CEMB USA N300 - Manual (Page 28)

5 - 4 Vibrometer function
that even the high-frequency zone, where bearing-related problems usually occur,
can be included in the spectrum.
Note:
Other things being equal, the selection of a low maximum frequency (less than
1000 Hz) considerably lengthens the amount of time required for acquisition and
measurement.
2. No. of averages
Shown next to the N symbol, it indicates the number of spectrums that must be calculated
and averaged to increase the stability of the measurement. All values between 1 and 16 are
acceptable, but 4 averages are more than enough for normal vibration measurements on
rotating machines.
Settings for synchronous measurements only
1. Synchronous filter width:
This parameter, identified for historical reasons as the synchronous filter width, is displayed
next to the symbol and is measured as a percentage. It indicates the resolution in
frequency of the synchronous analysis, or rather the instrument’s ability to separate
contributions from the various frequencies.
Values from 1% to 100% are available.
For example, a value of 5% indicates that the contribution of all of the frequencies of the
1xRPM±5% band (which cannot be distinguished from each other) is included in the
calculation of the synchronous value.
Smaller values (or rather, narrower filters) produce more accurate measurements, but
require considerably longer acquisition times. For example, with a 1% filter and particularly
slow rotating bodies (60 RPM) you must wait for a few minutes before completing a
measurement.
To set this parameter you need to find the right balance between accuracy and time.
After setting the desired values, press to confirm them; or press the
key to quit the settings without changing the existing ones.