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PG-200 Operation Manual
Version 2.D
programmed on a point by point basis which can become tedious for long sequences
unless implemented through a serial interface.
Pulse sweeping is activated using the “Gate Sweep” program. The program prompts the
user to enter the start delay, the delay step size and the delay step count. Sweeping is
automatically started after the parameters are entered. Sweeping can be de-activated by
either entering a sweep step size of 0, setting a sweep step count < 1, or running the
STOP SEQ program. Sweeping varies from the initial delay to the end delay in
increasing increments (steps). Upon reaching the end delay, a new sweep begins again at
the initial delay.
Pulse Sequences are set up by first clearing out any previous sequences by calling the
CLEAR SEQUENCES program. From then on, sequence points are entered in order by
first setting the PG-200 with the desired gate pulse delay, gate width, DELAYED and
AUX DELAYED TRIGGER out delays and then calling the ADD SEQ PT program. If it
is desired to have no output pulses for a sequence point, the SKIP TRIG program is
selected rather than the ADD SEQ PT program. This feature can be used to “count input
triggers” before producing an output pulse.
Note:
Internal trigger frequency and delayed trigger sync modes cannot be varied during
a sequence. Also, gate pulse width cannot be varied across ranges due to circuit timing
limitations. The three ranges are: <15 nsec, 15-199 nsec, and >200 nsec. The sequence is
activated by calling the START SEQ program.
Both pulse sweeping and sequencing can be deactivated using the STOP SEQ program.
Additionally hitting the “1” key while not in entry mode, e.g., while READY is
displayed, will alternately freeze and unfreeze either sweeping or sequencing.
Automatic System Settings
The PG-200 may require significant instrument setting time delays to perform some of its
tasks. To obtain a gate pulse width range from a few nanoseconds to milliseconds, while
maintaining a constant gate pulse amplitude of about 200 volts, requires a programmable
high voltage power supply. Sometimes when switching between gate pulse widths, the
PG-200 must re-adjust its high voltage supply. If a significant system delay is required,
ADJUSTING HV PS is displayed. In no case should delays exceed several seconds.
Delays are more pronounced for shorter pulse widths, especially for widths less than 15
nsec. Delays will also be observed when changing between width ranges, e.g., from < 15
nsec, to 15-199 nsec, to
200 nsec.
If TIMERS CAL AUTO is enabled, the internal time base is automatically calibrated for
temperature drifts every time the gate pulse width is changed. The larger the time base
drift, the longer the time delay required for calibration, and CALIBRATING TIMERS
may be observed. Worst case calibration time delays can be as much as 10 seconds
although more commonly they should be less than a few seconds.
Another source of instrument setting delay is due to running the PG-200 at near
maximum pulse rates. When maximum rates are reached, much of the system
microprocessor’s time is spent supporting the high pulse rate leaving less time for
servicing user requests. Pulsing tasks are given the highest priority.
In some instances the PG-200 will not accept a user input and will readjust a parameter
to the nearest acceptable value. For example, if a long delay is programmed and that
delay is impossible at a relatively fast internal trigger frequency, the internal trigger
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