Chapter 4 Making Measurements 87
Default Delays If you have not specified a delay interval, the multimeter automatically
determines a delay time (default delay time) based on the present
measurement function, range, resolution, and the AC bandwidth setting. This
delay time is actually the settling time allowed before readings, which
ensures accurate measurements. The default delay time is updated
automatically whenever the function range, resolution, or AC bandwidth
changes. However, once you specify a delay time value, the value does not
change until you execute RESET or a PRESET command, cycle power,
specify another delay value, or default the delay parameter (DELAY -1
command which returns to the automatic delay). The following program uses
the DELAY? query command to respond with the delay time for the PRESET
NORM state.
10 OUTPUT 722;"PRESET NORM"
20 OUTPUT 722;"DELAY?"
30 ENTER 722;A$
40 PRINT A$
50 END
External Triggering The external (EXT) event allows the multimeter to be triggered from an
external source. This event can be used as the trigger arm, the trigger event,
and/or the sample event. The EXT event occurs on a negative edge transition
of a TTL pulse applied to the multimeter's rear panel Ext Trig connector.
The minimum pulse width recognized is 250ns. The bandwidth of the
external trigger circuitry is 5MHz.
The following program uses the EXT event as the trigger event. The sample
event is AUTO; the number of readings per trigger event is set to 1. Upon
the arrival of a negative edge transition on the Ext Trig terminal, the
multimeter takes a reading, which is transferred, to the controller. A second
negative edge transition initiates the second reading, which is transferred to
the controller. This sequence continues until all 20 readings are completed
and transferred to the controller.
10 OPTION BASE 1 !COMPUTER ARRAY NUMBERING STARTS AT 1
20 DIM Rdgs(20) !DIMENSION ARRAY FOR READINGS
30 OUTPUT 722;"PRESET NORM" !TARM AUTO,TRIG SYN, NRDGS l,AUTO,
50 OUTPUT 722;"TRIG EXT" !TRIGGER EACH READING
60 ENTER 722;Rdgs(*) !ENTER READINGS
70 PRINT Rdgs(*) !PRINT READINGS
80 END
Figure 19. DELAY with SWEEP (or TIMER)
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