Triggering
3-40 CSA8000B & TDS8000B User Manual
Gated Triggering. For instruments equipped with Option GT, the system allows
triggering to be enabled and disabled (gated) based on a TTL signal at a rear
panel input. See To Use Gated Trigger on page 3--50.
The key points that follow describe operating considerations for setting up to
trigger on your waveforms.
Triggering Process. When a trigger event occurs, the instrument acquires a
sample in the process of building a waveform record. The trigger event
establishes the time-zero point in the waveform record and all samples are
measured with respect to that event.
The trigger event starts waveform acquisition. A trigger event occurs when the
trigger source (the signal that the trigger circuit monitors) passes through a
specified voltage level in a specified direction (the trigger slope). When a trigger
event occurs, the instrument acquires one sample of the input signal. When the
next trigger event occurs, the instrument acquires the next sample. This process
continues until the entire record is filled with acquired samples. Without a
trigger, the instrument does not acquire any samples. See Figure 3--9 on
page 3--29. This behavior differs from that of real time acquisition systems,
which can acquire a complete waveform record from a single trigger event.
Triggering is Global. The instrument uses the trigger event to acquire across all
active channels. This same trigger is also common across all time bases currently
active (one or more of Main, Mag1 and Mag2).
Edge-Trigger Type. This instrument supports edge triggering only, in which edge
triggers gate a series of acquisitions.
The slope control determines whether the instrument recognizes the trigger point
on the rising or the falling edge of a signal. See Figure 3--11. You can set the
trigger slope from the toolbar at the top of the display or in the Trigger Setup
dialog box.
The level control determines where on that edge the trigger point occurs. The
instrument lets you set the trigger level from the front panel with the Trigger
LEVEL knob.
Keys to Using