Publish Time: 2025-07-25 Origin: Site
Free Field “Pencil-Type” Explosion Dynamic Pressure Sensor Instruction Manual
1.Product Overview
This sensor utilizes the piezoelectric effect of piezoelectric materials to convert measured pressure into electrical signals. It features acceleration compensation functionality. The quartz sensitive element is integrated with microelectronic circuits for long cable drive, offering excellent consistency and thermal stability. With a wide frequency range, fast dynamic response, and good temperature characteristics, it is suitable for dynamic pressure testing.
2.Product Features
① Sufficiently large frequency response to reliably reflect all subtle changes in pressure;
② Infinitely small size to avoid disturbing the transient flow field of an explosion shock wave;
③ Sensitive only to the pressure characteristics being measured, and insensitive to irrelevant signals such as acceleration, electromagnetic, or optical environmental factors;
④ High sensitivity coefficient to the measured quantity;
⑤ Linear response to extremely small or extremely large input signals;
⑥Excellent stability.
3.Layout of the shock wave testing system during open-field explosion experiments
Ground Explosion Shock Wave Test System Layout
There are two types of shock wave tests conducted during explosions in open areas: airborne shock wave tests and ground shock wave tests. In the case of near-ground explosions in the air, since the Mach wave front is not a flat plane, differences in the height of the airborne measurement points and the installation angle can lead to significant errors. Therefore, during airborne shock wave field tests, the height of the sensors should be above the three wave points.
1)When measuring the pressure of a reconstructed explosion shock wave field (skimming method), the sensitive surface of the sensor must be aligned with the direction of the shock wave's movement and perpendicular to the wavefront. The sensor unit should minimize disturbance to the shock wave field. The structure of the intelligent sensor unit should be capable of adjusting the orientation of the sensor's sensitive surface according to the propagation direction of the shock wave to measure the overpressure of the incident shock wave.
2)When measuring the reflected pressure of the shock wave, the sensor's sensitive surface should be perpendicular to the direction of shock wave propagation (parallel to the wavefront). During ground testing, the sensor's sensitive surface should be flush with the ground, and the deployment location is best within the Mach wave region. During direct reflection shock wave testing, the sensor should be positioned directly below the explosion source. Typically, steel plates or precast plates are laid beneath the explosion source to securely fix the intelligent sensor unit in place; otherwise, the intelligent sensor unit directly below the explosion source may be blown away during the explosion. The specific layout diagram is shown in the figure.
4.Project Real Scenery
IEPE type
PE type
6.Sensor selection
1)Selection between IEPE-type and charge-type sensors
Piezoelectric pressure sensors are categorized into IEPE-type and charge-type. IEPE-type sensors feature built-in amplification circuits, offering convenience and cost-effectiveness. However, their drawbacks include greater susceptibility to damage compared to charge-type sensors, and limited flexibility in measurement range (dynamic range) due to output voltage constraints. Charge-type sensors, when used with a charge amplifier, offer a larger dynamic range and higher reliability. Users can select the appropriate type based on the above considerations and their specific requirements.
2)Selection of Piezoelectric vs. Piezo-resistive Sensors
Piezoelectric pressure sensors are widely used due to their fast response time, good temperature characteristics, high linearity, low drift, excellent sealing properties, long-term reliability, and ability to withstand harsh environments. Piezo-resistive sensors, however, are sensitive to light and temperature. If such sensors are used in explosive testing conditions, light and temperature can alter the sensor's sensitivity (referring to the calibrated sensitivity under normal environmental conditions).
3)Selecting Sensors with Appropriate Resonant Frequencies
Explosion pressure testing involves high frequencies, which requires the sensor's own resonant frequency to be sufficiently high to avoid resonance. When in use, the selected sensor's resonant frequency should exceed the explosion frequency being tested. If the sensor's resonant frequency is insufficient, useful signals may be amplified by resonance, making it impossible to read the true amplitude of the explosion waveform and affecting the accuracy of the test signal. As shown in the figure below, the left side depicts the standard explosion waveform, while the right side illustrates the resonance phenomenon caused by an insufficient sensor resonant frequency.
7.Installation and use, supporting instruments, self-inspection and maintenance
1) Installation
Mounting bracket materials: steel, steel pipes, galvanized surface, painted; a cushioning layer is provided between the sensor and the clamping fixture; the bracket height must be adjustable between 1.2m and 2m; the outer diameter of the fixed section of the steel pipe bracket is between 30mm and 5mm; the outer diameter of the telescoping section of the steel pipe matches that of the fixed steel pipe, but must be no less than 20mm to ensure the telescoping section does not shake; The bottom of the bracket is equipped with a retractable tripod support to ensure the stability of the entire bracket.
2)System grounding
Pressure sensors can be used for reflected wave overpressure testing. Many products come with threads for easy installation. When installing, the sensor's sensitive surface should be flush with the mounting component. The sensor can also be installed using a clamping method, with the clamping area made of insulating material, such as rubber, to improve waveform quality while achieving single-point grounding. Some users may use mounting blocks for adaptation. We recommend using insulating material when the explosion equivalent is not large, as it provides both vibration resistance and insulation.
Our company's free-field sensor mounting brackets use insulating materials as padding at the clamping points and are secured with screws, achieving single-point grounding. Since the mounting support rods for free-field sensors have a certain height, the connections from the ground to each component must have sufficient strength to avoid interference caused by vibration or other factors.
The installation methods discussed above and improvements in test waveforms are interrelated; users must continuously experiment to refine installation techniques.
3)Supporting instruments
(1) In the field of explosions, amplifiers are used to connect sensors and signal analyzers. Selecting an amplifier with the appropriate frequency is critical, as failure to do so can significantly impact test accuracy. Note that the instrument's frequency response should ideally be approximately twice the test frequency (since the instrument's rated frequency is ±3 dB), ensuring the most accurate representation of the entire explosion waveform. Charge-type sensors are connected to charge amplifiers, while IEPE sensors are connected to wide-band constant-current adapters. For usage and calculation guidelines, refer to the relevant user manuals. Pressure value calculations primarily follow the instructions in the subsequent instrument manuals.
(2) Data collector (signal analyzer)
The collector is mainly used for testing and analyzing explosion and blast shock waves with high-frequency pressure sensors. It can be combined into a distributed explosion testing system for large-scale explosion testing. It has multiple channels, with a sampling rate of 20M per channel. To ensure testing accuracy, it is recommended that the sampling frequency of the data collector be more than 10 times higher than the test frequency.
4)Sensor detection
The calibration of piezoelectric pressure sensors is divided into dynamic calibration and quasi-static calibration. Quasi-static calibration tests the low-frequency amplitude linearity and sensitivity of the sensor. Dynamic calibration involves applying a high-frequency excitation signal to the sensor being calibrated, obtaining the response curve of the sensor through high-speed data acquisition, and comparing it with a standard sensor to obtain the dynamic sensitivity and dynamic response curve of the sensor. In theory, the dynamic and static sensitivities of a dynamic pressure sensor should be consistent. However, in practice, due to factors such as sensor structure, assembly process, piezoelectric material, and installation, the dynamic and static sensitivities of the sensor may not be consistent. Therefore, the sensor should provide both dynamic and static sensitivities at the time of manufacture to minimize testing errors for users in different application scenarios.
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