FAQs from Rohde & Schwarz

No synchronisation in Auto Trigger Mode


With my scope i have problems to detect pulses correctly. The pulse repetition rate is longer than 500 ms. Sometimes I see just a flat trace, no pulses are shown for many seconds. And sometimes it seems to work correct for some seconds before the problem comes up again.


That effect comes up if the trigger mode “Auto” is used. If no trigger condition is detected for 500 ms, the instrument triggers. That helps to see the waveform if no correct trigger condition is set. If the repetition rate is a little bit longer than 500 ms a kind of “interference” comes up, because there is no synchronization to the signal. The trigger will sometimes catch the pulse, sometimes not.

The only way to overcome that effect is to use the “normal” trigger mode. Then a trigger is done only when the condition (which is set by the user) is detected.