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Making Measurements
Example 11: Time-Gated Measurement
Table 2-8
Suggested Sweep Times for a Known Pulse Repetition Interval
(PRI) or Pulse Repetition Frequency (PRF)
Pulse Repetition
Interval (PRI)
≤50 µs
100 µs
500 µs
1 ms
5 ms
10 ms
16.7 ms
33.3 ms
50 ms
100 ms
>170 ms
Table 2-9
If You Have a Problem with the Time-Gated Measurement
Symptom
Erratic analyzer trace with
random vertical lines or
dropouts extending below
the peak trace amplitude.
Erratic analyzer trace with
dropouts that are not
removed by increasing
analyzer sweep time;
oscilloscope view of gate
output signal jumps
erratically in time domain.
Gate does not trigger.
Display spectrum does not
change when the gate is
turned on.
152
Pulse Repetition
Frequency (PRF)
≥20 kHz
10 kHz
2 kHz
1 kHz
200 Hz
100 Hz
60 Hz
30 Hz
20 Hz
10 Hz
Use the MAX HOLD trace function and take several measurement sweeps.
Possible Cause
Sweep rate too fast to
ensure at least one gate
occurrence per trace point.
GATE DLY may be greater
than trigger repetition
interval.
Gate trigger voltage may be
too low, or gate may not be
activated.
Insufficient setup time.
Sweep Time (minimum)
50 ms
61 ms
301 ms
601 ms
3.01 s
6.01 s
20 s
30 s
40 s
60 s
Suggested Solution
Increase sweep time until
dropouts disappear.
Reduce GATE DLY until it
is less than trigger interval.
Ensure gate trigger reaches
5.0 volts. Check to see if
other connections to trigger
signal may be reducing
voltage. If using
oscilloscope, check that all
inputs are high impedance,
not 50 Ω.
Increase setup time for the
current resolution
bandwidth, or increase
resolution bandwidth.
Chapter 2
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