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3 - 20 USING THE COMBISCOPE INSTRUMENTS
3.4.1.1 Triggering
After the measurement is initiated, the CombiScope instrument starts the real
acquisition when the trigger conditions are satisfied, e.g., when the selected
trigger event occurs. The trigger conditions can be ignored during a specific hold-
off time, which can be programmed using the TRIGger:HOLDoff command.
During the hold-off time the event detector is inhibited from acting on any trigger.
Trigger Type
The TRIGger:TYPE command selects the type of triggering, which can be
programmed to EDGE triggering (normal trigger mode), VIDeo triggering (refer to
section 3.4.1.2 "Video triggering"), LOGic, or GLITch triggering. After a
*
RST
command, the trigger type is EDGE.
Note: Logic state, pattern, or glitch settings cannot be programmed using SCPI
commands.
Trigger Source
The TRIGger:SOURce command selects the source for the trigger event. The
receipt of the GPIB interface message GET (Group Execute Trigger) or the
common command
*
TRG serves as the trigger event when BUS is selected as
trigger source.
The trigger event is determined by the AC line voltage when LINE is selected, and
is derived from the input signal when INTernal is programmed as trigger source.
For the 2-channel CombiScope instruments, EXTernal can be programmed as the
trigger source. In that case, channel 4 is selected as external trigger input.
A numeric suffix is used to specify the channel number. For example,
TRIGger:SOURce INT2 selects the signal at input channel 2 to trigger the
acquisition.
When IMMediate is selected, an acquisition does not wait for a trigger event. So,
an INITiate command causes the acquisition to begin immediately. After a
*
RST
command, the trigger source is IMMediate, which means no trigger is required.
Trigger Level
The TRIGger:LEVel command allows you to set the trigger level for all input
channels. Programming the trigger level automatically switches off level peak-
peak. The trigger level can be programmed only when the TRIGger:SOURce is
INTernal. The TRIGger:LEVel:AUTO command allows you to switch level peak-
peak on or off. Switching on level peak-peak, deactivates the trigger level. After a
*
RST command the TRIGger:LEVel is set to its maximum value and level peak-
peak is switched off.