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Chapter 5 . . <br />1 <br />L J <br />i\ote: The Zero Crossing Frequency calculation is performed for Lineaz microphones only. This <br />calculation does not appeaz on the BlastMate III display or on Event Summary Reporu <br />when using an "A" Weight microphone. <br />5.6. Alternate Manual Waveform Calculations <br />The following sections discuss manual waveform analysis techniques. These have been included <br />for reference purposes only. They do not represent the calculation techniques employed by the <br />BlastMate III. <br />Graphical methods Cor calculating area and slope depend on the shape of the waveform being <br />analyzed. A comple[e discussion of the procedures is beyond the scope of this manual. Two useful <br />reference [exts are G. A. BOLLIGER, BLAST VIBRATIONANALYSIS, Southern Blinois <br />University Press and CHARLES H. DOWDIIv'G, BLAST VIBRATION MONITORING AND <br />CONTROL, Prentice-Hall Inc. . <br />In each of the subsequent examples some formulae appear with no attempt at derivation. The <br />following definitions apply: <br />A = amplitude in inches/second measured from the zero line <br />Am = amplitude measured inmillimeters/second <br />T = period in seconds <br />Y = absolute change in amplitude over time measured in inches second <br />Ym = absolute change in amplitude over time measured in millimeterslsecond <br />• 5.6.1. Sinusoidal Waveforms . <br />The motion is essentially sinusoidal with gradual amplitude and frequency changes. <br />a. Calculating Displacement: <br /> T <br /> xA <br />Maximum Displacement (in.) = ZR <br /> T <br /> xAm <br />Maximum Displacement (mm) = 27[ <br />b. Calculating Acceleration: <br />- <br />Maximum Acceleration (inJsr) - <br />T X A <br /> <br />12 BlastMate III Operator Manual <br />