Gen II User Manual
14-8 – Vibration Spectrum Survey Chapter 14 Revision 4.10, Apr 2020
To define Speed inputs, do the following:
14.1.1.3.1. In the “Measure” column, use the [] or [] key to select from “Pulse S”, “Pulse D” or
“None” indicating the tachometer input type for the tachometer input channel indicated.
NONE is selected when the corresponding tach channel is not being used. Pulse is used
when there is a pulse input such as a Phototach, Lasetach or magnetic pickup. This pulse
input may be, but is not necessarily a once-per-rev pulse. The preference is actually a
multi-pulse per revolution input. The D or S in the selection depicts either single-ended
(S) or differential (D) as required.
14.1.1.3.2. The “DESC” column is the descriptive name for the tachometer input such as “N1”,
“N2”, or “Fan”. Enter up to five alphanumeric characters in this field. The description
should be one that all users of this setup are familiar with and easily understand.
14.1.1.3.3. The “100% Spd” column is used to enter the rpm at 100% of component speed. Use the
keypad to enter the value in the “100% Spd” field. The example above shows “4800” and
“10000” for “N1” and “N2” respectively. This will allow the analyzer to also display the
component speed in percent during data acquisition. Therefore, when used on an engine
spool, N1 or N2 for example, the analyzer’s indication will match the cockpit indicator.
14.1.1.3.4. The “FACTOR” column can be used to enter a multiplier for converting Hertz to actual
component speed in RPM. If using a Pulse input, the RPM is equal to Hertz x Factor. The
analyzer assumes the input to be relative to Hz (cycles per second) so that an input of one
pulse per revolution (one-per-rev) would require a FACTOR of 60 (1 per-rev X 60 Hz
assumed) to equal Revolutions Per Minute (RPM). Enter the factor using the keypad. The
example above shows a factor of “60” for the “N1” to represent the usage of a
“LaseTach”. When sampling multiple pulses per revolution, you must know the tach
pulse frequency (Hz) of the tach source at 100%. The component speed (RPM) at 100%
is then divided by the tach pulse frequency to obtain the factor. In the example above, the
“N2” speed at 100% is 10,000 RPM and the tach pulse frequency is 4000 Hz. This will
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