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SVANTEK 977W User Manual
12.2.1. Setting the measurement range for FFT - Range
For the
FFT
function the user can select the
input ranges specified in Appendix C,
named as
Low
and
High
.
The selection of the input range is doing in
the
Range
window of the
Measurement
list.
Depending on the settings of the
Scale
parameter (
path: <Menu> / Display /
Display Scale
) the range for vibration signal
can be presented in absolute or logarithmic
units (dB).
►
Note: The calibration factor is always added to the range limits.
For example, if calibration factor is equal to 0.5 dB, the range will
be changed automatically (lower and upper limits will be increased
by 0.5).
12.2.2. Setting the parameters of FFT analysis - FFT
The
FFT
position, which appears in
FFT
analysis, opens the window in which the
user can select the parameters of the FFT
analysis: averaging type (
Averaging
), pre-
weighting filter (
Filter
), frequency band
(
Band
), weighting window (
Window
) and
the number of lines (
Lines
) for the FFT
analysis.
<ENT>
In the
Band
position the user can select the band in which the
FFT
analysis should be performed. The user can
select:
20 kHz
,
10 kHz
,
5 kHz
,
2.5 kHz
,
1.25 kHz
,
625 Hz
,
312 Hz
,
156 Hz
and
78 Hz
.
The following pre-weighting filters are available for the
FFT
analysis of sound:
A
- type 1 according to the IEC 651 and IEC 61672-1 standards,
C
- type 1 according to the IEC 651 and IEC 61672-1 standards,
B
- type 1 according to the IEC 651 standard,
Z
- type 1 according to the IEC 61672-1 standard
HP
- type 1 according to the IEC 61672-1 standard
Only one
HP
weighting filter is available for the
FFT
analysis of vibration.
The characteristics of the filters are given in Appendix D.
In the
Window
position the user can select the weighting window for the
FFT
analysis of the signal. The user
can select
Hanning
,
Rectangle
,
Flat Top
and
Kaiser-Bessel
weighting windows.
In the
Lines
position the user can select the number of lines for the
FFT
analysis of the signal. The user can
select
1600
,
800
and
400
lines.
