阅读说明：本技术 一种用于天然气泄漏激光检测系统的多源噪声抑制电路 (Multi-source noise suppression circuit for natural gas leakage laser detection system ) 是由 王明吉 梁涛 李栋 李玉爽 吕妍 王迪 于 2019-10-12 设计创作，主要内容包括：一种用于天然气泄漏激光检测系统的多源噪声抑制电路,涉及检测设备技术领域,它包括电源电路、偏置电路、运放电路和滤波电路,电源电路和偏置电路分别与运放电路连接,运放电路与滤波电路连接。本用于天然气泄漏激光检测系统的多源噪声抑制电路采用的电源电路采用RC有源滤波形式可以直接过滤直流电源里的杂波,并为电路中运放提供稳定输出电压；运放单电路采用运放反馈电阻并联电容的构造方案,实现I/V转换的同时还可以减少转换损失；滤波电路采用窄带滤波法,既提高电路整体信噪比同时也保障了后续数据的准确度。(The utility model provides a multisource noise suppression circuit for natural gas leakage laser detecting system, relates to check out test set technical field, and it includes power supply circuit, biasing circuit, operational amplifier circuit and filter circuit, and power supply circuit and biasing circuit are connected with the operational amplifier circuit respectively, and the operational amplifier circuit is connected with filter circuit. The power circuit adopted by the multisource noise suppression circuit for the natural gas leakage laser detection system adopts an RC active filtering mode, can directly filter clutter in a direct current power supply, and provides stable output voltage for an operational amplifier in the circuit; the operational amplifier single circuit adopts a structural scheme that an operational amplifier feedback resistor is connected with a capacitor in parallel, so that the I/V conversion is realized, and the conversion loss can be reduced; the filter circuit adopts a narrow-band filtering method, so that the integral signal-to-noise ratio of the circuit is improved, and the accuracy of subsequent data is guaranteed.)

1. The utility model provides a multisource noise suppression circuit for natural gas leakage laser detecting system which characterized in that: the power supply circuit (1) and the bias circuit (2) are respectively connected with the operational amplifier circuit (3), and the operational amplifier circuit (3) is connected with the filter circuit (4).

2. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, wherein: the power supply circuit (1) comprises a first power supply circuit (11) and a second power supply circuit (12), and the first power supply circuit (11) and the second power supply circuit (12) are respectively connected with the operational amplifier circuit (3).

3. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 2, wherein: the power supply circuit I (11) is constructed by a power supply, a capacitor, a resistor and an NPN type transistor 2N 6727; the second power circuit (12) is constructed by a power supply, a capacitor, a resistor and an NPN type transistor 2N 6714.

4. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, wherein: the power supply circuit (1) adopts an RC active filtering form.

5. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, wherein: the bias circuit (2) is constructed by a power supply, a voltage, a capacitor, a resistor, a rheostat and an NPN transistor 2N 2222.

6. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1 or 5, wherein: the bias circuit (2) adopts an NPN type transistor 2N2222 to build a transistor follower circuit, and capacitors are added to the base stage and the emitter of the transistor to form a low-pass filter circuit.

7. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, wherein: the operational amplifier circuit (3) comprises a first-stage operational amplifier circuit (31) and a second-stage operational amplifier circuit (32), and the first-stage operational amplifier circuit (31) and the second-stage operational amplifier circuit (32) are connected in a resistance-capacitance coupling mode.

8. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 6, wherein: the first-stage operational amplifier circuit (31) is an I/V conversion circuit, and the first-stage operational amplifier circuit (31) is constructed by a power supply, a capacitor, a resistor and an ultra-precise high-speed low-noise operational amplifier LT 1028; the second-stage operational amplifier circuit (32) is constructed by a power supply, a resistor, a rheostat and a low-noise and low-temperature-drift operational amplifier OP37, wherein the resistor and the rheostat form a T-shaped feedback network with lower feedback resistance.

9. The multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, wherein: the filter circuit (4) adopts a narrow-band filtering method, the filter circuit (4) is constructed by a power supply, a capacitor, a resistor and two operational amplifiers OP37, the two operational amplifiers OP37 are respectively constructed into a second-order high-pass filter and a second-order low-pass filter, and the second-order high-pass filter and the second-order low-pass filter are connected in series to form a band-pass filter.

