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c. Transducer Calibration Requirements <br />The geophone sensors inside Instantel's transducers must be calibrated annually by Instantel or an <br />authorized Instantel service facility. Contact your dealer for further information. <br />5.2.2 Microphone <br />The microphone measures air pressure. Instantel offers nvo types. Linear "L" (standard) and "A" <br />Weight (optional). Both come wi[h a three (oot (one meter) microphone mounting stand. <br />a. Measurement Scales <br />The Blasthlate III supports two sound pressure measurement scales: Linear "L" and "A" Weight. <br />(1) Linear"L" <br />Linear measurement is generally used to measure the effect of low frequency air pressure on <br />buildings. The linear scale records sound pressure without modification in the ? to 300 Hz range. <br />tvleasuremen[ units may be in absolu[e. Pascal, or relative d6 scales. <br />(2) "A" Weight <br />"A" W'eieht measures noise levels people may consider an annoyance. The incoming signal is <br />filtered over a 20 Hz to 20,000 Hz range reFlec[ing the hearing range of the human ear. The signal <br />is then converted to root mean square (RMS). Uni[s are measured using the decibel scale, dB(A). <br />b. Microphone Calibration Requirements <br />Instantel's microphone must be calibrated annually by Instantel or an authorized Instantel service <br />facility. Contact your dealer for further information. <br />5.3 Sensorcheck® <br />Sensorcheck performs a two stage test on the Blasthlate II I and its sensors. In the first stage, the <br />program displays the Blasthlate III serial number, software version, the total amoun[ o(memory <br />installed in the Blasthlate III, the total amount of memory available [o store events, and the <br />number of events presently stored in memory. The second stage tests each geophone within <br />Instantel's transducer and the microphone operation. The program also tests the operation of the <br />BlastMate III i[self and the sensor connecting cables. Pass or fail results appear on the display. See <br />the Basic Reference chapter of this manual to choose when Sensorcheck operates automatically. <br />5.3.1 Checking the Transducer's Geophones <br />Sensorcheck measures a geophone's natural frequency and damping indica[ed by an Overswing <br />Ratio (OR). Sensorcheck sends an elec[ric pulse to the geophones and measures the response. If <br />the geophone's response falls within a specified calibration range, the geophone is in calibration <br />and moni[oring operations can continue. If the geophone's response does not fall within a <br />specified calibration range, the eeophone is no[ calibrated. You cannot record events until you fig <br />or replace the geophones. See the troubleshooting sec[ion of this manual For [he appropria[e <br />procedures to follow. <br />a. Natural Frequency <br />• <br />Waveform measurements check the natural period (t) of a geophone's sensor coil assembly. <br />Referring [o the figure below, the dis[ance from P, to P: represen[s 0.125 seconds. Since <br />Frequency is the reciprocal of the period, F=1/[. the frequency is approximately 8 Hz. A calibrated <br />sensor has a natural frequency between 6.5 and 9.5 Henz. Calculations for all geophones appears <br />with each recorded event. <br />BlastMate III Opera[or Manual 5-5 <br />