Copyright © 2012 Test Products International, Inc. 9070 Vibration Analysis
PAGE 6
Bearing Noise (BDU)
Below the displayed ISO value and to the left is the value of bearing
noise (high frequency vibration) in Bearing Damage Units (BDU),
where 100 BDU corresponds to 1g RMS vibration measured above
1kHz. This is a measure of the wear state of the bearings in the equip-
ment being monitored. The higher the number, the more worn the bear-
ing.
It is generally held that 1g of high frequency vibration (100 BDU)
corresponds to a high level of bearing noise and so can be considered
indicative of a damaged bearing. In other words, it may be helpful to
think of the Bearing Noise figure as being very roughly equivalent to
“percentage” of bearing wear.
By default, the bearing noise is displayed on a Red background if it is
above 100 BDU, an Amber background between 50 and 100 BDU
and a Green background below 50 BDU. The BDU alarm levels can be
changed using the Advanced Settings Menu (see section 2.3.3.1).
Total acceleration (g)
This is the RMS (average) value of the total vibration in the ISO
frequency range (10Hz to 1kHz). This reading is shown in units of g
or Earth’s gravitational constant, (where 1g = 9.81 m/s
2
).
2.2.2 Vibration Analysis
Pressing the square button brings
up a display similar to that shown
opposite, which shows the readings
of vibration velocity (mm/s or inch/s)
broken down into each of 3 bands.
The display shows the vibration velocity in frequency ranges that are all
based on multiples of the specified Run Speed of the machine, and as
displayed beneath the 3 bar graphs.
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