History Mode

The WaveRunner 6 Zi family of scopes includes a new feature called History mode. History mode lets you scroll back in time to isolate anomalies and other waveform events, measure them with parameters or cursors, and quickly find the source of the problem. History mode is always buffering waveforms, so no user action is required to save traces other than to invoke the viewer. The depth of the history buffer is model and memory option dependent. For models equipped with the –m memory option (64MS/channel), the buffer is 128 MS. The number of waveforms stored in the history buffer is dependent on the length of the acquisition, from 256k acquisitions for a 4 point waveform to two acquisitions for a 50Mpoint waveform. WaveRunner HRO models, due to the 12 bit resolution, have about one half the total number of acquisitions stored in the History buffer. In all instances, the Waveforms Available field on the History mode display will clearly indicate the number of archived acquisitions.

When History mode is enabled the user can view a table showing all the available acquisitions. Controls allow selection of any specific waveform and offer the facility to pan through all archived acquisitions automatically. Like all LeCroy Oscilloscope tables this one is hyperlinked and simply touching or clicking on an entry will bring up the associated acquisition on the display. Each acquisition is tagged with both an absolute time stamp based on the real time clock and a relative time stamp referenced to the last acquisition.

Displays shown in the tutorial are based on the following initial setup on a WaveRunner 6 Zi scope:

  1. Connect a coaxial cable from channel 1 to the Aux connector on the front panel.
  2. Recall the default setup: File pull down > Recall Setup> Recall Default.
  3. Turn off channel 2.
  4. 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.
  5. 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.
  6. Auto Setup the scope: Press Scope Setup then select Auto Setup from the fly-out menu.
  7. 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.
  8. Set the trigger level to 170 mv (three divisions down from the top of the display).
  9. This completes the initial setup. The scope display should be similar to Figure 1.

Figure 1:

The oscilloscope initial setup showing 10 cycles of the FastEdge signal

Turn on the History mode by pressing the History button in the WavePilot area on the front panel or by using the Timebase pulldown, Timebase>History. The display should appear as shown in Figure 2.

Figure 2:

The History mode dialog box showing the History acquisition table and scroll controls

Note that when the History mode is evoked the acquisition is stopped. The ‘View History’ checkbox can be used to turn History mode off and on. When it is unchecked the table will be cleared and the trigger mode will be restored to its state prior to evoking the History mode.

The Clear History button will clear the history table and acquisition memory buffer. Once the buffer is cleared it can only be updated by returning the oscilloscope trigger mode to Auto, Normal, or Single modes. This will turn off History mode.

The ‘Waveform History Navigation’ controls, shown in Figure 3, allow you to control the selection of the desired archived acquisition. The top row of buttons control automatic panning through the history entries. The lower set of buttons allows you to jump to the oldest record, the newest record, or to jump line by line through the table. The Index entry field allows for a numeric entry of the desired history entry. The manual scroll bar (duplicated to the right of the table in Figure 2) allows manual scrolling through the table entries. The table is hyperlinked and touching or clicking on any entry will cause the selected entry to be displayed. You can also use the SuperKnob to scroll through the table.

Figure 3:

The Waveform History Navigation Pane

The View Table check box controls whether the History table is displayed. The Relative Time check box selects whether the absolute time of the acquisition or the relative time from the last acquisition is displayed in the table.

Place the oscilloscope into the Single Trigger Mode by pressing the Signal button on the front panel. The scope will acquire a single waveform and stop.

Press the History button in the WavePilot area on the front panel. When the History dialog box appears press the ‘Clear History’ button.

Using the Utilities pull down menu, navigate to the Aux Output tab on the Utilities Setup dialog box (Utilities>Utilities setup>Aux Output tab). In the pane marked ‘Use Aux Output for’ press the off button.

Press the ‘Single’ button in the trigger area on the front panel. The Single indicator will be lit.

Press the ‘Fast Edge’ button on the Aux Output tab. The oscilloscope should acquire a single trace.

Repeat the last three steps ten times.

Turn on History mode again using the History button in the WavePilot area. There should be ten entries in the History table as shown in Figure 4.

Figure 4:

The History table after acquiring 10 waveforms

Use the WavePilot SuperKnob to scroll through each of the ten acquired waveforms. Try touching each entry in the History table; note that the selected waveform is displayed.

Use the scroll controls in the ‘Waveform History Navigation’ pane in the History dialog box to scroll up and down through the list. Use the Jump to Oldest and Jump to Newest buttons and observe their operation.

Change the time readout in the table from absolute time to relative time by checking the ‘Relative Times’ check box. The time stamps in the table should now show zero at the bottom with increasing negative time values as you go up the table as seen in Figure 5.

Figure 5:

The display of relative times in the History table

Note that it is possible to save any displayed acquisition from the History mode by using the Save Waveform selection in the File pull down menu as shown in Figure 6.

Figure 6:

Setup to save the selected History waveform

Likewise, you can apply measurements or math operations to any selected History acquisition. An Example of both operations is shown in Figure 7.

Figure 7:

An example of applying math (invert) and measurement (cycles) to a selected history waveform

Here are counting the number of complete cycles on waveform (5) and showing the Invert math function of that same trace. Try applying both measurement and math operations to one of your selected acquisitions.

This completes the tutorial.