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Reference <br />• <br />5.3.7. Checking the Transducer's Geophones <br />Sensorcheck meazures a geophone's natural frequency and damping indicated by an Overswing <br />Ratio (OR). Sensorcheck sends an electric pulse to the geophones and measures the response. If <br />the geophones response falls within a specified calibration range, the geophone is in calibration <br />and monitoring operations can continue. If the geophone's response does not fall within a specified <br />calibration range, the geophone is not calibrated. You cannot record events until you Fx or replace <br />the geophones. See the troubleshoo[ing section oC this manual for the appropriate procedures to <br />follow. <br />a. Natural Frequency <br />Waveform measurements check the natural period (t) of a geophone's sensor coil assembly. <br />Referring to the figure below, the distance from Pt [o Pz represents O.I25 seconds. Since <br />Frequency is [he reciprocal of the period, F=1/t, the frequency is approximately 8 Hz. A calibrated <br />sensor has a natural frcquency between 6.5 and 9.5 Herz. Calculations for all geophones appcaz <br />with each recorded event. <br />• <br />frequency. <br />b. Damping - Overswing Ratio (OR) <br />The overswing ratio (OR) meazures damping and is calculated by computing the ratio of the <br />magnitude of adjacent waveform peaks according to the following formula: <br />A <br />OR= At <br />Acceptable overawing ratios range from 2.8 to 4.8. The figure below displays a graph of a <br />geophone coil's "free fall" response. At and A= are used for overawing calculations. <br />• <br />Ratio. <br />BlaztMate III Operator Manual <br />5-7 <br />