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A1: Meas. setup parameters in the 'Overall values' & 'Advanced' tab
Measurement quantity: Fixed; selection is carried out via the
measurement icon. Exception: The measurement quantity can be
changed for the 'Orbit', 'Phase' and 'Coastdown' measurement
tasks.
Sample frequency (Timewave Recorder): The sample frequency
for the time signal defines the maximum upper frequency and
influences the maximum measurement time.
Measurement time: Duration of an individual measurement; this
depends on the lower frequency.
Lower/Upper Frequency: Frequency range of the vibration
measurement. The DC component of the signal can be recorded
for the 'Vibration displacement' and 'User-defined' measurement
tasks (lower frequency = DC, see p. 5-30).
Average type / No. of measurements:
Without averaging: Each single measurement is displayed.
Linear averaging: Single measurements are added and divided
by the number of averages.
Exponential averaging: The measurements are averaged
exponentially. The final individual measurements are more
heavily weighted.
Peak hold: Highest measurement value is displayed.
Overlap: Percentage by which consecutive measurements overlap;
If the overlap is 0%, the total measurement time is: number
of averages x measurement time; the higher the overlap, the
shorter the total measurement time. For the runup / coastdown
curve, the number of usable measurements can be increased by
selecting a higher overlap.
Time syhnchronous averaging (Phase, Orbit): In this type of
averaging, the time signals of each individual rotation are
averaged to reduce non-synchronous components in the signal.
The number of time synchronous averages is either RPM-
dependent (Auto), user-defined or unrestricted:
'Auto': Number of averages is a function of the rotational speed*.
'Manual': Number of averages can be entered (max. 254).
'Unrestricted' (only in meas. setup for balancing): Each individual
measurement is averaged with the preceding individual
measurement. The longer the measurement takes, the more
stabile the final result. This averaging type is used for balancing
runs. The measurement must be stopped using the 'Enter' key.
During a phase measurement VIBXPERT calculates a phase vector
(amplitude and angle) from the time synchronous averaged
signal. This procedure is repeated several times in order to
increase the stability of the phase vector. The parameters for the
phase averaging correspond to the settings under "Average type /
Number of measurements' (see above).
Options
Acceleration, low-speed
* For example, time synchronous
number of averages = 3, if speed>120
rpm.
3-21
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