Automatic calibration device for condenser microphone

Abstract

The utility model discloses an automatic calibration device for a condenser microphone. The automatic calibration device comprises a PC (Personal Computer), a main control module and an electrostatic excitation module which are connected in sequence, the main control module comprises a main control unit, an RS485 communication unit, a user display unit and a data storage unit, and the RS485 communication unit, the user display unit and the data storage unit are all connected with the main control unit; the electrostatic excitation module comprises a signal generation circuit, a pole plate and a signal acquisition unit, wherein the signal generation circuit comprises an oscillation circuit, an amplification circuit and a filter circuit which are connected in sequence. According to the utility model, the automatic calibration device is additionally arranged on the basis of the original equipment aiming at the condenser microphone which is installed on site but does not have a calibration function, so that errors caused by manual operation in the traditional calibration process are simplified, and the measurement precision and the calibration efficiency of the original equipment are improved.

Description

Technical Field

[0001] This utility model relates to the field of microphone technology, and in particular to an automatic calibration device for condenser microphones. Background Technology

[0002] Sound signal acquisition plays a vital role in numerous fields, including environmental noise monitoring, architectural acoustics optimization, and audio equipment performance evaluation. As people place increasing emphasis on sound quality and noise management, the demand for high-precision and high-efficiency sound measurement equipment is also rising. High-sensitivity condenser microphones and high-accuracy data acquisition systems have become key approaches to improving the reliability of sound signals.

[0003] However, due to factors such as prolonged operation or environmental changes, condenser microphones may experience sensitivity fluctuations, requiring inspection and calibration to avoid deviations in results.

[0004] Currently, condenser microphones generally rely on manual calibration, which has poor environmental adaptability, and improper operation may lead to measurement results deviating from reality. Furthermore, condenser microphones have a weak ability to maintain stable measurements in dynamic acoustic environments, affecting the reliability of the measurement results. Therefore, developing an automatic calibration device for condenser microphones, especially for sound measurement devices already installed in the field but lacking calibration functionality, is of great significance. This device should be able to automatically adapt to environmental changes, automatically collect and analyze data, reduce human intervention in experiments, and improve the efficiency of calibration measurements. In addition, the rational design of the signal generation circuit is crucial to the accuracy of the self-calibration device and is a core module of the calibration system. A well-designed, low-power, high-precision signal generation circuit is beneficial for providing stable excitation signals that meet specific requirements for calibration testing, thus improving the accuracy and consistency of measurements. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] Based on this, the present invention provides an automatic calibration device for condenser microphones to solve the error caused by human operation in the traditional calibration process, improve the calibration efficiency, and the reasonable design of the signal generation circuit provides an important reference for the optimization of the self-calibration device.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, this utility model provides an automatic calibration device for a condenser microphone, comprising a PC, a main control module, and an electrostatic excitation module connected in sequence. The main control module includes a main control unit, an RS485 communication unit, a user display unit, and a data storage unit, all of which are connected to the main control unit. The electrostatic excitation module includes a signal generation circuit, an electrode plate, and a signal acquisition unit. The signal generation circuit includes an oscillation circuit, an amplification circuit, and a filtering circuit connected in sequence. The output of the signal generation circuit is connected to the electrode plate, the electrode plate is connected to the condenser microphone, the condenser microphone is connected to the input of the signal acquisition unit, and the output of the signal acquisition unit is connected to the main control unit.

[0009] Optionally, the filtering circuit includes a first amplifier, a second amplifier, a third amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a first capacitor and a second capacitor. In the filtering circuit, the inverting input terminal of the first amplifier is connected to the amplification circuit through the first resistor and to the output terminal of the first amplifier through the second resistor. The non-inverting input terminal of the first amplifier is connected to the plate through the fifth resistor and to ground through the sixth resistor. The output terminal of the first amplifier is connected to the inverting input terminal of the second amplifier through the fourth resistor. The inverting input terminal of the second amplifier is connected to the plate through the first capacitor and to the output terminal of the second amplifier through the first capacitor. The non-inverting input terminal of the second amplifier is grounded. The output terminal of the second amplifier is connected to the inverting input terminal of the third amplifier through the seventh resistor. The inverting input terminal of the third amplifier is connected to the output terminal of the third amplifier through the second capacitor. The non-inverting input terminal of the third amplifier is grounded. The output terminal of the third amplifier is connected to the inverting input terminal of the first amplifier through the third resistor.

[0010] Optionally, the fourth resistor and the seventh resistor have the same parameters, and the first capacitor and the second capacitor have the same parameters.

[0011] Optionally, the oscillation circuit does not require an external input signal to oscillate; it generates a 900Hz sine wave itself through feedback.

[0012] Optionally, the amplification factor of the amplifier circuit is 20.

