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AGILENT 35670A
Supplemental Operator’s Guide
60
Section 21 : Using an External Trigger for Time Averaging
Use external triggering for synchronous averaging of linear spectra. With a reliable,
consistent trigger, the resulting noise floor tends to be eliminated and the signal-to-
noise ratio of the measurement can be optimal.
If the trigger is TTL, with little noise and jitter, then trigger setup is accomplished as
follows:
• Press the [Trigger] hardkey.
• Select the [EXTERNAL TRIGGER] softkey (F2).
• Press the [TRIGGER SETUP] softkey (F6)
• Toggle the [EXT LEVEL USER TTL] softkey (F1) until TTL is
highlighted.
Other trigger parameters such as USER EXT LEVEL and EXT RANGE do not need
to be specified when using a TTL trigger.
Specify User Levels for Triggering
When the external trigger is not a TTL signal, the trigger level, slope, and range can
be specified to accommodate a broad range of external triggers. Successful
triggering is easiest to obtain when the external trigger signal is well characterized.
Trigger range, level, and slope must be determined.
Characterizing the External Trigger
External trigger pulses can be noisy and of an unknown shape and amplitude.
Reliable use of an external trigger requires knowledge of trigger characteristics so
that the AGILENT 35670A can be set up properly. This section provides guidance
in capturing and analyzing trigger signals so that reliable external triggering is
attained.
Connect the signal and preset the AGILENT 35670A
• Connect the external trigger signal to Channel 1.
• Turn on the AGILENT 35670A, or
• Press the green [Preset] hardkey
• Press the yellow [Pause/Cont] hardkey if desired.
Select the Histogram/Time measurement mode. This mode turns off the anti-alias
filter so that the actual analog signal can be examined.
• Press the [HISTOGRAM / TIME] softkey (F6).
• Press the [Meas Data] hardkey.
• Press the [UNFILTERD TIME CH 1] softkey (F6).
• Press the [Scale] hardkey.
• Toggle the [AUTOSCALE ON OFF] softkey (F1) until ON is highlighted.