阅读说明：本技术 一种用于音频信号测量的测量放大器 (Measuring amplifier for audio signal measurement ) 是由 李耀祖 张欢欢 阚雪珍 于 2020-11-04 设计创作，主要内容包括：本发明公开了一种用于音频信号测量的测量放大器,包括信号采集单元、信号处理单元、模数转换单元和微处理模块,信号采集单元、信号处理单元、模数转换单元和微处理模块依次相连,信号处理单元根据采集的音频信号的幅度大小,对微弱信号进行放大处理,对大信号进行衰减处理,对其余信号不予处理,再将经信号处理单元处理过的音频信号进行模数转换,然后发送至微处理模块计算获取采集的音频信号的实际测量值,扩大了测量放大器的测量精度和量程范围,能够满足微弱信号和大信号的测量要求,并降低了测量放大器自身的本底噪声。(The invention discloses a measuring amplifier for measuring audio signals, which comprises a signal acquisition unit, a signal processing unit, an analog-to-digital conversion unit and a micro-processing module, wherein the signal acquisition unit, the signal processing unit, the analog-to-digital conversion unit and the micro-processing module are sequentially connected, the signal processing unit is used for amplifying weak signals according to the amplitude of the acquired audio signals, attenuating large signals and not processing the rest signals, then performing analog-to-digital conversion on the audio signals processed by the signal processing unit and sending the audio signals to the micro-processing module for calculating and acquiring the actual measured value of the acquired audio signals, so that the measuring precision and the measuring range of the measuring amplifier are expanded, the measuring requirements of the weak signals and the large signals can be met, and the background noise of the measuring amplifier is reduced.)

1. The measuring amplifier for measuring the audio signals is characterized by comprising a signal acquisition unit, a signal processing unit, an analog-to-digital conversion unit and a micro-processing module, wherein the signal acquisition unit, the signal processing unit, the analog-to-digital conversion unit and the micro-processing module are sequentially connected, the signal acquisition unit is used for acquiring the audio signals, the signal processing unit is used for carrying out amplification processing and attenuation processing or non-processing on the audio signals according to the amplitude of the audio signals, the analog-to-digital conversion unit is used for converting the analog signals into digital signals, and the micro-processing module is used for calculating and obtaining actual measured values of the audio signals.

2. The measuring amplifier for audio signal measurement according to claim 1, wherein the signal processing unit comprises a signal relay A, a signal relay B, an attenuation circuit, an amplifying circuit, a relay driving circuit and a signal detection module, the input end of the signal detection module is connected to the signal acquisition unit, the output end of the signal detection module is connected to the input end of the relay driving circuit, the output end of the relay driving circuit is connected to the signal relay A and the signal relay B, the signal acquisition unit is connected to the signal relay B through the normally closed contact of the signal relay A, the signal acquisition unit is connected to the attenuation circuit through the normally open contact of the signal relay A, the attenuation circuit is connected to the signal relay B, the normally closed contact of the signal relay B is connected to the analog-to-digital conversion unit, and a normally open contact of the signal relay B is connected with the analog-to-digital conversion unit through an amplifying circuit.

3. The measurement amplifier for audio signal measurement according to claim 1 or 2, wherein the signal processing unit is connected to the analog-to-digital conversion unit through a program control unit, the program control unit comprises an amplifying circuit a and an amplifying circuit B, and the amplifying circuit a and the amplifying circuit B are arranged in parallel.

4. The measuring amplifier for audio signal measurement according to claim 2, wherein the relay driving circuit comprises a driving circuit A and a driving circuit B, the driving circuit A is used for driving the signal relay A, the driving circuit B is used for driving the signal relay B, the driving circuit A and the driving circuit B have the same structure, the driving circuit A comprises a relay power supply, a resistor R1, a triode Q1 and a diode D1, the base of the triode Q1 is connected with the signal detection module through a resistor R1, the emitter of the triode Q1 is grounded, the collector of the triode Q1 is connected with one end of the coil of the signal relay A, the other end of the coil of the signal relay A is connected with the relay power supply, the two sides of the coil of the signal relay A are connected with the diode D1 in parallel, the cathode of the diode D1 is connected with the relay power supply, and the anode of the diode D1 is connected with the collector of the triode Q1.

