GMC Chevrolet Camaro 1998 Service Manual page 109

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General Information
The freeze function can be used in order to freeze the
display at any point in the sequence during playback.
Individual frames can be viewed in a forward or
backward sequence using the up and down
arrow keys.
The display returns to the active screen when the
recording or playback of a snapshot is finished,
or when EXIT is pressed.
Averaging/Non-Averaging Modes
The EV A normally operates in an averaging mode that
averages multiple vibration samples over a period of
time. The averaging mode minimizes the effects
of sudden vibration that are not related to the problem
(such as form potholes or uneven road surfaces).
Most tests use the averaging mode.
The EVA is more sensitive to vibrations in the
non-averaging mode. The display is more
instantaneous and not averaged over a period of time.
The non-averaging mode is used when measuring
a vibration that exists for only a short period of time,
and during acceleration/deceleration tests.
Pressing the AVG button switches between the
averaging and non-averaging modes. The screen will
display AVG.
Strobe Balancing
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The EVA can strobe balance a rotating component. A
trigger wire is located on the top of the EV A, which
is used in conjunction with an inductive pick-up
light strobe. The EV A triggers the strobe light at the
same frequency as the vibration. The timing light clips
on to the trigger wire. The vibration sensor must be
attached to input A. Input B does not provide the
strobe function.
Pressing STROBE starts the strobe balancing function.
The EVA will ask a series of questions in order to
determine the correct filter range: full, low, or high.
Vibration Diagnosis and Correction 0-97
The low and high ranges prevent other vibrations from
interfering with the operation of the strobe light. Use
the full range as a last resort only. Press YES in order
to select a range. Press NO in order to go on to the
next range. The vibration/strobe frequency must
fall within the selected range.
The EVA will display the strobe frequency, amplitude,
and filter range. The EVA is now ready to begin
the strobe balance procedure.
EVA Calibration
The EVA features the following two built in calibration
procedures:
• Sensor Calibration
• Phase Shift Calibration
A replaced or added sensor must be calibrated in
order to function properly with the EVA unit. The phase
shift calibration is performed at the factory and
should not be repeated under normal use.
Sensor Calibration
1. Lay the sensor on a flat stationary surface with
the UP side facing upward.
2. Plug the sensor into either input A or B.
3. Plug the EVA into a 12-volt power supply.
4. After the display initializes, select the proper input.
5. Press the up arrow key.
6. Press the number 2 three times on the keypad.
The message BURNING will appear, followed by
a request to turn the sensor over.
7. Turn the sensor over.
8. Press any key in order to commence calibration:
• Calibration will take about 20 seconds.
• The display will return to the active mode
when calibration is complete.
Phase Shift Calibration
1. Plug the EVA into a 12-volt power supply.
2. Press the down arrow key on the EVA keypad.
3. Press the number 2 three times in order to begin
calibration:
• Do not press any key until the message ANY
KEY TO CONTINUE appears. Pressing a
key will cancel the calibration process.
• The display will flash numbers for 5-6 minutes.
(If the numbers flash for more than 1 O minutes,
the EVA is defective.)
• The message BURNING PHASE SHIFT
CONSTANTS will appear for one minute.
• The BURNING CENTER FREQUENCIES
LOW=39 HIGH=48 message will appear.
• The ANY KEY TO CONTINUE message should
appear.
4. Press any key in order to return to the
active mode.