Method for testing and calibrating sensitivity directivity of Fabry-Perot sensor in transformer oil

Abstract

The invention relates to a method for testing and calibrating sensitivity directivity of a Fabry-Perot sensor in transformer oil. According to the method, sensitivity response values under different conditions are obtained by adjusting the distance and the angle between the Fabry-Perot sensor and a sound source. The testing step comprises the steps of setting an initial frequency and a spacing, adjusting an angle and a distance, recording response values under various conditions, and drawing a sensor sensitivity graph through normalization calculation. According to the calibration method, the standard microphone is adopted for comparison test, and the attenuation coefficient is combined for calibration, so that the sound pressure sensitivity accuracy of the Fabry-Perot sensor is ensured. The invention provides an efficient and reliable test and calibration scheme, the application effect of the Fabry-Perot sensor in the transformer oil can be remarkably improved, the accuracy is high, and the method is suitable for a complex environment.

Description

Technical Field

[0001] The invention relates to the technical field of sensor testing and calibration, and in particular to a sensitivity directivity testing and calibration method for a Fabry-Perot sensor in transformer oil. Background Art

[0002] As the scale of modern power systems continues to expand and become more complex, the operating reliability of transformers, as core equipment in power transmission and distribution systems, directly affects the safety and stability of the entire power grid. Partial discharge in transformers is one of the main factors leading to insulation failure and is also an early warning signal of potential transformer failure. Therefore, the detection and evaluation of partial discharge is of great significance to ensure the safe operation of transformers. Ultrasonic Fabry-Perot sensors are gradually being used in the monitoring and diagnosis of partial discharge due to their high sensitivity, good frequency response characteristics, and strong anti-electromagnetic interference capabilities. However, as the sensor detection environment, the acoustic properties of transformer oil are significantly different from those of the air environment, which poses new challenges to the sound pressure sensitivity and directivity characteristics of Fabry-Perot sensors.

[0003] In order to ensure the detection accuracy of Fabry-Perot sensors in transformer oil, special sensitivity directivity tests and calibrations are required. This not only helps to accurately evaluate the sensor's ability to receive acoustic signals in transformer oil, but also provides accurate acoustic field models and data support for fault diagnosis and partial discharge detection. However, due to the significant differences between the physical properties of transformer oil, such as density, viscosity, and acoustic impedance, and those of the air environment, directly using the calibration results in the air may lead to large errors. Therefore, developing a sensitivity directivity test and calibration method for Fabry-Perot sensors specifically suitable for transformer oil environments can effectively solve this problem in sensor performance evaluation and provide reliable technical support for sensor applications under actual working conditions. The development of this method can not only improve the application effect of sensors in complex environments in oil, but also promote the further development of ultrasonic detection technology based on Fabry-Perot sensors in fault diagnosis of power equipment. Summary of the invention

[0004] The present invention provides a method for testing and calibrating the sensitivity directivity of a Fabry-Perot sensor in transformer oil. The device applicable to the method comprises: a host computer; a motor control module; an optical demodulator; a Fabry-Perot sensor; a transformer oil tank model; a sound source; a slide table, which supports the precise movement and positioning of the Fabry-Perot sensor and the sound source; a signal generator, which is used to generate a stable sound source signal. The slide table comprises a Fabry-Perot sensor transverse travel motor; a guide rail, whose internal thread cooperates with the external thread of the slider, which is used to ensure the smooth movement of the slider in the slide rail groove; a Fabry-Perot sensor rotation motor, which moves the slider through the slide The block is connected with the turntable; the slider; the turntable is connected with the Fabry sensor through the Fabry sensor connecting rod; the sound source rotating motor; the sound source lateral travel motor; the sound source fixing inverted Ω clamp connected with the sound source connecting rod for stabilizing the sound source; the connecting rod, including the Fabry sensor connecting rod and the sound source connecting rod, respectively used to connect the Fabry sensor and the sound source with the corresponding turntable; the slide rail groove; the limit block; the Fabry sensor fixing L-shaped inverted Ω clamp connected with the Fabry sensor connecting rod for clamping the Fabry sensor; the slide table holder is used to firmly clamp the slide table on the transformer mailbox model;

[0005] S1: The device is powered on, the initial frequency of the sound source is set to f0, and the initial distance between the sound source and the Fabry-Perot sensor is set to X0, where X0 is greater than the minimum distance and less than the maximum distance;

[0006] S2: Control the Fabry-Perot sensor rotation motor and the sound source rotation motor so that the angle between the Fabry-Perot sensor sensitive diaphragm plane and the sound source plane is 0°;