5. Measuring amplifier for audio signal measurement according to claim 1, the signal processing unit comprises a selection switch A, a selection switch B, an attenuation circuit, an amplification circuit, a switch driving module and a signal detection module, the input end of the signal detection module is connected with the signal acquisition unit, the output end of the signal detection module is connected with the input end of the switch driving module, the output end of the switch driving module is connected with a selection switch A and a selection switch B, the signal acquisition unit is connected with the selection switch B through a normally closed contact of the selection switch A, the signal acquisition unit is connected with an attenuation circuit through a normally open contact of a selection switch A, the attenuation circuit is connected with a selection switch B, and a normally closed contact of the selector switch B is connected with the analog-to-digital conversion unit, and a normally open contact of the selector switch B is connected with the analog-to-digital conversion unit through an amplifying circuit.

6. The measurement amplifier for audio signal measurement according to claim 5, wherein the switch driving module comprises a switch driving circuit A and a switch driving circuit B, the switch driving circuit A is used for driving the selection switch A, the switch driving circuit B is used for driving the selection switch B, the switch driving circuit A and the switch driving circuit B have the same structure, the switch driving circuit A comprises a power supply, a relay A, a resistor R3, a triode Q3, a diode D3 and a spring A, the base of the triode Q3 is connected with the signal detection module through a resistor R3, the emitter of the triode Q3 is grounded, the collector of the triode Q3 is connected with one end of the coil of the relay A, the other end of the coil of the relay A is connected with the power supply, the two sides of the coil of the relay A are connected with the diode D3 in parallel, the cathode of the diode D3 is connected with a power supply, the anode of the diode D3 is connected with the collector of the triode Q3, the normally open contact of the relay A is connected with one end of the spring A, the other end of the spring A is connected with the power supply, and the two ends of the spring A are respectively connected with the normally open contact and the normally closed contact of the selector switch A.

Technical Field

The invention relates to the technical field of measuring amplifiers, in particular to a measuring amplifier for measuring audio signals.

Background

The measuring amplifier can amplify and measure weak electric signals, generally has a large and adjustable amplification factor, and is widely applied to a detection system of the weak signals. The performance of the measuring amplifier mainly shows the following indexes: frequency characteristics, linearity, measurement accuracy, range, etc. The range of span depends on two factors: a lower measurement limit and an upper measurement limit. In general, an amplifier with a sufficiently large dynamic range is required to be able to measure both very weak small signals and large signals. The lower measurement limit depends mainly on the noise floor level of the circuitry itself. In most existing schemes or products, the scheme generally adopts a measurement mode of a signal amplification circuit and an analog-to-digital converter, has large background noise, small range and low precision, and cannot meet the measurement requirements of weak signals or large signals.

For example, chinese patent document CN106208977A discloses a "low-frequency and low-noise measurement amplifier" including four parts, namely, a noise matching transformer, a pre-stage amplification circuit, a band-pass filter, and a post-stage amplification circuit, which has the disadvantages of low measurement accuracy, small range of measurement, and failing to meet the measurement requirements of weak signals and large signals.

Disclosure of Invention

The invention mainly solves the technical problems that the original measuring amplifier has low measuring precision and small measuring range and can not meet the measuring requirements of weak signals and large signals; the signal processing unit amplifies weak signals according to the amplitude of collected audio signals, attenuates large signals, does not process other signals, and the micro-processing module calculates and obtains the actual measured value of the collected audio signals, so that the measurement precision and the range of the measurement amplifier are expanded, and the measurement requirements of the weak signals and the large signals can be met.

The technical problem of the invention is mainly solved by the following technical scheme: the device comprises a signal acquisition unit, a signal processing unit, an analog-to-digital conversion unit and a micro-processing module, wherein the signal acquisition unit, the signal processing unit, the analog-to-digital conversion unit and the micro-processing module are sequentially connected, the signal acquisition unit is used for acquiring audio signals, the signal processing unit is used for carrying out amplification processing and attenuation processing or non-processing on the audio signals according to the amplitude of the audio signals, the analog-to-digital conversion unit is used for converting the analog signals into digital signals, and the micro-processing module is used for calculating and acquiring actual measured values of the audio signals.

