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22
The stream of shock pulses from a rotating bearing is con-
tinuous. They vary in strength, depending on the relative
positions of rolling elements and raceways.
The
headphone
is a means to verify and trace shock pulse
sources. The headphones allow you to listen to the shock
pulse pattern. In the headphone, the noise carpet is repre-
sented by a continuous tone. The dBc level is approximately
where you can start to distinguish between an even sound
and individual pulses. Typical for bearing signals is a random
sequence of strong pulses with no discernable rhythm, best
heard a few dB below the dBm level.
A spot of surface damage causing a strong shock pulse will
only register, if a roller hits it during the measuring interval.
Especially at low rotational speeds, the instrument can miss
the strongest pulse, simply because it does not occur during
the measuring interval.
To listen to the shock pulse pattern after taking an SPM
reading, connect your headphones to the output connector
(7). From the
Main
display, press the UP arrow key to enter
Bearing
mode. Use the LEFT/RIGHT arrow keys to highlight
the
Listening
icon, then press the UP arrow key to enter
listening mode, where the dBm value of the latest reading
is displayed. Use the UP/DOWN arrow keys to adjust the
amplitude level at which you wish to listen; anything below
this value will be filtered out.
To adjust the headphone volume use the RIGHT arrow key.
NOTE! Setting the volume to the maximum level may harm
your hearing.
To return to the
Bearing
display, press the LEFT arrow
key.
Headphones
dBn
Listening to the shock pulse pattern
Adjust
amplitude
level
Headphone volume
Adjustment of
amplitude level
Listening
Adjust
volume
Back
Bearing measurement