10. The use method of the multi-source noise suppression circuit for the natural gas leakage laser detection system according to claim 1, is characterized in that: the working process is as follows:

the detector receives the interference light signal and then completes signal conversion;

the bias circuit (2) provides bias voltage required by normal operation for the detector;

the operational amplifier circuit (3) realizes I/V conversion and signal amplification, summarizes the I/V conversion process, and reduces the influence of noise on the circuit by selecting a mode of connecting a feedback resistor in parallel with a compensation capacitor, thereby improving the integral signal-to-noise ratio of the circuit;

in the second-stage operational amplifier circuit (32), a T-shaped feedback network with high voltage gain and low feedback resistance is adopted to improve the structure of the circuit so as to avoid introducing larger thermal noise;

the filter circuit (4) adopts a narrow-band filtering method, so that the overall signal-to-noise ratio of the circuit is further improved, and the accuracy of subsequent data acquisition is guaranteed.

The technical field is as follows:

the invention relates to the technical field of detection equipment, in particular to a multi-source noise suppression circuit for a natural gas leakage laser detection system.

Background art:

in recent years, gas poisoning and natural gas explosion accidents frequently occur in various parts of China, so that people pay more and more attention to how to realize quick and accurate detection of leaked natural gas. With the development of technologies such as semiconductor lasers, sensors and the like, the natural gas detection technology has a good development prospect. However, in the actual detection process, the problem of measuring signals in the micro-millivolt range is often encountered, and these detected signals are very weak and easily submerged in noise, so that the detected signals cannot be accurately measured, and thus a weak signal detection technology is generated. The weak signal detection is to extract useful signals from noise by using modern electronics and a signal processing method, and a low-noise preamplifier is a very important component of the weak signal detection and is commonly used at the front end of a receiving system, so that the noise interference is inhibited while the received signals are amplified, and the system accuracy is improved. If a high-performance low-noise amplifier is connected to the front end of the receiving system, and the gain of the low-noise amplifier is large enough, the noise of the subsequent circuit can be suppressed, and the noise of the whole receiving system is mainly determined by the noise of the amplifier. Therefore, the invention mainly aims to design a multi-source noise suppression circuit, so that the multi-source noise suppression circuit achieves a certain amplification factor and has better anti-interference capability.

The invention content is as follows:

the invention aims to overcome the defects of the prior art and provides the multisource noise suppression circuit for the natural gas leakage laser detection system, which has the advantages of compact design structure, good real-time performance, quick response, high reliability, good stability and the like.

In order to solve the problems existing in the background technology, the invention adopts the following technical scheme: the power supply circuit and the bias circuit are respectively connected with the operational amplifier circuit, and the operational amplifier circuit is connected with the filter circuit.

The power supply circuit comprises a first power supply circuit and a second power supply circuit, and the first power supply circuit and the second power supply circuit are respectively connected with the operational amplifier circuit.

The first power supply circuit is constructed by a power supply, a capacitor, a resistor and an NPN type transistor 2N 6727; the second power supply circuit is constructed by a power supply, a capacitor, a resistor and an NPN transistor 2N 6714.

The power circuit adopts an RC active filtering form.

The bias circuit is constructed by a power supply, a voltage, a capacitor, a resistor, a rheostat and an NPN transistor 2N 2222.

The bias circuit adopts an NPN type transistor 2N2222 to build a emitter follower circuit, and capacitors are added to a base stage and an emitter of the transistor to form a low-pass filter circuit.

The operational amplifier circuit comprises a first-stage operational amplifier circuit and a second-stage operational amplifier circuit, and the first-stage operational amplifier circuit and the second-stage operational amplifier circuit are connected in a resistance-capacitance coupling mode.

The first-stage operational amplifier circuit is an I/V conversion circuit and is constructed by a power supply, a capacitor, a resistor and an ultra-precise high-speed low-noise operational amplifier LT 1028; the second-stage operational amplifier circuit is constructed by a power supply, a resistor, a rheostat and a low-noise and low-temperature-drift operational amplifier OP37, wherein the resistor and the rheostat form a T-shaped feedback network with lower feedback resistance.

