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5-19
What’s more, by enabling the Auto Save option, each new event to be detected is automatically saved to Memory 1
to Memory 4. By setting the Auto Save option, you can automatically fill up all four memories with the four most
recent unusual events.
Best of all, Glitch Snare operation is completely automatic. Trigger thresholds are calculated automatically based on
recent signal history
.
The measurement used as a basis for Glitch Snare
operation is Period
by default. Certain
COMPONENT TESTS use other measurements, and some tests disable Glitch Snare when it is inappropriate.
Glitch Snare is most useful with continuous AC or digital signals where the information is embedded in the signalís
frequency, pulse width or duty factor.
To enable Glitch Snare operation, press the
G
litch Snare function key in the Scope mode of the COMPON
E
NT
TESTS. If Glitch Snare is available for the current test, the instrument will display the Glitch Snare display in a line
along with a conventional scope display in a solid line for comparison. Vertical and
horizontal settings
f
or both
displays are matched.
For example,
5.8 TIPS FOR NOISE MANAGEMENT
The instrument is very sensitive to spikes and other noise pulses which may be present on automotive signals. While
this capability can be valuable when tracking down glitch related problems, it can also obscure the signal you really
want to see in DC circuits such as power distribution.
If noise is obscuring the signals you want to see, try the following tips:
Using the Internal Battery Power
In general, noise pickup is minimized when you use this instrument on its internal battery power. Using the standard
Shielded Test Leads supplied will help in noise rejection
5-18
COMPONENT TESTS
ACTUATORS
INJECTOR PFI/MFI
MENU ( )
•
Press to remove the message and the following Function Key Labels will be displayed on the screen.
• Use and to display the previous or the next screens in memory. These keys are effective only if more than
one screen has been saved in memory. The number indicates the recalled memory location.
Press to select the displayed screen. The instrument activates the settings that are valid for the recalled screen
to test the input signal.
5.7 GLITCH SNARE OPERATION
Glitch Snare is a powerful combination of capabilities which enables you to reliable capture and display Actual Signal
Waveforms associated with elusive and unusual signals.
Gli
t
ch Snare combines real-time measurements with
specially designed scope trigger facilities, monitoring
measurement results on an event by event basis and triggering on any result which deviates above or below the
norm by more than a present limit. The input signal is captured at the moment when a trigger event occurs.
Imagine the frequency graph from
an AB
S
sensor with an occasional dropout
due
t
o an
intermittent
shor
t
in the
cable. As the wheel spins, the frequency output is stable until it briefly drops out due to the short. A graph of the
frequency shows a stable value until the short occurs.
At that instant
the graph show a sharp spike downward
indicating that the frequency went to zero. Now imagine being able to set “trigger thresholds” above and below the
stable frequency value shown on the graph so that when the downward spike on the graph occurs, a trigger event is
generated. This is the essence of Glitch Snare operation.
When ordinary scopes try to detect dropouts and other sudden changes in continuous AC signals, the majority of the
signal is ignored because these instruments only display new waveforms at the rate of a few per second. Therefore,
it is
not easy for them to capture and display the occasional glitch or dropout. And if an in
t
eres
t
ing event does
happen to be captured, it is soon overwritten with the next normal event, making detailed examination impossible.
The Glitch Snare operation triggers only on abnormal signal conditions, which virtually guarantees you’ll catch the
first event to come along. The captured signal waveform remains displayed in the Glitch Snare display for you to
examine until it is overwritten by the next unusual event.
The screen from memory 4 is displayed.
OK
MEMORY RECALL
SEARCH WFM
BACK RUN
4 ERASE
ACTUATOR INJECTOR PFI/MFI
REF WFM
GLITCH KEYS
BACK
OFF SNARE MOVE A
ACTUATOR INJECTOR PFI/MFI
AUTO SAVE
KEYS
BACK
ON MOVE A