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dataPAC User’s Guide
Chapter 4 - Off Route Analysis with the dataPAC
Trigger Type
Press <SELECT> while in the Trigger Type box to select from a list of trigger types.
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None indicates that the machine speed is not to be measured. This is only possible for
an FFT/Waterfall measurement.
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Positive Slope indicates that the machine speed is measured using the positive edge of
the trigger signal as the phase reference.
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Negative Slope indicates that the machine speed is measured using the negative edge of
the trigger signal as the phase reference.
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Leading Edge or Trailing Edge automatically selects the rising edge or the falling
edge. The selection depends upon the trigger pulse width and polarity. If the trigger
input in a narrow positive pulse, Leading Edge selects the rising edge for the trigger
event, and Trailing Edge selects the falling edge. If the trigger input is a narrow
negative pulse, then leading edge selects the falling edge, and trailing selects the rising
edge. See the illustrations below.
Trigger Level
If the Trigger Type is set to something other than None, press <SELECT> to toggle between
Auto and TTL. Auto sets the trigger level based on the trigger input signal. TTL sets the
trigger level to a value of 1.4 volts.
Tach/Gear Box (Bode/Nyquist only)
The Tach/Gear Box parameters are used to configure the dataPAC to measure information
for a buried shaft, where you cannot measure the shaft speed directly. Select this option to
enter the number of gear teeth associated with the input trigger source.
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Trigger Pulses/Revolution - Indicates how many trigger pulses occur for each
revolution of the reference shaft. If this parameter is set to a value other than 1, there
will be an initial phase angle ambiguity.
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Tooth Count - Indicates how many teeth are present on the external shaft and the
internal shaft. If these values are set to 1, then the external shaft trigger is used directly.
Otherwise, the external reference is converted to a new reference that matches the
speed of the internal shaft. In this case, the phase measurement is only relative.
leading edge
trailing edge
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