Keithley 2520, User Manual, Page: 128 / 329

8-12 Triggering Model 2520 User’s Manual
Delay and pulse phases
The delay-pulse cycle consists of two phases: Delay and Pulse. (See Section 5 for details.)
Delay phase
The programmable delay is the time period between current pulses. The delay is set with
the :DELay commands and can be programmed in the range of 20
µ
s to 500ms. Note, how-
ever, that the programmed delay is the minimum delay, and the actual delay depends on
the pulse duty cycle (see
Section 5 ).
Pulse phase
During the pulse phase, the unit outputs one current pulse with the programmed pulse
width (set to between 500ns and 5ms with the :WIDTh commands). If the unit is in the
fixed (non-sweep mode), the pulse amplitude is the same for each cycle through the loop.
However, if the unit is the sweep mode, the pulse amplitude is set to the programmed
value for that sweep point. 10MHz samples are taken during the pulse phase, and one set
of voltage and current readings is DSP processed for each pulse.
Filtering
If the filter is enabled, the instrument cycles through the delay-pulse loop for the pro-
grammed filter count and averages the specified number of readings to yield a single set of
filtered readings (measurements).
Sweep points
When a sweep is enabled, the unit cycles through the complete delay-pulse process
(including filtering if enabled) for the programmed number of sweep points. For linear
staircase sweeps, the number of points depends on the start, stop, and step current values.
For log staircase sweeps, the number of points depends on the start and stop current values
and the programmed number of points. For custom sweeps, the number of points depends
on the length of the sweep current list.
Counter
The programmable counter is used to repeat operations within the Trigger Layer. For
example, to repeat a sweep three times, the trigger counter would be set to 3. If the sweep
has a total of 10 points, a total of 30 measurements will be made.
The maximum finite trigger counter value is 5000. However, the product of the trigger
count and the number of sweep points cannot exceed 5000.