Measuring Explosions and Propellant Burns
Applications:
- Air Blast Measurement
- Underwater Explosion Measurement
- Peak and Total Impulse
- Explosive Research and Structural Loading
- Shock Tube or Closed Bomb Testing
- Wave Velocity and/or Time-of-arrival Determinations
- Explosive Component (e.g., Squib) Lot Acceptance
Pressure sensors with quartz, ceramic and tourmaline sensing elements are used for a wide variety of shock wave, blast and explosive testing. All of these applications require high frequency response and durability, ability to drive long cables and operate in adverse environments.
In applications involving long input cables to data acquisition systems, care must be exercised to assure the measurement system has adequate frequency response. Capacitance associated with the long cables can act as a low pass filter. Sensor output voltage, cable capacitance and constant current are factors to be considered. More current is required to drive higher voltages over longer cables. PCB® signal conditioners can be easily field-adjusted to provide up to 20 mA to drive long cables. Selecting a sensor to provide about 1 V full scale for the expected pressure to be measured, rather than 5V, will provide 5 times greater frequency response for a given current and cable length.
Most of our blast pressure sensors incorporate integral electronics and acceleration-compensating sensing elements, which provide a frequency-tailored, non-resonant response. Frequency tailored sensors have microsecond rise time and suppressed resonance to faithfully follow shock wave events without the characteristic "ringing" common in other sensors.
Model 132B38 is well suited for short wavelength acoustic and shock wave measurements associated with high-frequency projectile detection systems. . Incorporating a 1mm square sensing element and integral microelectronics in a 3mm housing, Model 132B38 has a very high sensitivity and microsecond response capable of identifying the bow and stern wave from a passing projectile. An internal 8 kHz high-pass filter eliminates low-frequency inputs.
Series 137B pencil probes are designed to measure shock waves caused from explosions in air. Series 137B quartz, free-field, ICP® blast pressure probes have a unique pencil shape that allows the shock wave to progress smoothly across the sensor, providing distortion free measurements. The 137B series is available in single and dual-sensing element housings.
Model 134A24 is a unique non-resonant sensor is designed for instantaneous, reflected (face-on) shock wave pressure measurements in dry environments. A shock wave pressure impacting the very thin tourmaline crystal which operates into a silver alloyed "pressure bar", eliminates sensor structure response. The sensor has a 0.2-microsecond rise time. The sensor diaphragm end is coated with a conductive silver epoxy.
Model 138A10 measures shock wave pressures associated with underwater explosion testing. It is structured with a volumetrically sensitive tourmaline crystal, suspended and sealed in an insulating, oil-filled vinyl tube. They have integral microelectronics. These underwater shock wave sensors provide a clean, non-resonant, high-voltage output through long cables in adverse underwater environments. They can be supplied with a sealed cable of appropriate length, ready to operate. Two physical configurations are available.