Novel double-crystal-configuration overpressure sensor with vibration compensation function

Abstract

The invention discloses a novel double-crystal-configuration overpressure sensor with a vibration compensation function. Based on a vibration interference arrival end compensation thought, a set of compensation sensitive element assembly is added on the basis of a traditional piezoelectric pressure sensor, a compensation sensitive element which is the same as a sensor main sensitive element in material and size and opposite in placement direction is adopted, and charges generated by vibration impact are sensed synchronously; the method is used for counteracting vibration spurious charges generated when a main sensitive element is interfered by flat plate vibration, compensation of vibration interference is achieved, and the test precision of shock wave pressure signals is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of explosion power experimental testing, and relates to an explosion shock wave pressure measurement sensor, in particular to a novel overpressure sensor with a dual-crystal configuration having a vibration compensation function. Background Art

[0002] The damage effect of an explosion shock wave is jointly determined by the peak overpressure and impulse. Short-time pulse damage mainly depends on the peak overpressure, while long-time pulse damage mainly depends on the impulse. This requires the pressure measurement sensor to maintain high measurement accuracy throughout the shock wave action period to accurately reflect the dynamic changes of these two effects. Shock wave pressure sensors can be classified into capacitive, resistive, and piezoelectric types according to their working principles. Among them, piezoelectric pressure sensors have good high-frequency response characteristics, fast response speed, and stable performance, and have a wide range of application scenarios.

[0003] The sensitive element of a piezoelectric pressure sensor is a piezoelectric material such as quartz, ceramic, or polymer. When pressure acts on the sensitive element, charges with equal amounts and opposite polarities will be generated on its upper and lower surfaces, and the magnitude of the charge quantity is linearly related to the pressure it receives. An ideal shock wave pressure sensor is a single-input single-output system. However, in actual tests, the environment where the sensor is located also contains various interferences, such as noise, pulses, shock vibrations, temperature, etc. The shock wave pressure and various interference factors will directly act on the sensitive element, resulting in the sensor outputting charges generated by various interference factors while outputting charges generated by the shock wave pressure. During the wall reflection pressure test process, the sensor needs to be fixed on the installation plate. The installation plate generates axial vibration under the shock wave pressure, and the axis direction of the sensitive element of the wall pressure sensor is parallel to the vibration direction of the structure or the installation plate. This vibration interference will cause axial compression deformation of the sensor, generating vibration parasitic output, which interferes with the test of the shock wave pressure signal. Summary of the Invention

[0004] Aiming at the problems that the piezoelectric pressure sensor has poor low-frequency response characteristics, is sensitive to vibration acceleration loads, is easily affected by the interference of the flat plate vibration and generates vibration parasitic output, which affects the test effect of the shock wave pressure signal, the present invention provides a novel overpressure sensor with a dual-crystal configuration having a vibration compensation function, which can effectively compensate the axial vibration interference of the installation plate during the wall reflection shock wave pressure test and improve the shock wave pressure measurement accuracy.

[0005] The novel overpressure sensor with a dual-crystal configuration having a vibration compensation function of the present invention adds a compensation sensitive element assembly on the basis of the traditional piezoelectric pressure sensor; the compensation sensitive element assembly includes: a compensation sensitive element, a compensation mass block, a positioning sleeve, and a metal sleeve;

[0006] Among them, the compensation sensitive element is located on the core electrode and is collinear with the main sensitive element and the core electrode; the material and size of the compensation sensitive element are the same as those of the main sensitive element, and the placement direction is opposite to that of the main sensitive element;

[0007] The compensation mass block is located above the compensation sensitive element; the material and bottom surface size of the compensation mass block are the same as those of the main mass block;

[0008] The positioning sleeve is located on both sides of the compensation mass block and the compensation sensitive element, and is used to fix the compensation mass block and the compensation sensitive element and insulate them from the metal sleeve;

[0009] One end of the metal sleeve is open and wraps around the positioning sleeve; the open end of the metal sleeve faces downward and contacts the core electrode; there is a gap between the metal sleeve and the compensation mass block; the main sensitive element, the main mass block, and the elastic element are placed in sequence above the metal sleeve; the main mass block is connected to the compensation mass block through a wire.

[0010] Preferably, the gap between the metal sleeve and the compensation mass block is 0.5 - 3 mm.

[0011] Preferably, the thickness ratio of the elastic element, the main mass block, and the compensation mass block is 1:2:2.

