Chapter 2 143
Making Measurements
Example 11: Time-Gated Measurement
To make a time-gated measurement:
1. Determine how your signal under test appears in the time domain
and how it is synchronized to the trigger signal.
You need to do this to position the time gate by setting the delay
relative to the trigger signal. To set the delay, you need to know the
timing relationship between the trigger and the signal under test.
Unless you already have a good idea of how the two signals look in
the time domain, you will want to examine the signals with an
oscilloscope to determine the following parameters:
• Trigger type (positive or negative edge of a TTL signal).
• Pulse repetition interval (PRI), which is the length of time
between trigger events.
• Pulse width, or τ. If your signal is not pulsed as in this example, τ
could be as large as the PRI.
• Signal delay (SD), which is the length of time occurring between
the trigger event and when the signal is present and stable. If
your trigger occurs at the same time as the signal, signal delay
will be zero.
Figure 2-74 Time-domain Parameters
In Figure 2-75, the parameters are:
• PRI is 5 ms long.
• Pulse width (τ) is 3 ms long.
• If EDGE POL POS NEG is set to POS, the signal delay is 1 ms
long. (If EDGE POL POS NEG is set to NEG, the signal delay is
0.8 ms long.)
• Gate delay is 2.5 ms long.
• Setup time is 1.5 ms long.
To Next Page
Loading...
Need help?
General
