Patent ID: 7035167

Claim:
A seismic sensor for sensing seismic activity, comprising a case; a pre-charged, non-conductive membrane located between two plates that form a capacitor and accommodated inside said case, with one of said plates being immovable relative to said case and the other of said plates being movable relative to said one plate under the action of seismic activity of a medium in which the sensor is located, so that said capacitor produces an electrical signal responsive to the seismic activity, said movable plate being formed as a single uninterrupted flexible diaphragm extending transversely over a total transverse cross-section of said case, so that under the action of seismic activity when the sensor moves as a whole said diaphragm oscillates as a whole relative to said immovable plate; and a mass increasing element associated with said movable plate so as to increase mass of said diaphragm and therefore enhance oscillations of said diaphragm under the action of the seismic activity, said mass increasing element being formed as a single lug which is attached to said single uninterrupted flexible diaphragm in a center of said single uninterrupted flexible diaphragm and is displaceable together with said flexible diaphragm in response to the movement of the sensor as a whole under the action of seismic activity.