Accelerometer
Strain gages are an excellent sensor for measuring accelerations, because of their inherent accuracy, sensitivity and responsiveness. A variety of cantilever and clamp supported beam elements have been used as the straining member because of their simplicity of analysis, design, manufacture and assembly. Negative aspects of beam structures are their sensitivity to transverse excitation and their low tolerance for damage during overloading. A perimeter supported diaphragm provides superior strain sensitivity while eliminating these two vulnerabilities. We have developed a robust accelerometer capable of measuring high levels of acceleration along a single axis of excitation, over a wide range of frequency using a diaphragm straining element. The diaphragm exhibits superior resistance to overload damage because of their biaxial stress distribution.
These accelerometers have been used to measure the behavior of foundation elements during construction and testing and are sold by our client as part of their instrumentation package. The accelerometer is attached to the side of a pile during driving and measures the dynamic signature of the stress wave. This mounting presents another problem not encountered in accelerometers subjected to tension/compression loading. The accelerometer is excited by the axial impact of the pile through a shear connection to the pile. Using the principles of tuned oscillators, we designed a mounting block that faithfully transmits the axial acceleration of the pile through the shear mounting and into the diaphragm accelerometer.
U.S. Patents have been issued to protect the intellectual property of both the accelerometer and the mounting block. The accelerometer and mounting block have been proven in driving piles in various field conditions over a two year period of operation.
This particular concept for accelerometers is well suited for obtaining the dynamic signature of impact processes used in manufacturing under unusual mounting conditions and hostile environments.