Table of Contents
Advertisement
)
)
Genera.I Information
Order
Order refers to how many times an event occurs
during one revolution of a rotating component.
95600
For example, a tire with one high spot would create a
disturbance once for every revolution of the tire.
This is called first-order vibration.
J
95601
An oval-shaped tire with two high spots would create a
disturbance twice for every revolution. This is called
second-.order vibration. Three high spots would
be third-order, and so forth. Two first-order vibrations
may add or subtra.ct from the overall amplitude of
the disturbance, but that is aH. Two first-order
vibrations do not equal a second-order vibration. Due
to centrifugal force, an unbalanced component will
always create at least a first-order vibration.
Vibration Diagnosis and Correction
0-81
Reed Tachometer
<JD
RESONANT REED
20
30
40
50
60
70
80
<ID
386790
The reed tachometer consists of two rows of reeds
arranged side-by-side. Each reed vibrates when
excited by a specific frequency. The reeds are tuned
to vibrate at increasing frequencies from left to
right This allows for a visual display of the frequency
range from 10-80 Hz.
Due to increasing costs, limited availability and limited
diagnostic capability, the reed tachometer is no
longer recommended as the primary tool in diagnosing
vibration.
Electronic Vibration Analyzer (EVA)
The J 38792 Electronic Vibration Analyzer (EVA), with
the J 38792-60 Electronic Vibration Analyzer
Cartridge, is specifically designed to diagnose
vibrations. This hand-held device is similar to a scan
tool. A standard 12-volt power feed supplies the power.
The vibration sensor, or the accelerometer, is at the
end of a 6 mm (20 ft) cord. The vibration sensor
can be mounted virtually anywhere on the. vehicle
where a vibration is felt.
EVA Basic Hookup
1. Verify that the software cartridge is correctly
inserted at the bottom of the unit. (The cartridge
usually remains there at all times.)
2. Connect the vibration sensor cord into either
Input A or B.
3. Line up the sensor connector so that the release
button is at the bottom.
4. Push the sensor connector into the input until the
connector clicks and locks into place.
5. Plug the power cord into a 12-volt power feed in
order to turn the EVA on. (The EVA is not
equipped with an ON-OFF switch.)
To disconnect the sensor connector, press the release
button and gently pull the connector straight out
Advertisement
Chapters
Table of Contents
