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<br />Reference <br />• a. Geophone Operation <br />Functionally a geophone sensor is a coil of wire suspended azound a magnet. The magnet is free to <br />move in a field of magnetic flux lines. By Lenzs' Law, induced voltage is proporrional to the speed <br />at which flux lines are traversed. Induced coil voltage is therefore proportional to the relati.•c <br />velocity of the coil to the magnet. In practice, it does not matter whether the coil or the magnet <br />moves. Only the motion and speed relative to each other aze important. <br />f~ <br />COII <br />t <br />induced <br />voltage direction of motion of magnet <br />1 ~-~ <br />relative to coil <br />~ magnet <br />Figure 5.5 Geophone Seasor Operation. <br />Geophooe sensor specifications give a number known az the Intrinsic Voltage Sensitivity. It is the <br />coil voltage induced for a given coil versus magnet speed with units of Vlin/s. In seismic <br />applications, the magnet is moved by the blast energy because it is coupled to the particles of the <br />surtounding terrain. The coil, because of irs 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 transducer may be <br />installed on a floor, wall, or ceiling using a variety of installation procedures including ground <br />spikes, burying, mounting rod, or optional levelling plate with levelling feet and integrated bubble <br />level. The figure below includes an Instantel Standard Transducer (a) and a Standard Transducer <br />with levelling plate (b). <br />• <br />B1astlMate III Operator Manual rJ-5 <br />