20
PG-200 Operation Manual
Version 2.D
➧
To set up a sweep, run the GATE SWEEP program by pressing “F” (Function), “1”,
and “E” (Enter). The screen will prompt you in turn for:
The starting gate delay
e.g., 50 nsec
The gate delay sweep step size
e.g., 1 nsec
The gate delay sweep step count
e.g., 1000
➧
When this program is complete, the screen will say READY and you will be able to
observe the gate pulse delay increase from 50 nanoseconds after the trigger for the
first pulse to about 1.05 microsecond after the trigger for the last pulse (pulse 1000).
Since pulses are being produced at 3000 per second (the internal trigger frequency
set in step # 14), and you have just specified 1000 steps in the sweep, each sweep
will take about a third of a second. To stop the sweeping, run the program again and
set the step count to 0.
➧
Note that when you set the step size to 1 nsec, the PG-200 may respond with a step
size that is slightly different, e.g., 0.92 nsec, depending on calibration.
PG-200 Triggered by an External Source
In some experiments, the pulser will not be the source of timing. Instead it will respond
to timing signals from other devices such as a laser or another pulse generator. To trigger
the PG-200 from an external source:
➧
Press the Trigger Select key. This key toggles the trigger source between internal and
external and the corresponding LED on the front panel will light to show the mode
selected.
➧
Connect the trigger signal to the Trigger Input on the front panel of the instrument.
The AC/DC coupling, trigger level, ± trigger polarity and input impedance controls
operate like those on an oscilloscope. When the PG-200 is being triggered by the
external signal, the Triggered LED will light up.
➧
The trigger input to the PG-200 should also be connected to your oscilloscope, as the
internal trigger output, previously connected, is no longer relevant.
➧
Each time the PG-200 is triggered, the oscilloscope should now show you the pulse.
Trigger Modes
In external trigger mode, there is a choice of electrical or optical inputs. The external
trigger section of the PG-200 front panel is similar to that of an oscilloscope. It has input
impedance select, AC/DC coupling select, ± polarity select, and a level potentiometer
adjustment. The level pot can be monitored by pressing the TRIGGER LEVEL key. The
trigger detector operates on inputs from +10 V to –10 V. Although it may accept trigger
signals of greater amplitude without damage, depending on the input impedance setting
and the input signal duty cycle, the pulser may trigger erratically and in some cases
damage may result. For these reasons, do not exceed 10 volts peak input to the trigger
detector.
For optical external trigger inputs, the impedance select switch must be set for 50 ± and
the trigger polarity for negative. Trigger level must be set below 0 V, e.g., –1 V. The
trigger signal should have as fast a leading edge as possible, preferably less than 5 nsec.
Slow leading edges increase the trigger jitter. The trigger detector will normally work
well with all TTL types as trigger sources. If the 50 ± external trigger input impedance is
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