistance relationship of the second digital potentiometer and the third digital potentiometer is rp2= 6.25RP3, so that when one of the resistances is adjusted, the other must be simultaneously and equally adjusted. The pass band voltage amplification factor of the high pass filter is

Cut-off frequency is +.>

Wherein RP2 is the resistance of the second digital potentiometer, and RP3 is the resistance of the third digital potentiometer. The microprocessor is used for adjusting the pass band cut-off frequency of the high-pass filter by simultaneously and proportionally adjusting the resistance RP2 of the second digital potentiometer and the resistance RP3 of the third digital potentiometer, and the pass band amplification factor of the pass band cut-off frequency is not changed.

As shown in fig. 6, the programmable gain amplifier includes a programmable gain amplifier chip U3, where the programmable gain amplifier chip U3 is internally provided with a front operational amplifier and a programmable gain operational amplifier, a 5 th pin of the programmable gain amplifier chip U3 is an inverting input end of the front operational amplifier, a 6 th pin is a non-inverting input end of the front operational amplifier, a 4 th pin is an output end of the front operational amplifier, a 3 rd pin is an inverting input end of the programmable gain operational amplifier, a 2 nd pin is a non-inverting input end of the programmable gain operational amplifier, and a 16 th pin is an output end of the programmable gain operational amplifier. The inverting input end of the front-end operational amplifier is connected with the output signal of the high-pass filter through an input resistor R10 and a DC blocking capacitor C12, the non-inverting input end of the front-end operational amplifier is connected with a reference voltage source, the output end of the front-end operational amplifier is connected with the inverting input end of the front-end operational amplifier through a feedback resistor R12, the inverting input end of the programmable gain operational amplifier is connected with the output end of the front-end operational amplifier, the homodromous input end of the programmable gain operational amplifier is connected with the reference voltage source, and the output end of the programmable gain operational amplifier is connected with the microprocessor through a resistor R17; the resistor R17 is a limiting resistor, so that the input current of the microprocessor is prevented from being excessively large, and if current limiting is not needed, the resistance value is set to be 0. The GND pin of the programmable gain amplifying chip U3 is grounded, the programmable gain amplifying chip U3 is internally provided with a front-end operational amplifier and a programmable gain operational amplifier for two-stage amplification, the front-end operational amplifier can adjust gain through the ratio of a feedback resistor R12 and an input resistor R10, the programmable gain operational amplifier can adjust gain through three gear adjusting interfaces G0, G1 and G2, the gain represented by each gear of the programmable gain operational amplifier is fixed, the gain of the front-end operational amplifier can be adjusted through resistance, the gain of the front-end operational amplifier is multiplied by the gain of the programmable gain operational amplifier to be the overall gain of the programmable gain amplifying chip U3, and the output end of the front-end operational amplifier needs to be connected to the reverse input end of the programmable gain operational amplifier. The SHDN pin of the programmable gain amplification chip U3 is grounded through a resistor R18, SHDN is abbreviated as shutdown, the SHDN pin is connected with a high level to stop the chip, the SHDN pin is connected with a low level to enable the chip, and the resistor R18 is used for keeping the logic level of the SHDN pin stable. The VCC+PRE pin of the programmable gain amplification chip U3, the power VCC+ connected with the VCC+pin, the VCC-PRE pin and the power VCC-connected with the VCC-pin are respectively connected with the power VCC+ through a resistor R19 and grounded through a capacitor C15, and the resistor R19 and the capacitor C15 form an RC filter for filtering power signal interference. The VL pin is connected with a power supply VCC-through a resistor R21 and grounded through a capacitor C17, and the resistor R21 and the capacitor C17 form an RC filter to filter power supply signal interference.

The programmable gain amplification chip is provided with three gear adjusting interfaces, and the gear adjusting interfaces are connected with the microprocessor through an adjusting circuit and adjust gain according to commands of the microprocessor. The signal amplification factor of the programmable gain amplifier is