The filter circuit adopts a narrow-band filtering method, the filter circuit is constructed by a power supply, a capacitor, a resistor and two operational amplifiers OP37, the two operational amplifiers OP37 are respectively constructed into a second-order high-pass filter and a second-order low-pass filter, and the second-order high-pass filter and the second-order low-pass filter are connected in series to form a band-pass filter.

The working process is as follows:

1) the detector receives the interference light signal and then completes signal conversion;

2) the bias circuit provides bias voltage required by normal operation for the detector;

3) the operational amplifier circuit realizes I/V conversion and signal amplification, the I/V conversion process is summarized, the influence of noise on the circuit is reduced by selecting a mode of connecting a feedback resistor in parallel with a compensation capacitor, and the integral signal-to-noise ratio of the circuit is improved;

4) in the second-stage operational amplifier circuit, a T-shaped feedback network with high voltage gain and low feedback resistance is adopted to improve the structure of the circuit so as to avoid introducing larger thermal noise;

5) the filter circuit adopts a narrow-band filtering method, so that the overall signal-to-noise ratio of the circuit is further improved, and the accuracy of subsequent data acquisition is guaranteed.

The invention has the beneficial effects that:

1) the power circuit adopts an RC active filtering form to directly filter clutter in the direct current power supply and provide stable output voltage for an operational amplifier in the circuit;

2) the operational amplifier single circuit adopts a structural scheme that an operational amplifier feedback resistor is connected with a capacitor in parallel, so that the I/V conversion is realized, and the conversion loss can be reduced;

3) the filter circuit adopts a narrow-band filtering method, so that the integral signal-to-noise ratio of the circuit is improved, and the accuracy of subsequent data is guaranteed.

Description of the drawings:

FIG. 1 is an overall circuit diagram of the present invention;

FIG. 2 is a circuit diagram of a power supply circuit of the present invention;

FIG. 3 is a second circuit diagram of the power circuit of the present invention;

FIG. 4 is a circuit diagram of the bias circuit of the present invention;

FIG. 5 is a circuit diagram of the operational amplifier of the present invention;

FIG. 6 is a circuit diagram of a filter circuit of the present invention;

fig. 7 is a flow chart of the present invention.

The specific implementation mode is as follows:

referring to the drawings, the present invention specifically adopts the following embodiments: the power supply circuit 1 and the bias circuit 2 are respectively connected with the operational amplifier circuit 3, and the operational amplifier circuit 3 is connected with the filter circuit 4. The power supply circuit 1 comprises a first power supply circuit 11 and a second power supply circuit 12, and the first power supply circuit 11 and the second power supply circuit 12 are respectively connected with the operational amplifier circuit 3. The power circuit I11 is constructed by a power supply, a capacitor, a resistor and an NPN type transistor 2N 6727; the second power circuit 12 is constructed by a power supply, a capacitor, a resistor and an NPN transistor 2N 6714. The power supply circuit 1 adopts an RC active filtering form. The bias circuit 2 is constructed by a power supply, a voltage, a capacitor, a resistor, a rheostat and an NPN transistor 2N 2222. The bias circuit 2 adopts an NPN type transistor 2N2222 to build a transistor follower circuit, and capacitors are added to the base stage and the emitter of the transistor to form a low-pass filter circuit. The operational amplifier circuit 3 comprises a first-stage operational amplifier circuit 31 and a second-stage operational amplifier circuit 32, and the first-stage operational amplifier circuit 31 and the second-stage operational amplifier circuit 32 are connected in a resistance-capacitance coupling mode. The first-stage operational amplifier circuit 31 is an I/V conversion circuit, and the first-stage operational amplifier circuit 31 is constructed by a power supply, a capacitor, a resistor and an ultra-precise high-speed low-noise operational amplifier LT 1028; the second stage operational amplifier circuit 32 is constructed by a power supply, a resistor, a varistor and a low-noise and low-temperature-drift operational amplifier OP37, wherein the resistor and the varistor form a T-shaped feedback network with a low feedback resistance value. The filter circuit 4 adopts a narrow-band filtering method, the filter circuit 4 is constructed by a power supply, a capacitor, a resistor and two operational amplifiers OP37, the two operational amplifiers OP37 are respectively constructed into a second-order high-pass filter and a second-order low-pass filter, and the second-order high-pass filter and the second-order low-pass filter are connected in series to form a band-pass filter.