[0012] Preferably, the elastic element is 0.6 - 1.4 mm thick, and the main / compensation mass block is 1.5 - 2.5 mm thick.

[0013] Preferably, the compensation sensitive element and the main sensitive element are made of quartz crystal, lithium niobate, lead zirconate titanate, barium titanate, potassium niobate, or lithium tantalate.

[0014] Preferably, the compensation mass block and the main mass block are made of phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti - 6Al - 4V titanium alloy, AISI 1045 medium carbon steel, or AISI 4140 alloy steel.

[0015] Preferably, the positioning sleeve is made of polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylene propylene copolymer, polyetheretherketone, polyimide, or polychlorotrifluoroethylene.

[0016] Preferably, the elastic element can be made of 2Cr13 stainless steel, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti - 6Al - 4V titanium alloy, AISI 1045 medium carbon steel, AISI 4140 alloy steel.

[0017] Preferably, the core electrode can be made of phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti - 6Al - 4V titanium alloy, AISI 1045 medium carbon steel, AISI 4140 alloy steel.

[0018] Preferably, the sensitivity of the double-crystal overpressure sensor is calibrated as follows:

[0019] Place two identical double-crystal overpressure sensors to be calibrated at a certain distance along the shock wave propagation direction; after connecting the double-crystal overpressure sensors to be calibrated to a charge amplifier, connect them to an oscilloscope;

[0020] Load the shock wave;

[0021] Calculate the sensitivity S of the double-crystal overpressure sensor as:

[0022]

[0023] where Q is the electric charge generated by the double-crystal sensor, V is the voltage value of the oscilloscope, A is the charge amplifier multiple; ΔP is the average overpressure of the shock wave, where P0 is the atmospheric pressure; k is the adiabatic index of the medium; M is the Mach number, where C0 is the local speed of sound; D is the average speed of the shock wave between the two double-crystal sensors, where ΔS is the distance between the two double-crystal sensors; Δt is the time interval between the two double-crystal sensors starting to jump.

[0024] Beneficial effects:

[0025] Based on the idea of vibration interference arrival end compensation, the present invention adds a set of compensation sensitive element components on the basis of the traditional piezoelectric pressure sensor. By using compensation sensitive elements with the same material and size as the main sensitive element of the sensor and opposite placement directions, the electric charge generated by the vibration impact is synchronously sensed to cancel the vibration parasitic charge generated by the interference of the main sensitive element by the flat vibration, realizing the compensation of the vibration interference and improving the test accuracy of the shock wave pressure signal.

[0026] The acceleration sensitivity can be eliminated by controlling the thickness ratio of the compensation mass block to the main mass block and the elastic element. Brief description of the drawings

[0027] Figure 1 It is a schematic diagram of the compensation design principle of the multi-input multi-output system of the novel overpressure sensor with a double-crystal configuration having a vibration compensation function according to the present invention.

[0028] Figure 2 It is a schematic diagram of the structural design of the novel overpressure sensor with a double-crystal configuration having a vibration compensation function according to the present invention.

[0029] Figure 3 It is a comparison diagram of the shock wave overpressure curves measured by the overpressure sensor, the control group single-crystal sensor, and the PCB pressure sensor according to the present invention.

[0030] Figure 4 It is the impact acceleration curve measured by the acceleration sensor. Specific implementation mode

[0031] The present invention will be described in detail below in conjunction with the accompanying drawings and by way of examples.

[0032] The present invention provides a novel overpressure sensor with a dual-crystal configuration having a vibration compensation function.

[0033] The schematic diagram of the principle of the present invention is as Figure 1 shown. Adopting the idea of vibration interference arrival end compensation, a set of compensation sensitive element components is added on the basis of a traditional piezoelectric pressure sensor. By using compensation sensitive elements with the same material and size as the main sensitive element of the sensor and opposite placement directions, the charges generated by vibration impacts are synchronously sensed, and the vibration impacts received by the main sensitive element are offset, realizing the compensation for vibration interference.

[0034] The structural schematic diagram of the sensor of the present invention is as Figure 2 shown. On the basis of a traditional piezoelectric pressure sensor (the traditional piezoelectric pressure sensor includes a main mass block, a main sensitive element, an elastic element, insulating sleeve 1, an upper housing, a lower housing, a core electrode, insulating sleeve 2, and a pressure-bearing pad), a set of compensation sensitive element components is added; the compensation sensitive element components include: a metal sleeve, a positioning sleeve, a compensation mass block, and a compensation sensitive element.