[0007] S3: Control the motor of the Fabry-Perot sensor to change the turntable angle by 10° or 30° steps. The turntable angle is in the range of [0, 360°), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, and recording the response values ​​Yd00, Yd01, Yd02, ... at different angles when the spacing is X0;

[0008] S4: Control the lateral travel motor of the Fabry-Perot sensor and the lateral travel motor of the sound source, change the distance X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source, repeat step S3, and record the response values ​​at different angles:

[0009] Yd10, Yd11, Yd12,…;

[0010] Yd20, Yd21, Yd22,…;

[0011] Yd30, Yd31, Yd32,…;

[0012] …;

[0013] Ydn0, Ydn1, Ydn2,…;

[0014] S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test:

[0015] Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……;

[0016] Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…;

[0017] Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…;

[0018] ……;

[0019] Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,…;

[0020] Based on the calculation results, draw the sensor directional sensitivity diagram;

[0021] S6: Change the sound source frequency, repeat steps S2-S5, and draw a directional sensitivity diagram of the sensor at different frequencies.

[0022] Beneficial effects:

[0023] The present invention provides an efficient and reliable testing and calibration solution, which can significantly improve the application effect of Fabry-Perot sensors in transformer oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A diagram of a device used for directivity testing according to an embodiment of the present invention;

[0025] Figure 2 A structural diagram of a slide according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of the minimum distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0027] Figure 4 A schematic diagram of an arbitrary distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0028] Figure 5 A schematic diagram of the maximum distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention;

[0029] Figure 6 A schematic diagram of the angle change between the Fabry-Perot sensor and the sound source plane according to an embodiment of the present invention;

[0030] Figure 7 A flow chart of a test process in a method for testing and calibrating the sensitivity directivity of a Fabry-Perot sensor in transformer oil according to an embodiment of the present invention;

[0031] Figure 8 It is a flow chart of the calibration process in the sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil;

[0032] Fig. 9 This is a sensitivity directivity test diagram of a Fabry-Perot sensor in transformer oil according to an embodiment of the present invention.

[0033] Figure markings: 1-host computer; 2-motor control module; 3-optical demodulator; 4-Fabry-Perot sensor; 5-transformer oil tank model; 6-silence cotton; 7-sound source; 8-slide; 9-signal generator; 801-Fabry-Perot sensor lateral travel motor; 802-guide rail; 803-Fabry-Perot sensor rotation motor; 804-slide; 805-turntable; 806-sound source rotation motor; 807-sound source lateral travel motor; 808-sound source fixed inverted Ω clamp; 809-connecting rod; 810-slide rail groove; 811-limiting block; 812-Fabry-Perot sensor fixed L-shaped inverted Ω clamp; 813-slide holder. DETAILED DESCRIPTION

[0034] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms, and the present disclosure should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0035] Figure 1 FIG. 2 is a diagram of a device used for directivity testing according to an embodiment of the present invention. Figure 1 As shown in the figure, the device used for the test mainly includes the following components: a host computer 1, which is used to control the test process and process data; a motor control module 2, which is responsible for controlling the movement and rotation of the Fabry-Perot sensor and the sound source; an optical demodulator 3, which is used to receive and demodulate the sound signal detected by the Fabry-Perot sensor; a Fabry-Perot sensor 4, which performs testing by sensing the change of the sound signal; a transformer tank model 5, which simulates the working environment of the transformer; a sound-absorbing cotton 6, which is used to reduce the reflection of sound waves; a sound source 7, which provides a sound signal with adjustable frequency; a slide 8, which supports the precise movement and positioning of the Fabry-Perot sensor and the sound source; and a signal generator 9, which is used to generate a stable sound source signal.

