User Manual

Sampling oscill
oscope concepts
Trigger type Trigger conditions
Edge Edge triggers are the simplest and most commonly used trigger
type. An edge trigger event occurs when the trigger source passes
through a spec
ified voltage threshold (trigger level) when the signal
is transitioning in the specified slope (rising or falling).
You can trigger on a rising or falling edge, as defined by the slope
control.
Pulse
Width
You can trigger on pulses that are less than, greater than, equal to,
or not equal to a specified time period. You can trigger on positive
or negative p
ulses.
Pulse width triggers are primarily used to analyze digital signals.
Runt
A runt puls
e is a pulse that crosses one threshold but fails to cross
a second threshold before recrossing the first. Therefore, a runt
trigger needs two thresholds to define the two levels that a signal
must pass
through to be considered a valid (nonrunt) signal.
You can trigger on any positive or negative (or either) runt signal.
You can also trigger on runt signals with pulse widths that are less
than, gre
ater than, equal to, or not equal to a specified width.
Runt triggers are primarily used to analyze digital signals.
Trigger
coupling
Trigger coupling sets what part of the input signal is used by the trigger circuit. Trigger coupling choices are DC, LF Reject,
HF Reject, and Noise Reject.
DC C oupling passes the trigger signal to the trigger circuit with no filtering. The scope may trigger on false events if
the signal is noisy.
HF Reject blocks signals above 85 kHz from the trigger circuit. This reduces false triggering on high-frequency noise
when measuring lower-frequency signals.
LF Reject blocks signals below 65 kHz from the trigger circuit. This reduces false triggering from low frequency noise
when measuring higher-frequency signals.
Noise R eject reduces the trigger circuit input sensitivity. This reduces false triggering when measuring signals with
higher levels of noise.
Trigger modes
The Trigger Mode sets how the oscilloscope behaves in the absence o r presence of a trigger. Trigger mode also enables
the
trigger holdoff function.
Auto (Untriggered Roll) trigger mode. The Auto (Untriggered Roll) mode sets the oscilloscope to acquire a
waveform even if a trigger does not occur. Auto mode uses a timer that starts when the acquisition is started, and the
pretrigger information is obtained. If a trigger event is not detected before the timer times out, the oscilloscope forces a
trigger. The length of time it waits for a trigger event depends on the time base setting (Horizontal Scale).
28 TBS2000 Series User Manual