Suggested by mmame on the EEVblog forum. Thank you!
| Roll off | One tap: Roll Off, and a triggered trace at 500 ms/div |
| Live sweep | Before the edge at once, after it as it is sampled |
| Holdoff | A burst triggers once, at its first edge, with holdoff up to 10 s |
| Trigger in roll | SINGLE and NORMAL trigger in roll |
The Acquire sheet's Roll row is one choice: Off, On or Auto. Off keeps the scope in its normal time mode at every time base, 50 ms/div and slower included, with the trigger working as it does at fast ones: every trigger type, AUTO, NORMAL and SINGLE, and the holdoff. The choice is kept across power cycles. Auto rolls from 50 ms/div, or from any time base between 5 and 100 ms/div set beside it, and triggers below it. Over SCPI: :TIMebase:ROLL OFF and :TIMebase:MODE MAIN.
At 200 ms/div and slower, an edge trigger on an analog channel does not make you wait for a whole record of 2 s or more. The part before the trigger point appears the moment the edge comes, and the part after it is drawn left to right as it is sampled, with the edge held at the trigger point and the horizontal position setting the split. SINGLE stops when the screen is full. In AUTO a screen is drawn untriggered when no edge comes within half a second; NORMAL waits.
The trigger holdoff applies between these sweeps as it does at fast time bases: after a trigger the next edge counts only once the holdoff has passed, so a burst of edges starts one sweep, at its first edge. AUTO's untriggered screen waits for the holdoff as well.
Roll and the trigger are also chosen apart. In roll, SINGLE rolls until the edge, then on until it reaches the trigger point, and stops there; NORMAL holds each triggered screen for a moment; AUTO rolls freely.
The acquisition's tests check the holdoff at slow time bases: with a holdoff longer than the signal's period, a sweep starts only at the first edge after the holdoff.
Our DHO924S rolling at 500 ms/div, then Roll Off and SINGLE catching a slow square from its own generator, with the edge at the trigger point.
Which scope you use and what you trigger on at slow time bases (a supply ramping up, a slow serial line, a sensor), so we can test that case on our bench.
A normal trigger at slow time bases, 50 ms/div and slower, with roll mode turned off.
The only feature I missed in the stock fw is trigger support for slow signals (so: to disable roll mode)
Try it and tell us what to change: reply on NovaOS's thread on the EEVblog forum.