[0036] Figure 2 FIG. 1 is a structural diagram of a slide according to an embodiment of the present invention. Figure 2As shown, the slide mainly includes a Fabry-Perot sensor transverse travel motor 801, which is used to control the precise movement of the Fabry-Perot sensor in the horizontal direction to ensure that the displacement of the sensor during the test is controllable. The external thread of the guide rail 802 cooperates with the internal thread of the slider 804 to ensure the smooth movement of the slider 804 in the slide rail groove 810. The Fabry-Perot sensor rotation motor 803 is connected to the slider 804 and the turntable 805 through the slider 804, and is responsible for adjusting the rotation angle of the sensor so that it can perform multi-angle testing, thereby achieving the directivity measurement of sensitivity. The slider 804 is located on the slide and is used to support and guide the movement of the Fabry-Perot sensor to ensure that the slide system has good stability and vibration resistance during operation. Its diameter is smaller than the slide rail groove 810, and its stroke is between the Fabry-Perot sensor transverse travel motor 801 and the limit block 811. The turntable 805 is connected to the Fabry-Perot sensor rotation motor 803, supports the angle adjustment of the Fabry-Perot sensor during rotation, and ensures that it can work stably at different angles. The sound source rotating motor 806 is connected to the turntable through the corresponding slider, which is used to control the rotation of the sound source, thereby adjusting the incident direction of the sound wave, and cooperating with the Fabry-Perot sensor to perform sensitivity tests in different directions. The sound source lateral travel motor 807 adjusts the distance between the sound source and the sensor by moving the sound source horizontally, so that the test can cover different distance ranges. The sound source fixed inverted Ω clamp 808 is connected to the sound source connecting rod to stabilize the sound source, ensure that it remains stable during movement or rotation, and prevent test errors caused by offset. The connecting rod 809 includes a Fabry-Perot sensor connecting rod and a sound source connecting rod, which are respectively used to connect the Fabry-Perot sensor and the sound source to their respective corresponding turntables to ensure the stability of the overall structure. The Fabry-Perot sensor fixed L-shaped inverted Ω clamp 812 is connected to the Fabry-Perot sensor connecting rod to clamp the Fabry-Perot sensor 4 so that the plane of its sensitive diaphragm coincides with the axis of the Fabry-Perot sensor connecting rod to ensure that when the sensor rotates, the distance between the response sensitive area and the sound source remains unchanged. The slide holder 813 is used to firmly clamp the slide on the transformer mailbox model 5 to ensure the stability of the equipment during the test.

[0037] When the sliders on both sides (slider 804 and the slider corresponding to the sound source rotating motor 806) are close to the limit block, there is a minimum distance Xmin between the Fabry-Perot sensor 4 and the sound source 7. When the sliders on both sides are close to the motors at both ends, there is a maximum detection Xmax between the Fabry-Perot sensor 4 and the sound source 7. This structure limits the stroke of the slider 804, and the specific value is determined according to actual detection needs.

[0038] Figure 3 FIG. 1 is a schematic diagram of the minimum distance between the Fabry-Perot sensor and the sound source according to an embodiment of the present invention. Figure 3As shown, the minimum distance Xmin set between the Fabry-Perot sensor 4 and the sound source 7 is intended to ensure that the sensor can effectively receive the sound signal without interference during the sensitivity test. The setting of the minimum distance helps to avoid signal distortion caused by too close distance, and ensures that the sensor collects data in the best receiving state. By adjusting the slide system, the distance between the Fabry-Perot sensor and the sound source can be accurately controlled, so as to ensure that it is always kept above this minimum value during the test.

[0039] Figure 4 FIG. 1 is a schematic diagram of an arbitrary distance between a Fabry-Perot sensor and a sound source according to an embodiment of the present invention. Figure 4 As shown in the figure, the distance between the Fabry-Perot sensor and the sound source can be set at any distance. This flexibility allows the test to adapt to a variety of experimental conditions. In practical applications, according to different test requirements, the distance between the Fabry-Perot sensor and the sound source can be freely adjusted to achieve a comprehensive evaluation of the sensor performance. This arbitrary spacing setting provides greater convenience for subsequent testing and calibration.

[0040] Figure 5 FIG. 1 is a schematic diagram of the maximum distance between the Fabry-Perot sensor and the sound source according to an embodiment of the present invention. Figure 5 As shown, the maximum distance Xmax set between the Fabry-Perot sensor 4 and the sound source 7 is marked, which is intended to ensure the effectiveness of the sound signal during propagation and the sensor's receiving ability. In the sensitivity test, the maximum distance is set to prevent the sound signal from attenuating to the point where it cannot be effectively captured by the sensor. Through the precise control of the slide, the Fabry-Perot sensor and the sound source can be kept within the maximum detection range to ensure the accuracy and reliability of the test data.

[0041] Figure 6 FIG. 1 is a schematic diagram of the angle change between the Fabry-Perot sensor and the sound source plane according to an embodiment of the present invention. Figure 6 As shown, the initial angle between the Fabry-Perot sensor 4 and the sound source 7 is 0°. During the test, the Fabry-Perot sensor rotates in a clockwise direction to detect the sensitivity at different angles. When the sound source position remains unchanged, the plane of the Fabry-Perot sensor rotates clockwise, and the detection accuracy can be specified according to actual needs, and the step can be 10° or 30°. In this schematic diagram, the angles between the axis of the sensitive diaphragm of the Fabry-Perot sensor and the horizontal axis are 30° and 270° respectively, giving a schematic diagram of the position of the sensor at different angles.