[0013] Optionally, three power supply circuits and two protection circuits are used to provide ±12V and ±5V stable voltages for the electrostatic excitation module.

[0014] Optionally, the main control module circuit uses an STM32F302RBT high-performance ARM Cortex-M4 microcontroller.

[0015] Optionally, the signal acquisition unit uses a CS5361-KSZR high-precision low-noise AD converter with a resolution of 24 bits, and the AD converter operates in I2S protocol slave mode.

[0016] (III) Beneficial Effects

[0017] The above-mentioned technical solution of this utility model has the following advantages:

[0018] 1. The automatic calibration device for condenser microphones enables calibration and testing of condenser microphones. The device integrates a main control module and an electrostatic excitation module, and has built-in signal generation circuits and real-time data acquisition units. It can perform automated measurement and analysis, simplifying the errors caused by manual operation in the traditional calibration process and improving calibration efficiency and accuracy.

[0019] 2. The signal generation circuit provided by this utility model, which is configured by combining an oscillation circuit, an amplification circuit, and a filtering circuit, provides a stable excitation signal with a frequency and amplitude that meet the preset requirements for the electrostatic excitation module, thereby ensuring the stability and reliability of the automatic calibration device test.

[0020] 3. The filter circuit provided by this utility model has a flexible frequency response design. It can be configured as a high-pass, low-pass, or band-pass filter by adjusting the values ​​of resistors and capacitors to meet different application requirements. Moreover, through an appropriate feedback mechanism, the circuit can maintain good phase linearity, reduce signal distortion, and achieve a higher Q value filtering effect. Attached Figure Description

[0021] The features and advantages of this invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0022] Figure 1 This is a schematic diagram of the frame structure of an embodiment of the present utility model;

[0023] Figure 2 This is a circuit diagram of the signal generation circuit according to an embodiment of the present invention;

[0024] Figure 3 This is a diagram showing the three power supply circuits of the electrostatic excitation module in an embodiment of this utility model. Figure 3 (a) is a circuit diagram for converting 12V to 5V. Figure 3 (b) is a circuit diagram for converting 12V to -12V. Figure 3 (c) is a circuit diagram for converting 5V voltage to -5V voltage;

[0025] Figure 4 This is a diagram showing two protection circuits for the electrostatic excitation module in an embodiment of this utility model. Figure 4 (a) Circuit diagram for reverse connection and overcurrent protection. Figure 4 (b) Circuit diagram for reverse connection and overvoltage protection;

[0026] Figure 5 This is a circuit diagram of the main control module according to an embodiment of the present invention. Figure 5 (a) is the circuit diagram of the main control unit. Figure 5 (b) is the circuit diagram of the RS485 data transmission unit. Figure 5 (c) is the circuit diagram of the data storage unit. Figure 5 (d) Display the unit circuit diagram to the user;

[0027] Figure 6 This is a circuit diagram of the signal acquisition unit according to an embodiment of the present invention. Figure 6 (a) is a circuit diagram of a signal amplifier. Figure 6 (b) is the circuit diagram for signal acquisition. Detailed Implementation

[0028] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit the scope of this utility model.

[0029] like Figure 1 As shown, the automatic calibration device for a condenser microphone of this invention includes a PC, a main control module, and an electrostatic excitation module connected in sequence. The main control module includes a main control unit, an RS485 communication unit, a user display unit, and a data storage unit, all of which are connected to the main control unit. The electrostatic excitation module includes a signal generation circuit, an electrode plate, and a signal acquisition unit. The signal generation circuit includes an oscillation circuit, an amplification circuit, and a filtering circuit connected in sequence. The output of the signal generation circuit is connected to the electrode plate, the electrode plate is connected to the condenser microphone, the condenser microphone is connected to the input of the signal acquisition unit, and the output of the signal acquisition unit is connected to the main control unit.

[0030] The working principle of the automatic calibration device for condenser microphones is as follows: The user sends control commands to the main control module via fiber optic communication using a PC. After receiving the commands, the main control module controls the electrostatic excitation module to generate and amplify the excitation signal, which is applied to the electrodes. The electrodes excite the condenser microphone under test to respond. Then, the signal acquisition unit in the excitation module collects the condenser microphone response data in real time and feeds it back to the main control module. The main control module compares the excitation signal with the condenser microphone response. If the deviation of the condenser microphone response exceeds the set value, it prompts the user to adjust the parameters of the condenser microphone to meet the standard requirements. Simultaneously, the main control module transmits data via the RS485 communication unit. The user display unit displays relevant data and information after calibration and testing, and the data storage unit saves the data and time information of this calibration and testing.

