External Trigger And Stop Sweep Signals - HP 8510 User Manual

If you are viewing this with an oscilloscope, notice how the measurement cycle time varies
according to the pulse pro le stop time. If the stop time is greater than the pulse width, the
measurement cycle time will extend past the end of the pulse depending upon the time value
of the data point being measured. Depending upon the pulse width, this can result in a lower
percent duty cycle toward the end of the time span.

External Trigger and Stop Sweep Signals

Figure 8-3 shows the relationship between the external Trigger Input and the HP 8510 Stop
Sweep output for frequency domain point-in-pulse measurements and for pulse pro le domain
measurements. For external triggering, Stop Sweep remains Busy (low) until the measurement
cycle is complete. This information is important for synchronizing the pulse modulation to the
external trigger.
It is easy to learn the timing by using an oscilloscope to view Stop Sweep when the external
trigger is applied.
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Press and apply a TTL pulse
MORE TRIGGER MODE TRIGGERING EXTERNAL
4 STIMULUS MENU 5
train to the HP 8510 rear panel EXTERNAL TRIGGER INPUT. The trigger should stay low
for at least 100 nanoseconds. Excess triggers that occur while stop sweep is busy (low) are
ignored. The next external trigger falling edge after stop sweep is ready will initiate the next
measurement cycle and retrace is automatic.
Figure 8-3. External Trigger and Stop Sweep Timing Diagram
General Timing Information 8-5