Gain values for different gain stages. The adjusting circuit comprises a resistor R13, a resistor R14 and a capacitor C13 which are connected with the first gear adjusting interface, a resistor R15, a resistor R16 and a capacitor C14 which are connected with the second gear adjusting interface, and a resistor R20, a resistor R22 and a capacitor C16 which are connected with the third gear adjusting interface; the first gear adjusting interface is respectively connected with one end of the resistor R13 and one end of the resistor R14The end is connected with one end of a capacitor C13, the other end of a resistor R13 and the other end of the capacitor C13 are grounded, and the other end of a resistor R14 is connected with a microprocessor; the second gear adjusting interface is respectively connected with one end of a resistor R15, one end of a resistor R16 and one end of a capacitor C14, the other end of the resistor R15 and the other end of the capacitor C14 are grounded, and the other end of the resistor R16 is connected with a microprocessor; the third gear adjusting interface is respectively connected with one end of a resistor R20, one end of a resistor R21 and one end of a capacitor C16, the other end of the resistor R20 and the other end of the capacitor C16 are grounded, and the other end of the resistor R22 is connected with a microprocessor. The microprocessor controls the gain setting of the programmable gain amplifier according to whether the amplitude of the sampling signal needs to be adjusted or not. The gear adjusting interfaces G0, G1 and G2 are respectively grounded through the resistor R13, the resistor R15 and the resistor R20, so that the programmable gain amplifying chip works at the logic level 000 gears by default, and the condition of uncertain gain state can not occur; the capacitor C13, the capacitor C14, the capacitor C16, the resistor R14, the resistor R16 and the resistor R22 respectively filter and limit the output signals of the microprocessor.

The programmable gain amplifier sets the gain according to the output level of the microprocessor, and the input level of each gear adjusting interface can be 0 or 1, for example, the levels of three gear adjusting interfaces of G0, G1 and G2 are 000, 001, 010, 011 or 100 respectively, and the like, which correspond to the gain settings of different gears from low to high respectively.

The gear of the programmable gain amplifier is set as a middle gear by default, when the passband of the band-pass filter is changed by changing and adjusting the resistance of the digital potentiometer, the signal gain of the low-pass filter is changed along with the change, and according to the passband voltage amplification calculation formula of the low-pass filter, the signal gain of the low-pass filter is changed into the ratio of the resistance after the change of the digital potentiometer to the resistance before the change, if the ratio is greater than 1, the programmable gain amplifier is required to be set as a lower gear than the original one, and if the ratio is less than 1, the programmable gain amplifier is required to be set as a higher gear than the original one, so that the change of the overall gain of the signal is compensated.

As shown in fig. 7, the first digital potentiometer, the second digital potentiometer and the third digital potentiometer all include a digital potentiometer chip, the VDD pin of the digital potentiometer chip is connected to a voltage source, the VSS pin of the digital potentiometer chip is grounded, the SCL pin and the SDA pin of the digital potentiometer chip are both connected to a microprocessor, the SCL pin is connected to the voltage source through a resistor R36, the SDA pin is connected to the voltage source through a resistor R37, SCL and SDA are I2C interfaces, and the resistor R36 and the resistor R37 are pull-up resistors of the I2C interfaces, because I2C communication is an open-drain output, only low level can be output, but not high level can be output, so that high level in the I2C communication process needs to be realized through an external pull-up resistor. The W pin and the B pin of the digital potentiometer chip are used as input ends and output ends respectively connected with the low-pass filter or the high-pass filter. The microprocessor provides clock signals through the 3 rd pin to enable the digital potentiometer to work according to time sequence, sends control instructions through the 4 th pin to enable the digital potentiometer to work in different resistance value gears, the 5 th pin and the 6 th pin are connected into a low-pass filter or a high-pass filter circuit, and pass band frequency or gain of the band-pass filter is adjusted according to the change of the resistance value between the 5 th pin and the 6 th pin.

The microprocessor is connected with the first digital potentiometer, the second digital potentiometer, the third digital potentiometer and the programmable gain amplifier, analyzes the water leakage condition according to the sampling signal, and judges whether to carry out gear adjustment on each digital potentiometer and the programmable gain amplifier.

Example 2

As shown in fig. 8, a noise signal processing method includes the following steps:

the piezoelectric sensor collects water leakage noise signals and converts sound wave signals into charge signals;

the charge amplifier amplifies weak charge signals generated by the piezoelectric sensor and converts the weak charge signals into voltage signals;

the wave trap filters 50Hz power frequency interference in the equipment;

the initial cut-off frequency of the low-pass filter of the band-pass filter is set to be 2.5KHz of the upper limit frequency of the water leakage noise signal, and noise signals above the cut-off frequency are filtered;

the initial cut-off frequency of a high-pass filter of the band-pass filter is set to be 50Hz, and noise signals below the cut-off frequency are filtered;

the programmable gain amplifier sets a default signal gain;

the microprocessor processes and analyzes the sampling signal and judges the water leakage condition.