[0031] In one specific embodiment, the signal generating circuit includes an oscillation circuit, an amplification circuit, and a filtering circuit connected in sequence, such as... Figure 2 As shown, the oscillation circuit can also be other electronic circuits with the same function. The oscillation circuit does not require an external input signal to oscillate; it generates a sine wave through feedback. The frequency is determined by the RC parameters (C12, C13, R12, R15) of U4.1. In this embodiment, the control parameters make the oscillation circuit output a sine wave with a frequency of 900Hz. The amplifier circuit can also be other electronic circuits with the same function, which further amplifies the sine wave signal generated by the oscillation circuit by 20 times and increases the output current and power. Finally, the amplified signal generated by the amplifier circuit passes through a filter circuit to form an excitation signal with a specific amplitude and frequency, which is output to the electrode plate and realizes the calibration and detection of the condenser microphone.

[0032] like Figure 2 As shown, the filter circuit includes amplifiers U7.1, U8.1, and U8.2, resistors R25, R26, R27, R28, R29, R30, and R31, and capacitors C18 and C19. In this filter circuit, the inverting input of amplifier U7.1 is connected to the amplifier circuit via resistor R25 and to its output via resistor R26. The non-inverting input of amplifier U7.1 is connected to the plate via resistor R29 and grounded via resistor R30. The output of amplifier U7.1 is connected to the inverting input of amplifier U8.1 via resistor R28. The inverting input of amplifier U8.1 is connected to the plate via capacitor C18 and to its output via capacitor C18. The non-inverting input of amplifier U8.1 is grounded. The output of amplifier U8.1 is connected to the inverting input of amplifier U8.2 via resistor R31. The inverting input terminal of amplifier U8.2 is connected to the output terminal of amplifier U8.2 through capacitor C19, the non-inverting input terminal of amplifier U8.2 is grounded, and the output terminal of amplifier U8.2 is connected to the inverting input terminal of amplifier U7.1 through resistor R27.

[0033] Filtering circuits primarily control the frequency response of signals based on a combination of amplifiers and resistors / capacitors, such as... Figure 2As shown, from left to right, a summing amplifier and two integrators are cascaded to form a second-order filter. The main function of the summing amplifier is to perform a weighted summation of multiple input signals (including the feedback signal from the integrator and the input signal). This filter circuit is mainly used as a bandpass filter, but it can also be used for low-pass and high-pass outputs, making it a state-variable active filter. In this embodiment, when used as a bandpass filter output, the resistor (R28, R31) and capacitor (C18, C19) parameters of the two integrators are set to be the same, and the desired center frequency fc is obtained from the cutoff frequencies of the two integrators. When the input frequency is below fc, the signal passing through the integrator generates a feedback signal with a 180° phase lag, which is superimposed on the input signal. This creates a certain cancellation effect in the low-frequency range, reducing the output signal. Near the center frequency, the low-pass response decreases, and the feedback signal also decreases. At this point, the phase and amplitude of the feedback and input signals enhance the output signal at the desired frequency. The system response reaches its maximum when the frequency is exactly equal to fc. When the frequency is above fc, the integrator's effect weakens and gradually blocks the signal from passing through; therefore, the amplitude only reaches its maximum at the center frequency fc. Controlling the parameters of the feedback resistors (R29, R30) can achieve a filter quality factor Q of approximately 90. Compared to ordinary filter circuits, this circuit offers flexible frequency response design. By simply adjusting the values ​​of the resistors and capacitors, it can be flexibly configured as a high-pass, low-pass, or band-pass filter to meet different application requirements. Furthermore, through an appropriate feedback mechanism, this circuit design maintains good phase linearity and reduces signal distortion. In addition, compared to ordinary filter circuits, this circuit can be designed to achieve a higher Q value.

[0034] The electrostatic excitation module requires three specific power supply circuits and two protection circuits to provide stable voltages, with the required stable output voltages being ±12V and ±5V, respectively.

[0035] 3 power supply circuits as follows Figure 3 As shown, where, Figure 3 (a) Convert 12V voltage to 5V voltage using a DC-DC buck converter. Figure 3 (b) The DC power supply voltage is flipped by a power inverter chip, that is, the 12V voltage is converted to -12V voltage in this circuit. Figure 3 (c) The 5V voltage is converted to -5V by a DC voltage inverter to meet the power supply voltage requirements of the electrostatic excitation module.