[0042] Figure 7 The flowchart of the test process of the sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil according to the embodiment of the present invention is shown in FIG. Figure 7 As shown, the main steps are:

[0043] S1: Power on the device, set the initial frequency of the sound source to f0, and the initial distance between the sound source and the Fabry-Perot sensor to X0 (Xmin≤X0≤Xmax);

[0044] S2: Control the Fabry-Perot sensor rotation motor 803 and the sound source rotation motor 806 so that the angle between the plane of the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source is 0°;

[0045] S3: Control the Fabry-Perot sensor to rotate the motor 803, and change the turntable angle by 10° or 30° (range [0, 360°)), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, and recording the response values ​​Yd00, Yd01, Yd02, ... measured by the optical demodulator at different angles when the spacing X0 is recorded;

[0046] S4: Control the lateral travel motor 801 of the Fabry-Perot sensor and the lateral travel motor 807 of the sound source, change the distance X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source, repeat step S3, and record the response values ​​at different angles:

[0047] Yd10, Yd11, Yd12, ...;

[0048] Yd20, Yd21, Yd22, ...;

[0049] Yd30, Yd31, Yd32, ...;

[0050] …;

[0051] Ydn0, Ydn1, Ydn2, ...;

[0052] X1, X2, ..., Xn are set in the following way: between the minimum and maximum distances, including but not limited to 50mm or 100mm step settings, such as X1 = Xmin + 50mm, X2 = X1 + 50mm, ..., Xn = Xmin + n 50mm.

[0053] S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test:

[0054] Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……;

[0055] Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…;

[0056] Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…;

[0057] ……;

[0058] Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,….

[0059] Based on the calculation results, the sensor directional sensitivity diagram is drawn. The drawing method includes taking the maximum value of the optical demodulator response obtained from the actual test as the normalized denominator (generally the response value Yd00 when the angle between the sensitive diaphragm plane of the nearest Fabry-Perot sensor and the sound source plane is 0°), and other values ​​at different distances and angles as the normalized numerators, and obtaining different normalized values, which are drawn in the radar chart as the directional sensitivity diagram.

[0060] S6: Change the sound source frequency, such as 20kHz, 40kHz, 60kHz. The specific step is determined according to the actual measurement requirements, including but not limited to 20kHz step. Repeat steps S2-S5 to draw the sensor directional sensitivity diagram at different frequencies.

[0061] Figure 8 The calibration process flow chart of the sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil according to the embodiment of the present invention, the calibration method comprises the following steps:

[0062] T1: Replace the Fabry-Perot sensor in the test method with a standard microphone that can be used in oil;

[0063] T2: Repeat S1-S4 of the test method, corresponding to the standard microphone recording value Y' under different conditions in the test method;

[0064] T3: Considering the difference in attenuation effects of different sensors in transformer oil, the calibration coefficient k=(Y'-b) / Y, where Y is the response value of the optical demodulator measured under different conditions, b is a constant term determined by the calibration test, and the relationship between the Fabry-Perot sensor and the standard microphone includes but is not limited to a linear relationship.

[0065] T4: After calibration, the true value kY of the sensor’s sound pressure sensitivity is obtained.

[0066] Fig. 9The sensitivity directivity test diagram according to the embodiment of the present invention shows the normalized response value of the sensor in the angle range of 0° to 360°. In the test, the initial angle between the Fabry-Perot sensor and the sound source is set to 0°, and the angle between the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source is gradually adjusted in steps of 10° or 30°. At each angle, its response value is recorded and normalized, and the normalized reference value is the response value of the sensor at an angle of 0° and an initial distance. In this way, a sequence of normalized response values ​​at different angles is obtained, and the horizontal axis in the result diagram represents the angle, ranging from 0° to 360°, and the vertical axis represents the normalized response value. It can be clearly seen from the figure that the response of the sensor to different angles presents a specific trend of change. At some angles, the response value reaches a peak value, showing that the sensor has the highest sensitivity at this angle; while at other angles, the response value decreases, indicating that the sensor has a low sensitivity to these directions. Through this test diagram, the sensitivity directivity of the sensor can be effectively evaluated to help determine its optimal use conditions at different angles. This sensitivity directivity test diagram provides an intuitive data reference for the performance analysis of the sensor, so that the sensor can be optimally arranged according to the angle requirements in the application.

[0067] Based on the sensitivity directivity test chart, the same distance and different frequency charts can be plotted in the same coordinates to obtain the sensor's sensitivity curve based on frequency. In addition, the calibrated kY value can be plotted in the same coordinates to obtain the sensor's actual sound pressure sensitivity curve.