The signal processing unit amplifies the weak signal according to the amplitude of the acquired audio signal, attenuates the large signal, does not process the rest signals, performs analog-to-digital conversion on the audio signal processed by the signal processing unit, and sends the audio signal to the micro-processing module to calculate and acquire the actual measured value of the acquired audio signal, so that the measurement precision and the range of the measurement amplifier are enlarged, the measurement requirements of the weak signal and the large signal can be met, and the background noise of the measurement amplifier is reduced.

Preferably, the signal processing unit comprises a signal relay A, a signal relay B, an attenuation circuit, an amplification circuit, a relay driving circuit and a signal detection module, the input end of the signal detection module is connected with the signal acquisition unit, the output end of the signal detection module is connected with the input end of the relay drive circuit, the output end of the relay driving circuit is connected with a signal relay A and a signal relay B, the signal acquisition unit is connected with the signal relay B through the normally closed contact of the signal relay A, the signal acquisition unit is connected with an attenuation circuit through a normally open contact of a signal relay A, the attenuation circuit is connected with a signal relay B, and the normally closed contact of the signal relay B is connected with the analog-to-digital conversion unit, and the normally open contact of the signal relay B is connected with the analog-to-digital conversion unit through an amplifying circuit.

The measuring amplifier is divided into three ranges, namely a high range, a middle range and a low range, the high range is used for measuring signals with large amplitude, the middle range is used for measuring signals with moderate amplitude, the low range is used for measuring signals with weak amplitude, the signal detection module is used for detecting the amplitude of the acquired audio signals and selecting different ranges for signal processing according to the amplitude, when the high range is selected, the relay driving circuit drives a coil of the signal relay A to be electrified, the normally closed contact of the signal relay A is disconnected, the normally open contact is closed, the acquired audio signals enter the attenuation circuit through the signal relay A and then enter the analog-digital conversion module through the signal relay B; when the middle range is selected, the relay driving circuit does not drive the signal relay A and the signal relay B, and the collected audio signal enters the signal relay B through the signal relay A and then enters the analog-to-digital conversion module through the signal relay B; when selecting the low range, relay drive circuit drive signal relay B's coil circular telegram, signal relay B's normally closed contact disconnection, normally open contact is closed, and the audio signal of gathering enters into signal relay B through signal relay A, and rethread signal relay B enters into amplifier circuit, enters into analog-to-digital conversion module from amplifier circuit at last, can measure the range very big, the moderate and weak signal of range, has enlarged range.

Preferably, the signal processing unit is connected with the analog-to-digital conversion unit through a program control unit, the program control unit comprises an amplifying circuit A and an amplifying circuit B, and the amplifying circuit A and the amplifying circuit B are arranged in parallel.

The acquired audio signals are processed by the signal processing unit and then enter the amplifying circuit A and the amplifying circuit B at the same time, the amplifying times of the amplifying circuit A and the amplifying circuit B are different and are respectively connected with two independent channels of the analog-to-digital conversion module, and the data after analog-to-digital conversion are mixed and operated by the micro-processing module so as to improve the dynamic range of the circuit. The microprocessor automatically realizes the switching of the amplifying circuit A and the amplifying circuit B according to the amplitude of the input signal, and the whole switching process is realized by software, so that the response speed is high, and zero time delay can be realized. Through the two amplifying circuits with different amplification factors, the signal can be always kept in a range close to the full range of the analog-digital conversion module, the distortion of the signal is reduced, and the conversion precision is improved.

Preferably, the relay driving circuit comprises a driving circuit A and a driving circuit B, the driving circuit A is used for driving the signal relay A, the drive circuit B is used for driving the signal relay B, the structure of the drive circuit A is the same as that of the drive circuit B, the driving circuit A comprises a relay power supply, a resistor R1, a triode Q1 and a diode D1, the base electrode of the triode Q1 is connected with the signal detection module through a resistor R1, the emitter electrode of the triode Q1 is grounded, the collector of the triode Q1 is connected with one end of the coil of the signal relay A, the other end of the coil of the signal relay A is connected with the power supply of the relay, and two sides of the coil of the signal relay A are connected with a diode D1 in parallel, the cathode of the diode D1 is connected with a relay power supply, and the anode of the diode D1 is connected with the collector of the triode Q1.

