Accelerometer, Fiber Optic, Photoelastic
A Fiber Optic Photoelastic Accelerometer has been designed and developed, which operates with a force transducer made from an optically birefringent material. Signal measurements are made by Photoelastic techniques using an LED as an incoherent light source. The Accelerometer has a sensitivity of 2 V/g’s, a resolution of 2.5 mg’s for a frequency range from 0 to 600 Hz; and a linear amplitude range of 0 to 5 g’s.
The Accelerometer housing is a hermetically sealed aluminum case 41 mm x 35 mm x 20 mm with the force transducer mounted inside. The sensing element is a Photo elastic material located between two crossed linear optical polarizes. The 20 gram copper seismic mass has support elements made of stainless steel shim stock. The remaining support structure is an aluminum alloy.
The radius of the seismic mass cylindrical surface is 0.5 mm at the point of contact. A preload is applied to the Photoelastic sensing element. Optical access to the transducer is provided by two 200µm diameter multimode Fiber Optics. Fiber Optic ferrules holds the Fiber Optics in place. A 0.5 pitch GRIN lens collimates the light source increasing the optical coupling efficiency.