15
9. COMB OF RAPID PULSES
Demo: with:
DOX2025
DOX2040
DOX2100
DOX2xxxB
Test Signal
n°9 : Comb of rapid pulses
Nature
Comb of 6 very brief pulses, with a low repetition rate
Specs
Vpp ≈ 2 V (depending on whether 50 Ω load or not) - F ≈ 8 kHz
Oscilloscope Settings
25 µs/div., then 10 ns/div. - MAIN = 500 mV/div.
Trigger
on MAIN, 50 % of Vpp
Modes
«LongMem», «Delayed», «ETS»
Objectives
Utility of the ETS for an accurate and precise representation of signals
«Delayed» and «LongMem» mode
a) Adjust the oscilloscope so as to display the pulse trains and a zoomed train of 6 pulses.
Attention, with this type of signal, “Autoset” operation is in principle impossible.
Because of the very brief duration of the pulse (25 ns) compared to their repetition interval (≈ 125 µs), we need a ratio of 1000 between the main
time base and the
“Delayed”
time base.
b) We can also observe the train of 6 pulses in detail in the ETS mode with a 10 ns/div. time base.
The example below presents a train of 6 pulses having a duration < 10 ns with a rise time < 4 ns.