Preferably, the signal processing unit comprises a selection switch A, a selection switch B, an attenuation circuit, an amplification circuit, a switch driving module and a signal detection module, wherein the input end of the signal detection module is connected with the signal acquisition unit, the output end of the signal detection module is connected with the input end of the switch driving module, the output end of the switch driving module is connected with the selection switch A and the selection switch B, the signal acquisition unit is connected with the selection switch B through a normally closed contact of the selection switch A, the signal acquisition unit is connected with the attenuation circuit through a normally open contact of the selection switch A, the attenuation circuit is connected with the selection switch B, the normally closed contact of the selection switch B is connected with the analog-to-digital conversion unit, and the normally open contact of the selection switch B is connected with the analog-to-digital conversion unit through the amplification circuit.

Preferably, the switch driving module includes a switch driving circuit a and a switch driving circuit B, the switch driving circuit a is configured to drive the selector switch a, the switch driving circuit B is configured to drive the selector switch B, the switch driving circuit a and the switch driving circuit B have the same structure, the switch driving circuit a includes a power supply, a relay a, a resistor R3, a triode Q3, a diode D3 and a spring a, a base of the triode Q3 is connected to the signal detection module through a resistor R3, an emitter of the triode Q3 is grounded, a collector of the triode Q3 is connected to one end of a coil of the relay a, another end of the coil of the relay a is connected to the power supply, two sides of the coil of the relay a are connected in parallel to a diode D3, a cathode of the diode D3 is connected to the power supply, an anode of the diode D3 is connected to a collector of the triode Q3, the normally open contact of the relay A is connected with one end of a spring A, the other end of the spring A is connected with a power supply, and two ends of the spring A are respectively connected with the normally open contact and the normally closed contact of the selector switch A.

The measuring amplifier is divided into three ranges, namely a high range, a middle range and a low range, the high range is used for measuring signals with large amplitude, the middle range is used for measuring signals with moderate amplitude, the low range is used for measuring signals with weak amplitude, the signal detection module is used for detecting the amplitude of the acquired audio signals and selecting different ranges for signal processing according to the amplitude, when the high range is selected, the switch driving circuit A drives a coil of the relay A to be electrified, a normally open contact of the relay A is closed, the spring A is electrified and contracted, the normally open contact of the selector switch A is closed, the normally closed contact is opened, the acquired audio signals enter the attenuation circuit through the selector switch A and then enter the analog-to-digital conversion module through the selector switch B; when the middle range is selected, the switch driving circuit A does not drive the coil of the relay A to be electrified, the switch driving circuit B does not drive the coil of the relay B to be electrified, and the acquired audio signal enters the selection switch B through the selection switch A and then enters the analog-to-digital conversion module through the selection switch B; when selecting the low range, switch drive circuit B drive relay B's coil circular telegram, relay B's normally open contact is closed, and spring B circular telegram contracts, and select switch B's normally open contact is closed, and normally closed contact breaks off, and the audio signal of gathering enters into select switch B through select switch A, and rethread select switch B enters into amplifier circuit, and the last analog-to-digital conversion module that enters into from amplifier circuit can measure the signal that range is very big, range is moderate and range is weak, has enlarged the range scope.

The invention has the beneficial effects that:

1) the signal processing unit amplifies the weak signal according to the amplitude of the acquired audio signal, attenuates the large signal, does not process the rest signals, performs analog-to-digital conversion on the audio signal processed by the signal processing unit, and sends the audio signal to the micro-processing module to calculate and acquire the actual measured value of the acquired audio signal, so that the measurement precision and the range of the measurement amplifier are enlarged, the measurement requirements of the weak signal and the large signal can be met, and the background noise of the measurement amplifier is reduced;

2) the acquired audio signals are processed by the signal processing unit and then enter the amplifying circuit A and the amplifying circuit B at the same time, the amplifying times of the amplifying circuit A and the amplifying circuit B are different and are respectively connected with two independent channels of the analog-to-digital conversion module, and the data after analog-to-digital conversion are mixed and operated by the micro-processing module so as to improve the dynamic range of the circuit. The microprocessor automatically realizes the switching of the amplifying circuit A and the amplifying circuit B according to the amplitude of the input signal, and the whole switching process is realized by software, so that the response speed is high, and zero time delay can be realized. Through the two amplifying circuits with different amplification factors, the signal can be always kept in a range close to the full range of the analog-digital conversion module, the distortion of the signal is reduced, and the conversion precision is improved.