[0035] The compensation sensitive element is adhesively connected to the core electrode, and the compensation sensitive element, the main sensitive element, and the core electrode are on the same straight line; the material and size of the compensation sensitive element are the same as those of the main sensitive element, and the placement direction is opposite to that of the main sensitive element;

[0036] The compensation mass block is located above the compensation sensitive element; the material and bottom surface size of the compensation mass block are the same as those of the main mass block; the compensation mass block and the main mass block are also connected by a wire;

[0037] The positioning sleeve is located on both sides of the compensation mass block and the compensation sensitive element, used to fix the compensation mass block and the compensation sensitive element, and also used for insulation between the compensation mass block / compensation sensitive element and the metal sleeve;

[0038] The lower end of the metal sleeve is open and wraps around the positioning sleeve, and the compensation sensitive element, the compensation mass block, and the positioning sleeve are located inside the metal sleeve; the open end of the metal sleeve contacts the core electrode; there is an air gap between the metal sleeve and the compensation mass block; the upper end of the metal sleeve is closed, and the main sensitive element, the main mass block, and the elastic element are sequentially placed above the metal sleeve;

[0039] The piezoelectric pressure sensor is an active sensor. When the sensitive element is under the action of an external force, equal amounts of positive and negative charges are generated on its upper and lower surfaces respectively. It is necessary to form a circuit for the charges on the upper and lower surfaces and convert them into corresponding voltage signals through signal processing. Generally, the housing of the sensor is positively charged and the core electrode is negatively charged, and insulation is carried out through an insulating sleeve and a pressure-bearing cushion block. In the present invention, positive charges are generated on the upper surface of the main sensitive element and negative charges are generated on the lower surface, while the electrical properties of the upper and lower surfaces of the compensation sensitive element are opposite to it.

[0040] The main sensitive element is connected to the compensation sensitive element through a metal sleeve and a core electrode, and a wire is used to connect the compensation mass block and the main mass block; the negative charges generated on the lower surface of the main sensitive element due to vibration acceleration are offset by the positive charges generated on the lower surface of the compensation sensitive element through the metal sleeve and the core electrode, and the positive charges generated on the upper surface of the main sensitive element due to vibration acceleration are offset by the negative charges generated on the upper surface of the compensation sensitive element through the main mass block, the wire and the compensation mass block, forming a complete compensation circuit.

[0041] When the shock wave pressure acts on the elastic element, the pressure of the air fluid is converted into force and transmitted downward, and the force propagates in the form of a stress wave in the sensor. When the stress wave reaches the main sensitive element, it causes charge output; and due to the existence of an air gap between the metal sleeve and the compensation mass block, the stress transmitted from the metal sleeve into the air is very small and can be almost ignored, so that the charge output of the compensation sensitive element caused by the shock wave is almost 0. At the same time, the installation plate vibrates violently under the action of the shock wave pressure, and the vibration is input into the sensor in the form of acceleration. Ideally, all components of the sensor have the same acceleration, so that the main sensitive element and the compensation sensitive element generate the same inertial force. The main sensitive element and the compensation sensitive element are quartz crystals with exactly the same material and size. Under the action of the same inertial force, charge outputs with equal magnitudes and opposite electrical properties are generated. The charge output of the compensation sensitive element caused by vibration acceleration can completely offset the charge output of the main sensitive element caused by vibration acceleration, realizing the compensation for vibration interference.

[0042] Among them, the compensation sensitive element and the main sensitive element can adopt piezoelectric organic materials and polymers such as quartz crystal, lithium niobate, lead zirconate titanate, barium titanate, potassium niobate, and lithium tantalate;

[0043] The compensation mass block and the main mass block can adopt phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel or AISI 4140 alloy steel;

[0044] The metal sleeve is made of a metal material with conductive ability, such as copper, etc.;

[0045] The positioning sleeve can adopt polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylenepropylene, polyetheretherketone, polyimide or polychlorotrifluoroethylene;

[0046] The elastic element can be made of 2Cr13 stainless steel, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel, or AISI 4140 alloy steel;

[0047] The insulating sleeve material can be made of polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylene-propylene copolymer, polyether ether ketone, polyimide, or polychlorotrifluoroethylene;

[0048] The core electrode can be made of phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel, or AISI 4140 alloy steel.

