Scope Over-shoot Measurement

[daveyk]

Look at the attachment.  Any idea why the MSO4104 can not read +Overshoot?  I've tried "full record", "Screen Gating" and cursor gating.  I've compressed the sweep.

The only way I can get it to read +overshoot is to lower the channel amp v/division level (increase scope gain).  But then since the negative part of the signal is clipping, you can get any +overshoot reading you want by varying the channel range.  Once the lower portion does not clip, it no longer reads +over-shoot

The TDS3000 series is better at it, but a lot of the time you must compress the sweep rather heavily for it to read. 

[tautech]

Engage Peak detect in the Acquisition menu ?

[2N3055]

Try longer timebase, to capture two pulses.
Peak measurement is done by establishing max peak level and a "top" of signal plateau, the voltage level of settled signal.
Usually by means of histogram. If settled signal and top signal is same, there is no overshoot. If you have some peak, and then signal settles to some value and stays there, scope takes  those two and calculates overshoot. There are some more things in algorithm, like peak has to come after rising edge etc..

So I presume scope cannot establish clean histogram and is confused.
As I said, try capturing longer period so scope captures two pulses and can see periodicity...

[daveyk]

"Try longer timebase, to capture two pulses."

On the TDS3000 series, that works; not on the MSO4104.  The only thing that seems to work is to set High-Low Method to Histogram.  Of course that looks bad for screen shots as the Fall Time, Pulse Width and +Overshoot measurements all show "Unstable Histogram", but the +overshoot measurement is correct, as is all the other "unstable: measurements.  I wish I could turn off the "unstable Histogram" flags.