Using Sequence Mode, thousands of trigger events can be stored as segments into the oscilloscope's acquisition memory (the exact number depends on oscilloscope model and memory options). This is ideal when capturing many fast pulses in quick succession with minimum dead time or when capturing few events separated by long time periods. The instrument can capture complicated sequences of events over large time intervals in fine detail, while ignoring the uninteresting periods between the events. You can also make time measurements between events on selected segments using the full precision of the acquisition timebase.
Sequence mode offers a number of unique capabilities:
You can acquire up to four channels simultaneously.
You can minimize dead time between trigger events for consecutive segments.
You can view time stamps for acquisitions.
You can zoom segments or used them as input to math functions.
You can combine sequence mode with an advanced trigger to isolate a rare event, capture all instances over hours or days, and view/analyze each afterwards.
LeCroy’s ‘all instance’ measurement parameters function across all segments.
You can use Sequence mode in remote operation to take full advantage of the instrument's high data-transfer capability.
Displays shown in the tutorial are based on the following initial setup on a WaveRunner 6 Zi scope:
- Connect a coaxial cable from channel 1 to the Aux connector on the front panel.
- Recall the default setup: File pull down > Recall Setup> Recall Default.
- Turn off channel 2.
- Set the input coupling on Channel 1 to be 50 Ohms: Touch or click the channel 1 annotation box>touch or click on the coupling field >select DC 50 Ω.
- Set up the Aux output to be the Fast Edge signal. Utilities pull down > Utilities Setup >Aux Output Tab>touch or click on Fast Edge. The Fast Edge signal is a 5 MHz, 450 mVp-p, square wave.
- Auto Setup the scope: Press Scope Setup then select Auto Setup from the fly-out menu.
- Using the C1 dialog box, set the channel 1 vertical scale to 100 mV/division and the vertical offset so that the bottom of the trace is one division above the bottom of the display grid.
- Set the trigger level to 170 mv (three divisions down from the top of the display).
- This completes the initial setup. The scope display should be similar to Figure 1.
Open the Timebase dialog box by either touching or clicking the Timebase annotation box or using the Timebase pull-down menu and selecting Horizontal Setup. Change the Time /Division field to10 ns/division. Press the Sequence button this will turn on the Sequence acquisition mode.
Click or touch the Sequence Tab on the Timebase dialog box to display the sequence mode controls as shown in Figure 2.
Double click or touch the Acquisition Settings field twice. This will bring up the ‘Number of Segments’ pop up box. Press the ‘Set to Max’ button and observe the maximum number of segments for your scope (this is scope and memory dependent). Press the ‘Set to Min’ button. The minimum number of segments is 2. Press the ‘Set to Default’ button to restore the number of segments to 10. Press ‘Cancel’ to close the pop up. It is also possible to set the number of segments by touching or clicking on the Acquisition Settings field and turning the WavePilot SuperKnob.
In sequence mode the scope will continue to acquire data until all the segments are filled or until the user presses the “Stop’ button on the front panel. There is also a ‘Sequence Timeout’ setting on the sequence tab (In Figure 3) to stop the acquisition after a preset time delay without a trigger event.
Press the ‘Show Sequence Trigger Times’ button on the Timebase, Sequence tab. This will display a table listing the sequence mode trigger time, shown in Figure 4. The trigger time table has four columns.
These are Seg (for segment number), Time, (time) since Segment 1, and (time) between Segments. In Figure 4 the table shows ten segments, if there were more an index selection will appear to allow you to select the number of the first segment displayed in the table.
Each segment has an absolute time stamp which is derived from the scopes real time clock with 1 sec displayed resolution. The relative time stamps read the time since segment 1 and the time between segments. These display time down to nanosecond resolution. Internally, the relative time stamps have picosecond resolution which can be accessed via remote commands.
You can view each segment individually by using the zoom function. Press the ‘Zoom’ button on the front panel. The ‘Horizontal Delay’ control can be used to scroll through each segment. The Zoom dialog box (shown in Figure 5) allows users to select the first segment and the number of segments displayed in each zoom trace. Multiple zoom traces can be used to select and compare different segments.
An alternative method to view individual segments is to use the Math Segment function. This behaves the same way as the zoom trace with the ability to set the first and number of segments as shown in Figure 6.
Turn off the zoom and math traces.
Press the ‘Stop’ button in the trigger group on the scope’s front panel to stop the acquisition.
Use the ‘Utilities’ pull down menu to access the ‘Utilities Setup’ dialog box.
Select the ‘Aux Out’ tab from the utilities setup.
Select the ‘Off’ button in the ‘Use Auxiliary Output for’ group.
Press the ‘Single’ button in the trigger group on the scope’s front panel to stop the acquisition.
Return to the ‘Aux Output’ tab on the Utilities setup. Press the Fast Edge button. The scope should trigger once acquiring ten segments and then stop. The vertical offset of each segment should be slightly different as shown in Figure 7. We have captured the turn-on transient response of the FastEdge signal over the first 10 edges. Note that in single trigger mode the scope will fill each segment in the sequence mode.
Bring up the ‘Timebase’ dialog and select the ‘Sequence’ tab. Change the ‘Display Settings’ field from ‘Adjacent’ to Overlay. The screen should appear as shown in Figure 8.
We have changed the sequence mode display from Adjacent, where each segment appears side by side with all the other segments in the order they were acquired, to Overlay. In Overlay display mode all the segments are displayed on a common set of axes so they can be compared.
There are five sequence mode display formats. In addition to Adjacent and Overlay there are Waterfall, Perspective, and Mosaic. These are shown in figures 9-11.
Return the Display Mode to ‘Adjacent’ .
Use the ‘Measure’ pull down menu and select Measure setup. Setup parameter P1 to measure the mean value of channel C1, and P2 to measure the risetime of C1. Click the P1, P2, ‘Show Table’, and Statistics On’ check boxes as shown in Figure 12.
LeCroy’s ‘All Instance’ measurements can be applied to sequence mode acquisitions directly. In the example above you see how each of the measurements returned 10 measurements, one for each segment.
As a final example we will plot the trend of the mean value parameter. Click or touch the P1 tab in the measurement dialog box. Press the ‘Trend’ button in the ‘Actions for P1 Group’. A pop up menu will prompt for what math trace to place the result in. Select function trace F1. The math function trace F1 will appear. Touch or click the F1 trace annotation box. Touch or click on the Trend tab. Change the ‘Values to Trend’ setting from the default (1000) to 10. This will display a ten point trend of the mean value of each segment as shown in Figure 13.
This completes the tutorial.