Drawings

Fig. 1 is a schematic structural diagram of embodiment 1 of the present invention.

Fig. 2 is a schematic diagram of a relay drive circuit according to embodiment 1 of the present invention.

Fig. 3 is a schematic structural diagram of embodiment 2 of the present invention.

Fig. 4 is a schematic circuit diagram of a switch driving module according to embodiment 2 of the present invention.

In the figure, 1, a signal acquisition unit, 2, a signal processing unit, 3, a program control unit, 4, an analog-digital conversion unit, 5, a micro-processing module, 21, signal relays A and 22, signal relays B and 23, an attenuation circuit, 24, an amplification circuit, 25, a signal detection module, 26, driving circuits A and 27, driving circuits B and 31, amplification circuits A and 32, amplification circuits B and 211, selection switches A and 212, selection switches B and 213, switch driving circuits A and 214, switch driving circuits B and 215, springs A and 216 and springs B are arranged.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.

Example 1: the measuring amplifier for measuring the audio signal of the embodiment, as shown in fig. 1, includes a signal collecting unit 1, a signal processing unit 2, a program control unit 3, an analog-to-digital conversion unit 4, and a micro-processing module 5, where the signal processing unit includes a signal relay a21, a signal relay B22, an attenuation circuit 23, an amplification circuit 24, a relay driving circuit, and a signal detection module 25, the program control unit includes an amplification circuit a31 and an amplification circuit B32, and the relay driving circuit includes a driving circuit a26 and a driving circuit B27. In this embodiment, the signal detection module is a single chip with an audio signal amplitude determination program inside, and the analog-to-digital conversion unit is a dual-channel analog-to-digital converter.

The input end of the signal detection module is connected with the signal acquisition unit, the output end of the signal detection module is connected with the input end of the driving circuit A and the input end of the driving circuit B, the output end of the driving circuit A is connected with the signal relay A, the output end of the driving circuit B is connected with the signal relay B, the signal acquisition unit is connected with the signal relay A, the normally closed contact KA1 of the signal relay A is connected with the signal relay B, the normally open contact KA2 of the signal relay A is connected with the attenuation circuit, the attenuation circuit is connected with the signal relay B, the normally open contact KB2 of the signal relay B is connected with the amplification circuit A, the normally closed contact KB1 of the signal relay B is connected with the input ends of the amplification circuit A and the amplification circuit B, the amplification circuit A is connected with the amplification circuit B in parallel, the output ends of the amplification circuit A and the amplification circuit B are respectively connected with different channels of the dual-channel analog, the output end of the double-channel analog-to-digital converter is connected with the micro-processing module.

As shown in fig. 2, the relay driver circuit has a driver circuit a on the left side and a driver circuit B on the right side, and the driver circuit a and the driver circuit B have the same configuration. The driving circuit A comprises a relay power supply, a resistor R1, a triode Q1 and a diode D1, wherein the base electrode of the triode Q1 is connected with the signal detection module through a resistor R1, the emitter electrode of the triode Q1 is grounded, the collector electrode of the triode Q1 is connected with one end of a coil of the signal relay A, the other end of the coil of the signal relay A is connected with the relay power supply, the two sides of the coil of the signal relay A are connected with the diode D1 in parallel, the cathode of the diode D1 is connected with the relay power supply, and the anode of the diode D1 is connected with the collector electrode of the triode Q1.

The measuring amplifier is divided into three measuring ranges, namely a high measuring range, a middle measuring range and a low measuring range, wherein the high measuring range is used for measuring signals with large amplitude, the middle measuring range is used for measuring signals with moderate amplitude, and the low measuring range is used for measuring signals with weak amplitude. The signal acquisition unit acquires audio signals, the signal detection module acquires the audio signals from the signal acquisition unit, judges the amplitude of the acquired audio signals, and selects different ranges for signal processing according to the amplitude.

