Instantel 716A0401, Operator'S Manual

Page: 63 / 86

Reference
MiniMate Plus Operator Manual
5–13
b. Zero Crossing Frequency (ZC Freq)
The Zero Crossing Frequency calculation for sound pressure is the same calculation used for
ground vibrations. Please see above for a complete discussion.
Note: The Zero Crossing Frequency calculation is performed for Linear “L” microphones only.
This calculation does not appear on the MiniMate Plus display when using an “A”
Weight microphone.
5.6. Alternate Manual Waveform Calculations
The following sections discuss manual waveform analysis techniques. These have been included
for reference purposes only. They do not represent the calculation techniques employed by the
BlastMate III.
Graphical methods for calculating area and slope depend on the shape of the waveform being
analyzed. A complete discussion of the procedures is beyond the scope of this manual. Two useful
reference texts are G. A. BOLLIGER,
BLAST VIBRATION ANALYSIS , Southern Illinois
University Press and CHARLES H. DOWDING, BLAST VIBRATION MONITORING AND
CONTROL , Prentice–Hall Inc.
In each of the subsequent examples some formulae appear with no attempt at derivation. The
following definitions apply:
A = amplitude in inches/second measured from the zero line
A
m
= amplitude measured in millimeters/second
T = period in seconds
Y = absolute change in amplitude over time measured in inches/second
Y
m
= absolute change in amplitude over time measured in millimeters/second
5.6.1. Sinusoidal Waveforms
The motion is essentially sinusoidal with gradual amplitude and frequency changes.
Figure 5.15 Manual Waveform Calculations on Sinusoidal Waveforms.
a. Calculating Displacement:
Maximum Displacement (in.) =
T
2
A
π
×