Agilent Technologies 54621D, 24A, 42A, 54621A, 22A To select a trigger mode Normal, Auto, Auto Level

Triggering the Oscilloscope

To select a trigger mode: Normal, Auto, Auto Level

To select a trigger mode: Normal, Auto, Auto Level

1Press the Mode/Coupling key.

2Press the Mode softkey, then select Normal, Auto, or Auto Level mode.

•Normal mode displays a waveform when the trigger conditions are met, otherwise the oscilloscope does not trigger and the display is not updated.

•Auto mode is the same as Normal mode, except it forces the oscilloscope to trigger if the trigger conditions are not met.

•Auto Level mode (54620-series only) works only when edge triggering on analog channels or external trigger. The oscilloscope first tries to Normal trigger. If no trigger is found, it searches for a signal at least 10% of full scale on the trigger source and sets the trigger level to the 50% amplitude point. If there is still no signal present, the oscilloscope auto triggers. This mode is useful when moving a probe from point to point on a circuit board.

Auto Level and Auto modes

Use the auto trigger modes for signals other than low-repetitive-rate signals and for unknown signal levels. To display a dc signal, you must use one of these two auto trigger modes since there are no edges on which to trigger.

Auto Level mode (54620-series only) is the same as Auto mode with an automatic trigger level adjustment. The oscilloscope looks at the level on the signals, and if the trigger level is out-of-range with respect to the signal, the scope adjusts the trigger level back to the middle of the signal.

When you select Run, the oscilloscope operates by first filling the pre-trigger buffer. It starts searching for a trigger after the pre-trigger buffer is filled, and continues to flow data through this buffer while it searches for the trigger. While searching for the trigger, the oscilloscope overflows the pre-trigger buffer; the first data put into the buffer is the first pushed out (FIFO). When a trigger is found, the pre-trigger buffer will contain the events that occurred just before the trigger. If no trigger is found, the oscilloscope generates a trigger and displays the data as though a trigger had occurred.

When you select Single, the oscilloscope will fill pre-trigger buffer memory, and continue flowing data through the pre-trigger buffer until the auto trigger overrides the searching and forces a trigger. At the end of the trace, the scope will stop and display the results.

3-4