Referring to fig. 7, the workflow is as follows:

1) the detector receives the interference light signal and then completes signal conversion;

2) the bias circuit 2 provides bias voltage required by normal operation for the detector;

3) the operational amplifier circuit 3 realizes I/V conversion and signal amplification, summarizes the I/V conversion process, and reduces the influence of noise on the circuit by selecting a mode of connecting a feedback resistor in parallel with a compensation capacitor, thereby improving the integral signal-to-noise ratio of the circuit;

4) in the second-stage operational amplifier circuit 32, a T-type feedback network with high voltage gain and low feedback resistance is adopted to improve the structure of the circuit so as to avoid introducing large thermal noise;

5) the filter circuit 4 adopts a narrow-band filtering method, so that the overall signal-to-noise ratio of the circuit is further improved, and the accuracy of subsequent data acquisition is guaranteed.

Referring to fig. 2 and 3, the power circuit 1 adopts an RC active filtering form to directly filter out noise in the dc power supply and provide a stable output voltage for the operational amplifier in the circuit.

Referring to fig. 4, an NPN transistor 2N2222 having low power consumption, good current characteristics, and high gain is selected from the bias circuit 2, and a transistor emitter follower circuit is built to implement voltage following. And capacitors are added to the base level and the emitter of the transistor, so that power frequency interference can be reduced. The capacitors C1 and C2 and the resistor R3 at the base end of the transistor can filter out pulsating signals in the circuit, and the low-pass filter circuit formed by the capacitor C1 and the resistor R3 can eliminate high-frequency signal interference. The resistor R4 with a larger resistance value can make the transistor bias circuit 2 obtain a more stable static operating point, and the varistor P1 can adjust the operating state of the transistor to make it operate in the amplification region, thereby obtaining a more ideal output bias voltage.

Referring to fig. 5, the operational amplifier in the operational amplifier circuit 3 can be equivalent to an ideal noiseless operational amplifier with a noise voltage source connected in series at the non-inverting input terminal and a noise current source connected in series at the non-inverting input terminal. Equivalent noise voltage source produces noise

Equivalent noise current source generates noise

. Selecting an ultra-low noise high-speed operational amplifier LT1028 in an I/V conversion circuit, and then performing advanced compensation on the phase margin of the circuit by connecting an operational amplifier feedback resistor and a compensation capacitor in parallel and keeping the phase margin at 45-60 degrees to increaseAnd the stability of the circuit is large. The second-stage operational amplifier circuit 32 and the first-stage operational amplifier circuit 31 are coupled in a resistance-capacitance manner, so that not only are the static working points of the two-stage operational amplifiers not affected, but also a part of direct-current signals can be filtered to avoid the influence of the direct-current signals on the signals to be tested. The second-stage operational amplifier circuit 32 selects the low-noise low-temperature drift amplifier OP37, and adopts a T-type feedback network with high voltage gain and low feedback resistance to improve the structure of the feedback circuit, so as to solve the problem that a feedback resistor with large resistance must be introduced to obtain high gain, and the feedback resistor with too large resistance will bring large thermal noise and easily submerge the detected signal.

Referring to fig. 6, a narrow-band filtering method is adopted in the filtering circuit 4, and a method of broadband compression can not only improve the overall signal-to-noise ratio of the circuit, but also ensure the accuracy of subsequent data collection, so that an OP37 with low noise and strong load capacity is selected, a second-order high-pass filter and a second-order low-pass filter are respectively constructed, and then the two filters are connected in series to form a band-pass filter for filtering. The lower limit of the cut-off frequency of the band-pass filter is designed to be 70HZ, the upper limit frequency is designed to be 14HZ, and therefore the external noise can be restrained and the follow-up data acquisition is facilitated.

In summary, the multi-source noise suppression circuit for the natural gas leakage laser detection system adopts the RC active filtering mode to directly filter the clutter in the direct current power supply and provide stable output voltage for the operational amplifier in the circuit; the operational amplifier single circuit adopts a structural scheme that an operational amplifier feedback resistor is connected with a capacitor in parallel, so that the I/V conversion is realized, and the conversion loss can be reduced; the filter circuit adopts a narrow-band filtering method, so that the integral signal-to-noise ratio of the circuit is improved, and the accuracy of subsequent data is guaranteed.