[0049] In order to achieve maximum compensation for vibration interference while ensuring the accuracy of peak overpressure in the sensor, the thickness ratio of the elastic element, the main mass block, and the compensation mass block is preferably 1:2:2. Preferably, the elastic element has a thickness of 0.6 - 1.4 mm, and the main / compensation mass block has a thickness of 1.5 - 2.5 mm. The air gap is preferably 0.5 - 3 mm.

[0050] The following is a specific description in conjunction with an embodiment. In this embodiment, the main sensitive element and the compensation sensitive element are made of quartz crystal, the elastic element and the housing are made of 2Cr13 stainless steel, the mass block is made of phosphor bronze, the positioning sleeve and the insulating sleeve are made of polytetrafluoroethylene, the pressure-bearing pad is made of fiberglass, and the core electrode and the flat gasket are made of phosphor bronze. The specific material parameters are shown in Table 1.

[0051] When the thickness of the elastic element is 1 mm, the thickness of the main mass block is 2 mm, and the thickness of the compensation mass block is 2 mm, the sensor can achieve maximum compensation for vibration interference while ensuring the accuracy of peak overpressure.

[0052] Table 1 Material Model Parameters

[0053]

[0054] Remove the compensation sensitive element assembly in the novel overpressure sensor with a double-crystal configuration to make a single-crystal overpressure sensor that is exactly the same as the double-crystal overpressure sensor but does not have a compensation function. Use the single-crystal overpressure sensor and the PCB pressure sensor as a comparison group, and set an acceleration sensor at the same time. That is: install the PCB pressure sensor, the acceleration sensor, the double-crystal sensor of the present invention, and the single-crystal sensor with the compensation function removed on the installation plate. The measured shock wave overpressure curve is as Figure 3As shown. It can be seen that: within the time range of 0.5 - 3 ms, the shock wave overpressure curves of the PCB pressure sensor and the single crystal sensor basically coincide, indicating that the shock wave pressures and vibration states received by the three sensors are basically the same, while the shock wave overpressure curve of the double crystal sensor is significantly lower than that of the PCB pressure sensor and the single crystal sensor during this time period. The only difference between the double crystal sensor and the single crystal sensor lies in the compensation sensitive element. Obviously, the reduction of the shock wave overpressure curve of the double crystal sensor under the action of the same shock wave pressure and vibration load is closely related to the function of the compensation sensitive element. From Figure 4 the acceleration curve, it can be seen that within 1 - 3 ms, the sensor generates a large reverse acceleration, and the shock wave overpressure curve of the double crystal sensor is significantly lower than that of the PCB sensor and the single crystal sensor during this time period. Thus, it can be known that the double crystal sensor compensates for the parasitic output caused by the vibration of the installation plate. Since the acceleration drops significantly after 3 ms, the overpressure curve of the double crystal sensor after 3 ms is not much different from that of the single crystal sensor and the PCB pressure sensor, indicating that the novel overpressure sensor with a double crystal configuration of the present invention can effectively measure the overpressure and effectively compensates for the vibration interference.

[0055] Before the test, a calibration system can be used to calibrate the sensitivity of the double crystal sensor of the present invention prepared and the single crystal sensor used as a control group. The average value of the sensitivity is taken as the true sensitivity of the sensor by calibrating multiple times.

[0056] The calibration system consists of two identical sensors to be calibrated, a charge amplifier, and an oscilloscope. The double crystal sensor and the single crystal sensor to be calibrated are charge-type shock wave pressure sensors and need to be used in conjunction with a charge amplifier. The charge amplifier can amplify the weak charge signal output by the sensor to be calibrated and convert it into a voltage signal, and at the same time, it can convert the high-impedance output of the sensor to be calibrated into a low-impedance output. Taking the double crystal sensor as an example, the single crystal sensor has the same calibration process. The sensor sensitivity calibration process is as follows:

[0057] Air compression shock waves are generated by a shock tube for loading. The two double crystal sensors to be calibrated are 0.505 m apart to generate a starting time difference. The shock tube consists of four parts: a high-pressure section, a diaphragm, a locking mechanism, and a low-pressure section, and is driven by high-pressure nitrogen.

[0058] The average speed of the shock wave between the two double crystal sensors:

[0059]

[0060] In the formula: ΔS is the distance between the two double crystal sensors; Δt is the time interval between the starting jumps of the two double crystal sensors.

[0061] The Mach number of the shock wave is:

[0062]

[0063] Where: D is the average shock wave velocity between two pairs of crystal sensors; C0 is the local speed of sound, and T is the ambient temperature.

