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Reference <br />• ~ <br />a. Geophone Operation <br />Functionally a geophone sensor is a coil of wire suspended around a magnet. The magnet is free to <br />move in a field of magnetic fluz lines. By Lenzs' Law, induced voltage is proportional to the speed <br />at which flux lines are unversed. Induced coil voltage is therefore proportional to the relative <br />velocity of the coil to the magnet. In practice, i[ does not matter whether the coil or the magnet <br />moves. Only the motion and speed relative to each other are important. <br />• <br />COII <br />I <br />induced <br />voltage direction of motion of magnet <br />+~ ~--~ <br />relative to coil <br />~-magnet <br />Figure 5.5 Geophone Sensor Operation. <br />Geophone sensor. specifications give a number known as the Intrinsic Voltage Sensitivity. It is the <br />coil voltage induced for a given coil versus magnet speed with units of V(n/s. In seismic <br />applications, the magnet is moved by the blast energy because it is coupled to the particles of the <br />surrounding Certain. The coil, because of its inertia, does not move and the resulting magnet versus <br />coil motion induces a voltage which is proportional to particle velocity. <br />b. Instantel Standard Transducer <br />Instantel offers a 2 to 300 Hz standard transducer in a round package. The vansducer maybe <br />installed on a floor, wall, or ceiling using a variety of installation procedures including ground <br />spikes, burying, mounting rod, or optional leveling plate with leveling feet and integrated bubble <br />level. The figure below includes an Instantel Standazd Transducer (a) and a Standard Transducer <br />with leveling plate (b). <br />• <br />Blasn~Iate III Operator Manual 5-5 <br />