The detection results of the water leakage condition are divided into four types: the signal amplitude abnormality, leakage, no leakage and suspected leakage are divided into two conditions of too small amplitude and too large amplitude, when the amplitude is too small, the difference between signal sampling values is too small, the analysis and judgment are not facilitated, and when the amplitude is too large, amplitude distortion can occur, and the signal shape is changed. When the signal amplitude is abnormal, the microprocessor adjusts the gear of the programmable gain amplifier to enable the signal amplitude to be at a proper position for sampling and analysis judgment, so that the problem that a water leakage noise signal is difficult to find out when noise is analyzed due to small discrimination of a sampling value of the microprocessor or misjudgment is caused by change of the signal shape is avoided, and the accuracy of a detection result is higher.

When the sampling analysis result of the microprocessor cannot determine whether leakage is suspected to occur, recording a signal frequency point of the suspected leakage, and taking the signal frequency point as a center frequency, the microprocessor adjusts a passband of a bandpass filter formed by the low-pass filter and the high-pass filter; when the low-pass filter generates gain change due to the adjustment of the cut-off frequency, synchronously adjusting the signal gain of the programmable gain amplifier to compensate; and further specifically analyzing the signal frequency points suspected of leakage, and judging whether leakage occurs or not.

The microprocessor performs frequency domain transformation on the acquired time domain signals, analyzes the frequency spectrum of the acquired signals, and judges whether water leakage or suspected water leakage occurs according to the frequency domain characteristics of the acquired signals. For example, the signal spectrum in the frequency range of 1.2KHz-1.5KHz shows that there may be a leakage signal in the frequency range, but because noise signals in other frequencies are too much to be confirmed, the intermediate value of 1.35KHz between 1.2KHz and 1.5KHz is taken as the center frequency, the bandwidth of the band-pass filter is set to be 1KHz, the cut-off frequency of the low-pass filter is 0.85KHz, the cut-off frequency of the high-pass filter is 1.85KHz, the gear positions of the digital potentiometer are respectively adjusted according to the cut-off frequencies of the low-pass filter and the high-pass filter, so that the low-pass filter and the high-pass filter respectively reach the set cut-off frequency values, and the programmable gain amplifier is adjusted to compensate gain variation. After the adjustment is finished, the signals are collected again for amplification and filtering, more interference noise signals are filtered due to narrowing of the passband of the bandpass filter, the signal to noise ratio is improved, and the microprocessor can more easily confirm whether leakage occurs or not when carrying out spectrum analysis on the sampled signals.

When the sampling analysis result of the microprocessor can judge leakage or no leakage, the analysis result is displayed, and the passband frequency of the bandpass filter and the gain setting of each stage of circuit are kept unchanged.

When the leakage is suspected, the low-pass filter adjusts the low-pass cut-off frequency by taking the signal frequency point suspected to be leaked as the center frequency; and the high-pass filter adjusts the high-pass cutoff frequency by taking the suspected leaked signal frequency point as the center frequency. The center frequency is a median of the low-pass cut-off frequency and the high-pass cut-off frequency.

According to the characteristics of each stage of circuit, the signal gains of the charge amplifier and the high-pass filter are fixed gains, and the signal gains of the low-pass filter and the programmable gain amplifier are adjustable gains. When the initial signal gain of each stage of circuit is set, the initial gain of the programmable gain amplifier is set in a middle gear and can be adjusted upwards or downwards according to actual conditions according to the actual water leakage noise signal amplitude range.

The initial passband frequency range of the bandpass filter is consistent with the frequency range of the water leakage noise signal, the initial low-pass cutoff frequency is the upper limit frequency of the water leakage noise signal, and the initial high-pass cutoff frequency is the lower limit frequency of the water leakage noise signal. The frequency range of the water leakage noise signal is usually 50Hz-2.5KHz, and when the signal is sampled and analyzed, the signal in the whole frequency range is sampled and analyzed firstly, because the leakage signal can be any frequency signal in the range of 50Hz-2.5KHz, the initial setting of the filter is consistent with the frequency range, and the leakage of the signal in a certain frequency is prevented from being detected. During each detection, firstly, analysis is carried out in the whole frequency range of the water leakage noise signal, and when a suspected leakage frequency point appears or a signal in a certain frequency section is suspected to have a leakage signal, specific analysis of a passband is changed aiming at the certain frequency point.

Other structures and circuit principles are the same as those of embodiment 1.