[0064] Based on the basic relationship of shock waves, the average shock overpressure can be obtained:

[0065]

[0066] Where: ΔP is the average shock wave overpressure; P0 is the atmospheric pressure; k is the adiabatic index of the medium (generally air), k = 1.4; M is the Mach number.

[0067] The electric charge Q generated by the double crystal sensor:

[0068]

[0069] Where: V is the voltage value of the oscilloscope, and A is the charge amplifier multiple. Therefore, the sensitivity of the double crystal sensor is:

[0070]

[0071] Taking the average value of the sensitivity after multiple calibrations is the true sensitivity of the double crystal sensor.

[0072] In summary, the above is only a preferred embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A novel overpressure sensor with dual crystal configuration and vibration compensation function, comprising: The main mass block, the main sensitive element, the elastic element, the insulating sleeve, the shell, the core electrode and the pressure-bearing pad are characterized in that they also include: a compensation sensitive element assembly; the compensation sensitive element assembly includes: a compensation sensitive element, a compensation mass block, a positioning sleeve and a metal sleeve; The compensating sensitive element is located on the core electrode and is in the same straight line with the main sensitive element and the core electrode; the material and size of the compensating sensitive element are the same as those of the main sensitive element, and the placement direction is opposite to that of the main sensitive element; The compensation mass block is located above the compensation sensitive element; the material and bottom surface size of the compensation mass block are the same as those of the main mass block; The positioning sleeve is located on both sides of the compensation mass block and the compensation sensitive element, and is used to fix the compensation mass block and the compensation sensitive element and insulate them from the metal sleeve; One end of the metal sleeve is open and wrapped around the positioning sleeve; the open end of the metal sleeve is downward and in contact with the core electrode; a gap is left between the metal sleeve and the compensation mass block; the main sensitive element, the main mass block and the elastic element are placed above the metal sleeve in sequence; the main mass block is connected to the compensation mass block through a wire.

2. The overpressure sensor according to claim 1, characterized in that: The gap between the metal sleeve and the compensation mass block is 0.5-3mm.

3. The overpressure sensor according to claim 1, characterized in that: The thickness ratio of the elastic element, the main mass block and the compensation mass block is 1:2:

2.

4. The overpressure sensor according to claim 3, characterized in that: The thickness of the elastic element is 0.6-1.4 mm, and the thickness of the main / compensation mass block is 1.5-2.5 mm.

5. The overpressure sensor according to any one of claims 1 to 4, characterized in that: The compensation sensitive element and the main sensitive element adopt quartz crystal, lithium niobate, lead zirconate titanate, barium titanate, potassium niobate or lithium tantalate.

6. The overpressure sensor according to any one of claims 1 to 4, characterized in that: The compensation mass block and the main mass block are made of phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel or AISI4140 alloy steel.

7. The overpressure sensor according to any one of claims 1 to 4, characterized in that: The positioning sleeve is made of polytetrafluoroethylene, polyvinylidene fluoride, polyperfluoroethylene propylene, polyetheretherketone, polyimide or polychlorotrifluoroethylene.

8. The overpressure sensor according to any one of claims 1 to 4, characterized in that: The elastic element can be made of 2Cr13 stainless steel, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel, or AISI 4140 alloy steel.

9. The overpressure sensor according to any one of claims 1 to 4, characterized in that: The core electrode can be made of phosphor bronze, 304 stainless steel, 316 stainless steel, 6061 aluminum alloy, Ti-6Al-4V titanium alloy, AISI 1045 medium carbon steel, or AISI 4140 alloy steel.

10. The overpressure sensor according to claim 1, characterized in that: The sensitivity of the dual crystal overpressure sensor is calibrated as follows: Two identical dual-crystal overpressure sensors to be calibrated are placed at a certain distance along the propagation direction of the shock wave; the dual-crystal overpressure sensors to be calibrated are connected to a charge amplifier and then to an oscilloscope; Loading shock wave; The sensitivity S of the dual crystal overpressure sensor is calculated as: Where Q is the charge generated by the dual crystal sensor, V is the voltage value of the oscilloscope, A is the charge amplifier multiple; ΔP is the average value of the shock wave overpressure, Where P0 is the atmospheric pressure; k is the adiabatic index of the medium; M is the Mach number, Where C0 is the local sound velocity; D is the average velocity of the shock wave between the two crystal sensors. Wherein, ΔS is the distance between the two dual-crystal sensors; Δt is the time interval between the two dual-crystal sensors taking off.

Images