[0068] Obviously, the above embodiments are only examples for clear explanation and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description, and the changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A method for testing and calibrating the sensitivity directivity of a Fabry-Perot sensor in transformer oil, characterized in that: The device applicable to the method comprises: a host computer (1); a motor control module (2); an optical demodulator (3); a Fabry-Perot sensor (4); a transformer oil tank model (5); a sound-absorbing cotton (6); a sound source (7); a slide (8), which supports the precise movement and positioning of the Fabry-Perot sensor and the sound source; a signal generator (9), which is used to generate a stable sound source signal, wherein the slide (8) comprises a Fabry-Perot sensor transverse travel motor (801); a guide rail (802), wherein the internal thread cooperates with the external thread of the slide block (804), and is used to ensure the smooth movement of the slide block (804) in the slide rail groove (810); a Fabry-Perot sensor rotation motor (803), which is connected to the turntable (805) via the slide block (804); and a slider. (804); a turntable (805), connected to the Fabry-Perot sensor via a Fabry-Perot sensor connecting rod; a sound source rotating motor (806); a sound source lateral travel motor (807); a sound source fixing inverted Ω clamp (808), connected to the sound source connecting rod, used to stabilize the sound source; a connecting rod (809), including a Fabry-Perot sensor connecting rod and a sound source connecting rod, respectively used to connect the Fabry-Perot sensor and the sound source to their respective corresponding turntables; a slide rail groove (810); a limit block (811); a Fabry-Perot sensor fixing L-shaped inverted Ω clamp (812), connected to the Fabry-Perot sensor connecting rod, used to clamp the Fabry-Perot sensor (4); a slide holder (813), used to firmly clamp the slide on the transformer mailbox model (5); S1: The device is powered on, the initial frequency of the sound source is set to f0, and the initial distance between the sound source and the Fabry-Perot sensor is set to X0, where X0 is greater than the minimum distance and less than the maximum distance; S2: Controlling the Fabry-Perot sensor rotation motor (803) and the sound source rotation motor (806) so that the angle between the plane of the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source is 0°; S3: Control the Fabry-Perot sensor to rotate the motor (803) to change the turntable angle by 10° or 30° in steps, and the turntable angle is in the range of [0, 360°), thereby changing the angle between the sensitive diaphragm of the Fabry-Perot sensor and the sound source plane, and recording the response values ​​Yd00, Yd01, Yd02, ... measured by the optical demodulator at different angles when the spacing X0 is recorded; S4: Control the lateral travel motor (801) of the Fabry-Perot sensor and the lateral travel motor (807) of the sound source, change the distance X1, X2, ..., Xn between the sensitive diaphragm of the Fabry-Perot sensor and the plane of the sound source, repeat step S3, and record the response values ​​at different angles: Yd10, Yd11, Yd12,…; Yd20, Yd21, Yd22,…; Yd30, Yd31, Yd32,…; …； Ydn0, Ydn1, Ydn2,…; S5: Set the response value when the spacing is set to X0 and the angle is 0° as the upper limit, and calculate the normalized response of this test: Sd00=Yd00 / Yd00, Sd01=Yd01 / Yd00, Sd02=Yd02 / Yd00……; Sd10=Yd10 / Yd00, Sd11=Yd11 / Yd00, Sd12=Yd12 / Yd00…; Sd20=Yd20 / Yd00, Sd21=Yd21 / Yd00, Sd22=Yd22 / Yd00…; ……； Sdn0=Ydn0 / Ydn00, Sdn1=Ydn1 / Yd00, Sdn2=Ydn2 / Yd00,…; Based on the calculation results, draw the sensor directional sensitivity diagram; S6: Change the sound source frequency, repeat steps S2-S5, and draw a directional sensitivity diagram of the sensor at different frequencies.

2. The sensitivity directivity test and calibration method of the Fabry-Perot sensor in transformer oil according to claim 1, characterized in that: It also includes the calibration process, which includes: T1: Replace the Fabry-Perot sensor in the test method with a standard microphone that can be used in oil; T2: Repeat S1-S4 of the test method, corresponding to the standard microphone recording value Y' under different conditions in the test method; T3: Considering the difference in attenuation effects of different sensors in transformer oil, the calibration coefficient k=(Y'-b) / Y, where Y is the response value of the optical demodulator measured under different conditions, b is a constant term determined by the calibration test, and the relationship between the Fabry-Perot sensor and the standard microphone includes but is not limited to a linear relationship; T4: After calibration, the true value kY of the sensor’s sound pressure sensitivity is obtained.

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