The foregoing description of the preferred embodiments of the utility model is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the utility model.

Claims (7)

1. The noise signal processing circuit is characterized by comprising a charge amplifier, a trap, a band-pass filter, a programmable gain amplifier and a microprocessor which are sequentially connected, wherein a digital potentiometer is arranged in the band-pass filter, and the microprocessor is respectively connected with the digital potentiometer and a gear of the programmable gain amplifier; the charge amplifier is used for amplifying a charge signal generated by the piezoelectric sensor and converting the charge signal into a voltage signal; the wave trap is used for filtering 50Hz power frequency interference in equipment; the band-pass filter adjusts a passband by changing the resistance gear of the digital potentiometer, filters and amplifies noise signals; the programmable gain amplifier is used for adjusting the amplitude gain of the noise signal and compensating the gain change when the passband of the band-pass filter is changed; and the microprocessor adjusts the gears of the digital potentiometer and the programmable gain amplifier according to the sampling signals, adjusts the signal gain and the passband of the bandpass filter, and analyzes whether water leakage occurs.

2. The noise signal processing circuit of claim 1, wherein the band pass filter comprises a low pass filter and a high pass filter, an input of the low pass filter is connected to the trap, an output of the low pass filter is connected to an input of the high pass filter, and an output of the high pass filter is connected to the programmable gain amplifier; and digital potentiometers are arranged in the low-pass filter and the high-pass filter, and the gear of the digital potentiometers is connected with the microprocessor.

3. The noise signal processing circuit according to claim 1 or 2, wherein the charge amplifier comprises a first operational amplifier, a non-inverting input terminal of the first operational amplifier is connected with a reference voltage source, an inverting input terminal of the first operational amplifier is connected with a positive electrode of the piezoelectric sensor through a capacitor C1, an inverting input terminal of the first operational amplifier is connected with an output terminal of the first operational amplifier through a connection circuit, and an output terminal of the first operational amplifier is connected with an input terminal of the trap; the connecting circuit comprises a capacitor C2, a resistor R1, a resistor R2 and a resistor R3, wherein the inverting input end of the first operational amplifier is respectively connected with one end of the capacitor C2 and one end of the resistor R2, the other end of the capacitor C2 is connected with the output end of the first operational amplifier, the other end of the resistor R2 is respectively connected with one end of the resistor R1 and one end of the resistor R3, the other end of the resistor R1 is connected with a reference voltage source, and the other end of the resistor R3 is connected with the output end of the first operational amplifier.

4. A noise signal processing circuit according to claim 3, wherein the trap comprises a double-T-shaped RC filter, a second operational amplifier and a third operational amplifier, the double-T-shaped RC filter comprises a T-shaped low-pass filter and a T-shaped high-pass filter which are connected in parallel, one ends of the T-shaped transverse ends of the T-shaped low-pass filter and the T-shaped high-pass filter are connected with the output end of the first operational amplifier of the charge amplifier, the other ends of the T-shaped transverse ends of the T-shaped low-pass filter and the T-shaped high-pass filter are connected with the non-inverting input end of the third operational amplifier, the inverting input end of the third operational amplifier is connected with the output end of the third operational amplifier, the output end of the third operational amplifier is connected with the input end of the low-pass filter of the band-pass filter and the non-inverting input end of the feedback circuit I of the second operational amplifier, and the output end of the second operational amplifier is connected with the T-shaped longitudinal ends of the T-shaped low-pass filter and the T-shaped high-pass filter, respectively.

5. The noise signal processing circuit according to claim 4, wherein the T-type high-pass filter comprises a capacitor C3, a capacitor C5 and a resistor R5, one end of the capacitor C3 is connected to the output terminal of the first operational amplifier, the other end of the capacitor C3 is connected to one end of the capacitor C5 and one end of the resistor R5, the other end of the capacitor C5 is connected to the non-inverting input terminal of the third operational amplifier, and the other end of the resistor R5 is connected to the output terminal of the second operational amplifier; the T-shaped low-pass filter comprises a resistor R4, a resistor R6 and a capacitor C4, wherein one end of the resistor R4 is connected with one end of the capacitor C3, the other end of the resistor R4 is respectively connected with one end of the resistor R6 and one end of the capacitor C4, the other end of the resistor R6 is connected with the non-inverting input end of the third operational amplifier, and the other end of the capacitor C4 is connected with the output end of the second operational amplifier; the feedback circuit I comprises a resistor R7 and a resistor R8, one end of the resistor R7 is connected with the output end of the third operational amplifier, the other end of the resistor R7 is respectively connected with one end of the resistor R8 and the non-inverting input end of the second operational amplifier, and the other end of the resistor R8 is grounded.