When a high range is selected, the driving circuit A receives a driving signal of the signal detection module, the coil KA of the signal relay A is controlled to be electrified, the normally closed contact KA1 of the signal relay A is disconnected, the normally open contact KA2 is closed, the driving circuit B does not receive the driving signal of the signal detection module, the coil KB of the signal relay B is not electrified, the normally closed contact KB1 of the signal relay B is closed, the normally open contact KB2 is disconnected, the collected audio signal enters the attenuation circuit through the signal relay A and then enters the amplification circuit A and the amplification circuit B through the signal relay B; when the medium range is selected, the driving circuit A and the driving circuit B do not receive a driving signal of the signal detection module, a coil KA of the signal relay A and a coil KB of the signal relay B are not electrified, a normally closed contact KA1 of the signal relay A is closed, a normally open contact KA2 is opened, a normally closed contact KB1 of the signal relay B is closed, a normally open contact KB2 is opened, the collected audio signal enters the signal relay B through the signal relay A, and then enters the amplifying circuit A and the amplifying circuit B through the signal relay B; when selecting the low range, drive circuit B receives the drive signal of signal detection module, control signal relay B's coil KB circular telegram, signal relay B's normally closed contact KB1 disconnection, normally open contact KB2 is closed, drive circuit A does not receive the drive signal of signal detection module, signal relay A's coil KA is not circular telegram, signal relay A's normally closed contact KA1 is closed, normally open contact KA2 disconnection, the audio signal of collection enters into signal relay B through signal relay A, rethread signal relay B enters into amplifier circuit, at last from amplifier circuit entering amplifier circuit A and amplifier circuit B simultaneously.

The amplification times of the amplifying circuit A and the amplifying circuit B are different, the amplifying circuits A and the amplifying circuit B are respectively connected with two independent channels of the dual-channel analog-to-digital converter, the data after analog-to-digital conversion are subjected to mixed operation by the micro-processing module, the actual measured value of the audio signal is obtained, and the dynamic range of the circuit is improved.

The signal processing unit amplifies the weak signal according to the amplitude of the acquired audio signal, attenuates the large signal, does not process the rest signals, performs analog-to-digital conversion on the audio signal processed by the signal processing unit, and sends the audio signal to the micro-processing module to calculate and acquire the actual measured value of the acquired audio signal, so that the measurement precision and the range of the measurement amplifier are expanded, and the measurement requirements of the weak signal and the large signal can be met; the microprocessor automatically realizes the switching of the amplifying circuit A and the amplifying circuit B according to the amplitude of the input signal, and the whole switching process is realized by software, so that the response speed is high, and zero time delay can be realized. Through the two amplifying circuits with different amplification factors, the signal can be always kept in a range close to the full range of the analog-digital conversion module, the distortion of the signal is reduced, and the conversion precision is improved.

Assuming that the noise value generated by the amplifier circuit at unity gain is V1, the amplification factor is N1, the noise value generated by the amplifier circuit a and the amplifier circuit B at unity gain is V2, the amplification factor is 1, and the noise value generated by the dual-channel analog-to-digital converter is V3, the total noise value of the signals received by the micro-processing module is:after the operation of the microprocessor, the actual noise energy value is as follows:the background noise value of the measuring amplifier is effectively reduced.

Example 2: a measurement amplifier for audio signal measurement of the present embodiment, as shown in fig. 3, is different from embodiment 1 in that a signal processing unit in the present embodiment includes a selection switch a211, a selection switch B212, an attenuation circuit, an amplification circuit, a switch driving module, and a signal detection module, and the switch driving module includes a switch driving circuit a213 and a switch driving circuit B214.

