Stanford Research Systems DS345, Manual

Page: 38 / 139

Modulation and Sweeps
2-22
TRIGGER GENERATOR
Introduction
The DS345 has an internal trigger generator that triggers BURSTS and SIN-
GLE sweeps from a wide variety of sources. Once a BURST/SWEEP is trig-
gered the DS345 will ignore all triggers until the BURST/SWEEP is complete.
Therefore, a BURST/SWEEP cannot be affected by accidentally triggering
too rapidly.
Trigger Source
Press [SHIFT][TRIG SOURCE] to display the trigger source. Use the MODI-
FY keys to change the source. The choices are:
Source Function
SINGLE The front-panel TRIG key starts the BURST/SWEEP.
RATE The internal rate generator starts the BURST/SWEEP.
POS IN The rising edge of the TRIGGER input starts the BURST/
SWEEP
NEG IN The falling edge of the TRIGGER input starts the BURST/
SWEEP.
LINE The power line frequency starts the BURST/SWEEP.
Trigger Rate
The frequency of the internal trigger rate generator is set by pressing
[SHIFT][TRIG RATE]. The rate may be set to any value in the range 0.001 Hz
to 10 kHz with two digits of resolution.
TRIG'D LED
The TRIG'D LED indicates the DS345's trigger status. Each time a trigger is
accepted the TRIG'D LED flashes green. If the DS345 is triggered again be-
fore the previous BURST/SWEEP is complete, the TRIG'D LED will flash red,
indicating a trigger error. At higher trigger rates a combination of triggers
(green) and trigger errors (red) can make the TRIG'D LED appear orange.
Trigger Input
The rear-panel TRIGGER input is a TTL compatible input. An edge at this in-
put will trigger a BURST/SWEEP if the trigger source is set to POS IN or
NEG IN.
Trigger Output
The rear-panel TRIGGER output is a TTL compatible output that goes high
when the DS345 triggers a BURST/SWEEP, and goes low again when the
BURST/SWEEP is complete. This output is operational for all trigger sources.