6. The noise signal processing circuit according to any one of claims 2, 4 or 5, wherein the low-pass filter comprises a fourth operational amplifier and a first digital potentiometer, the non-inverting input terminal of the fourth operational amplifier is connected to a reference voltage source, the inverting input terminal of the fourth operational amplifier is connected to one end of a resistor R9 and one end of a capacitor C7, respectively, the other end of the resistor R9 is connected to the output terminal of the third operational amplifier of the trap, the other end of the capacitor C7 is connected to the output terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is connected to the input terminal of the high-pass filter; the first digital potentiometer is connected in parallel with two ends of the capacitor C7; the high-pass filter comprises a fifth operational amplifier, a second digital potentiometer and a third digital potentiometer, wherein the non-inverting input end of the fifth operational amplifier is connected with a reference voltage source, the inverting input end of the fifth operational amplifier is respectively connected with one end of a capacitor C10 and one end of the second digital potentiometer, the other end of the second digital potentiometer is connected with the output end of the fifth operational amplifier, and the output end of the fifth operational amplifier is connected with the input end of the programmable gain amplifier; the other end of the capacitor C10 is respectively connected with one end of the capacitor C8, one end of the capacitor C9 and one end of the third digital potentiometer, the other end of the capacitor C8 is connected with the output end of the fourth operational amplifier, the other end of the capacitor C9 is connected with the output end of the fifth operational amplifier, and the other end of the third digital potentiometer is grounded; and the resistance values of the second digital potentiometer and the third digital potentiometer are kept in a fixed proportional relation.

7. The noise signal processing circuit according to claim 6, wherein the programmable gain amplifier comprises a programmable gain amplification chip, wherein a front-end operational amplifier and a programmable gain operational amplifier are arranged in the programmable gain amplification chip, an inverting input end of the front-end operational amplifier is connected with an output signal of the high-pass filter through an input resistor R10 and a DC blocking capacitor C12, a non-inverting input end of the front-end operational amplifier is connected with a reference voltage source, an output end of the front-end operational amplifier is connected with an inverting input end of the front-end operational amplifier through a feedback resistor R12, an inverting input end of the programmable gain operational amplifier is connected with an output end of the front-end operational amplifier, a non-inverting input end of the programmable gain operational amplifier is connected with the reference voltage source, and an output end of the programmable gain operational amplifier is connected with the microprocessor through a resistor R17;

the programmable gain amplification chip is provided with three gear adjusting interfaces, and the gear adjusting interfaces are connected with the microprocessor through an adjusting circuit and adjust gain according to commands of the microprocessor; the adjusting circuit comprises a resistor R13, a resistor R14 and a capacitor C13 which are connected with the first gear adjusting interface, a resistor R15, a resistor R16 and a capacitor C14 which are connected with the second gear adjusting interface, and a resistor R20, a resistor R22 and a capacitor C16 which are connected with the third gear adjusting interface; the first gear adjusting interface is respectively connected with one end of a resistor R13, one end of a resistor R14 and one end of a capacitor C13, the other end of the resistor R13 and the other end of the capacitor C13 are grounded, and the other end of the resistor R14 is connected with a microprocessor; the second gear adjusting interface is respectively connected with one end of a resistor R15, one end of a resistor R16 and one end of a capacitor C14, the other end of the resistor R15 and the other end of the capacitor C14 are grounded, and the other end of the resistor R16 is connected with a microprocessor; the third gear adjusting interface is respectively connected with one end of a resistor R20, one end of a resistor R21 and one end of a capacitor C16, the other end of the resistor R20 and the other end of the capacitor C16 are grounded, and the other end of the resistor R22 is connected with a microprocessor;

The first digital potentiometer, the second digital potentiometer and the third digital potentiometer comprise digital potentiometer chips, VDD pins of the digital potentiometer chips are connected with a voltage source, VSS pins of the digital potentiometer chips are grounded, SCL pins and SDA pins of the digital potentiometer chips are connected with a microprocessor, SCL pins are connected with the voltage source through resistors R36, SDA pins are connected with the voltage source through resistors R37, W pins of the digital potentiometer chips are used as input ends, and B pins are used as output ends and are respectively connected with a low-pass filter or a high-pass filter.

Images