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Scope and Multimeter Operations

Capturing Data

127

9.11.2 Capturing Data (Capture Mode)

Whenever you open Lab Scope or the Graphing Multimeter, the device is in
Capture Mode. In Capture Mode, data is continuously being captured and stored in
buffer memory at the same time it is being displayed onscreen.

NOTE

Data is continuously stored in buffer memory with or without an active input
test signal or trigger.

To help you understand how to work with captured data, an important
concept to remember is that data is captured over a period of time. Therefore
there is a direct relationship between the length of time the data is captured
in, and the resultant level of detail you will have when reviewing it.

As every testing situation is different, the following is provided only as a guide when
capturing data to provide the best flexibility when reviewing the data to find events.

In most situations if you start by using a sweep setting that is best suited for viewing
the waveform “live”, or at a setting that provides the best detail to the naked eye,
this will allow you to either see the event you are looking for “live, or allow you to use
the zoom feature (in Review Mode) to zoom out (2, 8, 32X etc.) and then search
through the data buffer for events of interest.

It is important to remember that whatever sweep setting you use during data
capture is what the 1X zoom level will be when you switch to Review Mode.
Therefore, if you capture data using a sweep setting where the pattern displayed is
tightly compacted (can’t visually see detail), then when you try to use zoom you will
not be able to see any detail, as you will only be able to zoom out from the setting
where you originally captured the data (displaying an even greater level of
compacted data).

In other situations you may need to start at a faster sweep (shorter time) to capture
more detail “live”, then zoom out (in Review Mode) to get a wider view and then
zoom in at the points of interest where you need more detail. Using this strategy you
will capture less total time, but be able to see more detail.

For some situations, if the sweep setting you are using is not fast enough to capture
the event your looking for, turning Peak Detect on will increase the sample rate and
may allow you to see the event.

Using peak detect can also help in avoiding aliasing if the sweep time is too great
for the waveform being captured. Using peak detect is not appropriate for every

instance, but when using longer sweep settings, it can help increase the capture
time by allowing you to capture more than you could without it and still capture
dropouts and points of interest. See

Peak Detect Icon

on page 117

for more

information.

For additional information on setup and capturing data (input signals) see

General

Reference (Testing Strategies)

on page 145

NOTE

Glitches may cause drivability problems and may not turn on the MIL or set
DTCs. As a general guide when looking for a suspected signal glitch, always
try to verify the problem by duplicating the conditions while capturing data.
Utilize the GMM to monitor the signal over longer time periods and review the
histogram for possible faults.

The following control icons are active in the lower tool bar in Capture Mode..

For an alternate method of capturing data, see

Taking a Data Snapshot

page 131

9.11.3 Pausing Data

Data continuously stores in buffer memory until the

Pause

icon is selected.

Selecting the

Pause

icon, allows you to temporarily pause the data (input test

signal) to review it in detail. See