1. Field of the Invention
The present invention relates a ballistics pressure transducer and more particularly, is directed to a miniaturized piezoelectric pressure transducer used for measuring pressure characteristics in gun weapon tubes during the propellant ignition and burning process of ordnance projectiles.
2. Description of the Prior Art
My U.S. Pat. No. 4,621,519 relates to the model T8 ballistics pressure transducer and is briefly described in the present invention. Although the patented model T8 pressure transducer design has proven to be very reliable in a wide variety of applications, recent development in the higher performance ammunition components and propellants have made it necessary to severely restrict the size of the pressure ports that can be drilled in a gun tube in order to minimize stress concentrations. The recent requirement for measuring chamber pressures in gun tubes with concentric recoil systems has also limited the size of pressure transducers because no part of the transducer can extend beyond the outside surface of the gun tube. There is a limit to which the mode T8 design can be miniaturized and still maintain the required structural integrity; therefore a new design had to be developed.
Prior to the present invention, the best pressure transducer available for chamber pressure-time measurements in the higher performance weapon systems was the Kistler model 6211 miniaturized quartz transducer. The present disclosure describes the Kistler model 6211 and compares it with the two embodiments; namely, the models E30M and E30MA.
In the comparison tests, there has been noted some significant design problems which adversely affects the quality and accuracy of the pressure data. Some of the more significant design problems include:
a. The quartz pressure sensing element is not electrically insulated from ground which can allow stray electrical signals to be superimposed on the pressure data and be interpreted as pressure pulses. This design also makes it very difficult to eliminate electrical noise caused by ground loops. The pressure sensing element in the present invention is electrically insulated from ground. PA1 b. The output sensitivity is approximately one third that of the E30M and E30MA models described in the present invention which results in a considerably lower signal-to-noise ratio. PA1 c. The amount of torque applied in mounting the model 6211 transducer is very critical. The output sensitivity can change by several percent if an excessive amount of torque is applied. It also requires retorqueing after every few rounds which can cause significant test delays if the gun tube has to be removed from its mount to gain access to the transducer. The present invention is not torque sensitive. PA1 d. The maximum pressure limit on the model 6211 transducer is approximately 105K psi and there are already measurement requirements in the field exceeding this limit. The present invention has been tested up to approximately 125K psi. The maximum pressure limit has not been determined.