BK Precision 2560B Series, Руководство пользователя

Страница: 52 / 224

Note:
Trigger
For triggering, certain condition can be set according to the requirement and when a waveform in the waveform meets
this condition. Digital oscilloscope, display a waveform continuously regardless of the trigger stability, but only stable
trigger can ensure stable display.
The trigger circuit ensures that every time base sweep or acquisition starts from the input signal and the user-defined
trigger condition, namely every sweep is synchronous to the acquisition and the waveforms acquired overlap to display
stable waveform.
The trigger position is movable on the display. Figure 9.1 demonstrates how the position of the trigger event determines
the reference time point and the delay setting. The acquisition memory is divided into pre-trigger and post-trigger buffers
and the boundary between them is the trigger position.
Before the trigger event arrives, the oscilloscope fills the pre-trigger buffer first, and then continuously updates it in FIFO
mode until the trigger event arrives. After the trigger event, the data fills the post-trigger buffer. When the post-trigger
buffer is full, an acquisition is completed.
Figure 9.1 Acquisition Memory
A trigger setup tells the oscilloscope when to acquire and display data. Trigger setting are based on the features of the
input signal, therefore knowledge of the signal under test is required to quickly capture the desired waveform.
Changes to the trigger setup are applied immediately. If the oscilloscope is stopped when changes are made to the trigger
setup, the oscilloscope uses the new specification when the
Run/Stop or Single key is pressed. If the oscilloscope is
running when changes are made, the oscilloscope uses the new trigger definition when it starts the next acquisition.
The 2560B Series oscilloscopes allow the use of either voltage or current units for waveform measurements.
The remainder of this chapter will refer to just voltages, but it applies to current levels, too.