[0036] Two protection circuits, such as Figure 4 As shown, the protection circuit has reverse connection protection, overcurrent protection, and overvoltage protection functions. Among them, Figure 4(a) The protection circuit uses a P-channel MOSFET Q1 and a resistor R1 to form a reverse connection protection circuit. It can only conduct when the power supply is normal, allowing the current to flow through, thereby realizing the reverse connection protection function. A 1A fuse F1 is used as an overcurrent protection device. When the current exceeds the safe value, the circuit is cut off, thereby realizing the overcurrent protection function. Zener diode D1 provides a certain protection for the MOSFET in the case of overvoltage. Figure 4 (b) The protection circuit uses capacitor C1 and Zener diode D2 in parallel, and capacitor C2 and Zener diode D3 in parallel to achieve voltage regulation, ensuring that the output voltage is kept within a stable range and avoiding voltage spikes or overvoltage effects on subsequent circuits, thereby achieving overvoltage protection; PMOS transistor Q2 plays a role in preventing reverse connection protection; in addition, the circuit can be switched on and off by the level signal issued by the microcontroller.

[0037] Main control module circuit such as Figure 5 As shown, where, Figure 5 (a) The main control unit circuit uses the STM32F302RBT high-performance ARM Cortex-M4 microcontroller with a main frequency of up to 72MHz, achieving both high-efficiency computing power and low power consumption. The main control unit circuit is connected to the RS485 data transmission unit circuit (e.g., Figure 5 (b) shown), data storage unit circuit (as shown in the data storage unit circuit) Figure 5 (c) shown) and user display unit circuit (as shown in the figure) and user display unit circuit (e.g. Figure 5 (d) As shown, the user display unit circuit uses a small monochrome OLED display chip OLED-SMD with a resolution of 128x32 pixels, supports I2C or SPI interface, and has high contrast and low power consumption.

[0038] Signal acquisition unit circuit such as Figure 6 As shown, where, Figure 6 (a) is a signal amplification circuit that applies the excitation signal to the plates to amplify the output response of the capacitor microphone to a certain extent, so as to facilitate signal acquisition. Figure 6 (b) is a signal acquisition circuit, which uses a high-precision, low-noise AD converter CS5361-KSZR with a resolution of 24 bits. The control pin makes it work in I2S protocol slave mode, and it collects response signal data in real time and feeds it back to the main control unit.

[0039] This invention addresses condenser microphones that are already installed on-site but lack calibration functionality. It adds an automatic calibration device to the existing equipment, simplifying the errors caused by manual operation in the traditional calibration process, thereby improving the measurement accuracy and calibration efficiency of the original equipment.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model, and not to limit it; although the implementation of this utility model has been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this utility model, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An automatic calibration device for a condenser microphone, characterized in that, The system includes a PC, a main control module, and an electrostatic excitation module connected in sequence. The main control module includes a main control unit, an RS485 communication unit, a user display unit, and a data storage unit, all of which are connected to the main control unit. The electrostatic excitation module includes a signal generation circuit, an electrode plate, and a signal acquisition unit. The signal generation circuit includes an oscillation circuit, an amplification circuit, and a filtering circuit connected in sequence. The output of the signal generation circuit is connected to the electrode plate, the electrode plate is connected to a condenser microphone, the condenser microphone is connected to the input of the signal acquisition unit, and the output of the signal acquisition unit is connected to the main control unit.

2. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The filtering circuit includes a first amplifier, a second amplifier, a third amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, and a second capacitor. In the filtering circuit, the inverting input terminal of the first amplifier is connected to the amplification circuit through the first resistor and to the output terminal of the first amplifier through the second resistor. The non-inverting input terminal of the first amplifier is connected to the plate through the fifth resistor and to ground through the sixth resistor. The output terminal of the first amplifier is connected to the inverting input terminal of the second amplifier through the fourth resistor. The inverting input terminal of the second amplifier is connected to the plate through the first capacitor and to the output terminal of the second amplifier through the first capacitor. The non-inverting input terminal of the second amplifier is grounded. The output terminal of the second amplifier is connected to the inverting input terminal of the third amplifier through the seventh resistor. The inverting input terminal of the third amplifier is connected to the output terminal of the third amplifier through the second capacitor. The non-inverting input terminal of the third amplifier is grounded. The output terminal of the third amplifier is connected to the inverting input terminal of the first amplifier through the third resistor.

3. The automatic calibration device for a condenser microphone according to claim 2, characterized in that, The fourth resistor and the seventh resistor have the same parameters, and the first capacitor and the second capacitor have the same parameters.

4. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The oscillation circuit does not require an external input signal to oscillate; it generates a 900Hz sine wave itself through feedback.

5. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The amplification factor of the amplifier circuit is 20.

6. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The electrostatic excitation module is provided with stable voltages of ±12V and ±5V using three power supply circuits and two protection circuits.

7. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The main control module circuit uses the STM32F302RBT high-performance ARM Cortex-M4 microcontroller.

8. The automatic calibration device for a condenser microphone according to claim 1, characterized in that, The signal acquisition unit uses a CS5361-KSZR high-precision low-noise AD converter with a resolution of 24 bits. The AD converter operates in I2S protocol slave mode.

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