The input end of the signal detection module is connected with the signal acquisition unit, the output end of the signal detection module is connected with the input end of the switch driving circuit A and the input end of the switch driving circuit B, the output end of the switch driving circuit A is connected with the selection switch A, the output end of the switch driving circuit B is connected with the selection switch B, the signal acquisition unit is connected with the selection switch A, the normally closed contact KA11 of the selection switch A is connected with the selection switch B, the normally open contact KA22 of the selection switch A is connected with the attenuation circuit, the attenuation circuit is connected with the selection switch B, the normally open contact KB22 of the selection switch B is connected with the amplification circuit, the normally closed contact KB11 of the selection switch B is connected with the input ends of the amplification circuit A and the amplification circuit B, the amplification circuit A is connected with the input ends of the amplification circuit A and the amplification circuit B in parallel, the output ends of the amplification circuit A and the amplification circuit B are respectively connected with different channels of the, the output end of the double-channel analog-to-digital converter is connected with the micro-processing module.

As shown in fig. 4, the switch driving module has a switch driving circuit a on the left side and a switch driving circuit B on the right side, and the switch driving circuit a and the switch driving circuit B have the same structure. The switch driving circuit A comprises a power supply, a relay A, a resistor R3, a triode Q3, a diode D3 and a spring A, wherein the base electrode of the triode Q3 is connected with a signal detection module through a resistor R3, the emitter electrode of the triode Q3 is grounded, the collector electrode of the triode Q3 is connected with one end of a coil of the relay A, the other end of the coil of the relay A is connected with the power supply, the diode D3 is connected to the two sides of the coil of the relay A in parallel, the cathode of the diode D3 is connected with a secondary power supply, the anode of the diode D3 is connected with the collector electrode of the triode Q3, a normally-open contact KJA of the relay A is connected with one end of the spring A, and the other end of the spring A is connected with the power supply. Two ends of the spring A215 are respectively connected with a normally open contact KA22 and a normally closed contact KA11 of the selector switch A, and two ends of the spring B216 are respectively connected with a normally open contact KB22 and a normally closed contact KB11 of the selector switch B.

The measuring amplifier is divided into three measuring ranges, namely a high measuring range, a middle measuring range and a low measuring range, wherein the high measuring range is used for measuring signals with large amplitude, the middle measuring range is used for measuring signals with moderate amplitude, and the low measuring range is used for measuring signals with weak amplitude. The signal acquisition unit acquires audio signals, the signal detection module acquires the audio signals from the signal acquisition unit, judges the amplitude of the acquired audio signals, and selects different ranges for signal processing according to the amplitude.

When a high range is selected, the switch driving circuit A receives a driving signal of the signal detection module, the coil of the relay A is controlled to be electrified, the normally open contact KJA of the relay A is closed, the spring A is electrified and contracted, the normally open contact KA22 of the selection switch A is closed, the normally closed contact KA11 is disconnected, and the collected audio signal enters the attenuation circuit through the selection switch A and then enters the amplification circuit A and the amplification circuit B through the selection switch B; when the middle measuring range is selected, the switch driving circuit A and the switch driving circuit B do not receive a driving signal of the signal detection module, a coil of the relay A and a coil of the relay B are not electrified, the spring A and the spring B are not contracted, a normally closed contact KA11 of the selector switch A is closed, a normally open contact KA22 is disconnected, a normally closed contact KB11 of the selector switch B is closed, a normally open contact KB22 is disconnected, and the acquired audio signal enters the selector switch B through the selector switch A and then simultaneously enters the amplifying circuit A and the amplifying circuit B through the selector switch B; when selecting the low-range, switch drive circuit B receives the drive signal of signal detection module, and control relay B's coil circular telegram, relay B's normally open contact KJB is closed, and the spring B circular telegram is received, and select switch B's normally open contact KB22 is closed, and normally closed contact KA11 disconnection, and the audio signal of gathering enters into select switch B through select switch A, and the rethread select switch B enters into amplifier circuit, and the follow amplifier circuit simultaneously gets into amplifier circuit A and amplifier circuit B at last.

The amplification times of the amplifying circuit A and the amplifying circuit B are different, the amplifying circuits A and the amplifying circuit B are respectively connected with two independent channels of the dual-channel analog-to-digital converter, the data after analog-to-digital conversion are subjected to mixed operation by the micro-processing module, the actual measured value of the audio signal is obtained, and the dynamic range of the circuit is improved.