Shock isolated accelerometer

This paper presents a novel concept for isolating an accelerometer from large, potentially damaging, transient accelerations. It consists of a piston, bore, and a present frictional force between the two. The accelerometer is mounted on the piston. The piston will displace relative to the bore when the input force to the bore is equal to or greater than the frictional force. By knowing the total piston mass and frictional force between it and the bore, an upper limit to the transmitted acceleration is defined. This clipping acceleration level can then be set to protect the transducer from overranging. Initial tests have successfully clipped 80kg, 70 micron sec duration, input accelerations down to an average level of 20kg. It is shown that once the piston stops sliding within the bore, the integrated accelerometer signal will give the true velocity of the gauge package, and the doubly integrated accelerometer signal will give the true displacement minus the relative displacement between the piston and bore. Methods of controlling the accelerometer and gauge package resonances, excited through shock input, are being developed.