One-Shot Triggering - Keithley 6514 Instruction Manual

One-shot triggering

Other instruments generally have two types of triggering: one-shot and continuous. In one-
shot, each activation of the selected trigger source causes one reading. In continuous, the instru-
ment is idle until the trigger source is activated, at which time it begins taking readings at a spec-
ified rate. Typical trigger sources are:
• IEEE-488 talk
• IEEE-488 Group Execute Trigger (GET)
• "X" command
• External trigger (rear panel BNC)
Arming the instrument to respond to triggers is implicit in the non-SCPI voltmeters. Sending
a command to a non-SCPI voltmeter to change any of the trigger controls causes the instrument
to arm itself for triggers.
The SCPI trigger model implemented in the Model 6514 gives:
• Explicit control over the trigger source (the TRIGger subsystem).
• A way for completely disabling triggers.
Changing any of the settings in the TRIGger subsystem does not automatically arm the
Model 6514 for triggers.
The following program sets up the Model 6514 to take one reading each time it receives an
external trigger pulse.
' For QuickBASIC 4.5 and CEC PC488 interface card, edit
' the following line where the QuickBASIC libraries are
' on your computer:
' $INCLUDE: 'c:\qb45\ieeeqb.bi'
' Initialize the CEC interface as address 21:
CALL initialize(21, 0)
' Puts trigger model in idle state and configure for
' one-shot ' triggering:
CALL SEND(14, "*rst", status%)
CALL SEND(14, "trig:sour tlin; coun inf", status%)
' Take 6514 out of idle (ready for external input triggers):
CALL SEND(14, "init", status%)
After the Model 6514 receives the INITiate command, it stops at the control source in the trig-
ger model, waiting for a trigger pulse. Each time a pulse arrives at the Trigger Link connector,
the Model 6514 takes one reading. Because TRIGger:COUNt has been set to INFinity, the in-
strument never enters the idle state. You can send the ABORt command to put the instrument in
the idle state, disabling triggers until another INITiate command is sent.
Example Programs E-3