GxT Ferret 92 Color Labscope - Manual (Page 7)

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Trigger Modes
Understanding and applying a trigger is the most powerful function of any labscope. The VisionLink supports
many different and unique triggers. Make sure you take the time to apply each one and understand how each one
can help you locate a problem. Only one trigger can be used at any time. Any trigger mode can be applied to any
channel.
None
When this trigger is used, the scope is actually triggering itself continuously. Sometimes it is best to use this trigger
to catch a glimpse of the waveform to help you select the most appropriate trigger. At timebases of greater than
1 second, the scope will update the screen using a rolling mode from left to right. This is the best trigger to use
when checking sensors like the TPS sensor.
Up Slope
This trigger is displayed on the screen as ↑Trig. You can use the trigger arrows to change the voltage level used
to trigger. When this trigger is selected, the scope uses the trigger voltage level and watches for the waveform to
move up from that voltage. When it does, the pattern is drawn on the screen. The actual trigger point is marked
by a small white diamond on the trace itself.
Down Slope
This trigger is displayed on the screen as ↓Trig. You can use the trigger arrows to change the voltage level used
to trigger. When this trigger is selected, the scope uses the trigger voltage level and watches for the waveform to
move down from that voltage. When it does, the pattern is drawn on the screen. The actual trigger point is marked
by a small white diamond on the trace itself.
Cyl #1
This trigger used the Red Spark Pickup as an external trigger. While the trigger symbol suggests that the red pickup
be connected to Cylinder #1, it can be connected to any cylinder you wish. The time base is adjustable by the
user. Whatever channel you have this trigger attached to will activate the peak detect function. The peak detect is
good for displaying the ignition pattern. The trigger level arrows can be used to change the level of the peak detect
software. If you keep the peak detect level at or close to ground you will get a good looking ignition pattern. If
you set the peak detect above the pattern being displayed, it will have the effect of squelching the ignition pattern
except where a peak is detected above the set peak detect level.
RPM
This trigger is used when you want one engine cycle displayed on the screen, no matter what the RPM. When
displaying ignition waveforms on a 6 cylinder (for example), when using the RPM trigger you will see 6 cylinders and
part of cylinder 1 again at the end of the pattern. If you rev the engine up and down, the patter stays stable and
only the proper number of cylinders are displayed. When using this mode, the RPM is calculated and displayed in
place of the timebase. Use the NEXT key to toggle between 2 cycle and 4 cycle. The trigger level arrows can be
used to change the level of the peak detect software. If you keep the peak detect level at or close to ground you
will get a good looking ignition pattern. If you set the peak detect above the pattern being displayed, it will have
the effect of squelching the ignition pattern expect where a peak is detected above the set peak detect level.