User manual

WaveSurfer 3000/3000z Oscilloscopes Operator's Manual

Trigger

Triggers define the event around which digitized information is displayed on the grid.

Different Trigger Types are used to select different events in the trigger source waveforms: edge voltages,

pulse widths, high/low states, etc. These may be a single channel event or a complex pattern of events

across several channels. On instruments with Mixed Signal capabilities, many triggers can be set on either

analog channels, including the External Trigger input, or digital lines.

In addition to the type, the Trigger Mode determines how the instrument behaves as it encounters trigger

events: take a single acquisition and stop, holding on to the display of the last acquisition, or continuously

take and display acquisitions.

In both cases, when the previous acquisition has completed processing, the oscilloscope is again ready to

acquire and the READY indicator is lit. If, while READY, the trigger circuit detects a signal that matches the

trigger conditions, the oscilloscope triggers on the next matching event, and the TRIG'D indicator is lit.

Unless modified by a pre- or post-trigger Delay, the trigger event appears at time 0 at the horizontal center

of the grid, and a period of time equal to five divisions of the timebase is shown to the left and right of it.

Delay shifts the acquisition "window" on screen, displaying a different portion of the waveform.

An additional condition of Holdoff by time or events is available for Edge and Pattern triggers, including

those that appear within MultiStage triggers. Holdoff arms the trigger on the first matching event, inserts

the holdoff count, then triggers on a subsequent event. Often, especially with repetitive signals, the initial

arming event appears to the left of the trigger in "negative" acquisition time.

Trigger Modes

The Trigger Mode determines how often the instrument acquires. It is equivalent to how analog

oscilloscopes "sweep," or refresh, the display. Trigger Mode can be set from the Trigger menu or from the

front panel Trigger control group.

In Single mode, when you choose Trigger >Single or press the front panel Single button, the oscilloscope

readies, arms, and triggers provided all trigger conditions (including Holdoff) are met. It then stops and

continues to display the last acquisition until a new one is taken. The oscilloscope remains armed unless

manually stopped or triggered, and if a valid trigger does not occur, invoking Single a second time will force

a trigger and display the acquisition.

In Normal mode, operation is the same as in Single, except that the trigger automatically re-arms after the

previous acquisition is complete, and data is continuously refreshed on the touch screen.

Auto operates the same as Normal mode, except that a trigger is forced if the trigger event has not

occurred within a preset timeout period.

Stop ceases acquisition processing until you select one of the other three modes. The arming and Holdoff

counters are cleared, even if there has not yet been a trigger since the previous acquisition.