Hi, I have a Tektronix 7704A oscilloscope with both a 7B80 time base and a
7B53A dual time base. The 7B53A dual time base plugs into a slot labeled "A
horiz (delaying time base). What is the dual time base used for? I really
don't want to use it, for now, and I'd like to not worry about setting it up
or having it influence measurements.
Thanks -Ira
A delayed sweep function is used for viewing short duration events on
signals with long periods. For example, you want to observe a single
low amplitude noise pulse out of many that occur somewhere in the
middle of a high amplitude periodic signal. If you trigger on the
main signal, you can't see the details of the noise pulse. You could
try using AC coupled triggering to trigger on the noise pulse, but you
can't control which of the noise pulses the 'scope will trigger on.
Enter the delayed sweep 'scope: You set up the delayed sweep timebase
(the one in the right hand slot) such that its sweep frequency is
appropriate for viewing the noise pulse. The delaying time base
allows you to delay the triggering of the delayed sweep by an amount
equal to the time between the trigger point of the main signal and the
time at which the noise pulse occurs. At that time, the delayed sweep
triggers, allowing the noise pulse to be observed at a fast sweep rate
on the 2nd channel of the 'scope. The portion of the waveform that is
viewable by the delayed sweep is displayed as an enhanced brightness
on the trace. By adjusting the delay time knob, you can move this
enhanced brighness traces back and forth until it spans the noise
pulse. By not selecting the delayed sweep feature, you can use the
'scope as a normal 'scope..
