On Sat, Apr 30, 2022 at 11:21 PM, si_emi_01 wrote:
Do you have a lot of Overshoot or Undershoot on the waveforms you are
supplying it? On the other scope, what is the Rise and Fall Time? If it is too
fast, since the Impedance is High, it could cause reflections. It says the
Rise/Fall time is less than 10ns.
You are likely been bit by a Signal Integrity issue. The Signal Generator edge
is too fast. With an edge as fast as that is, it needs to be terminated into
the cable Impedance. This isn't possible in your case because the Oscilloscope
Calibration routine expects certain values to be met.
As a test you could use a 50 Ohm in-line Terminator, connect that to the
Oscilloscope Input. Set the Generator for twice the Voltage level (only below
2V to protect your load and Generator), start the test and see if the problem
goes away (as a test only). If it works it is likely caused by Undershoot or
Undershoot. If not, the problem might be somewhere else in the Signal Chain.
I have no overshoot when terminated at 50 Ohms and just a little when at 1 MOhm. So I did the whole vertical calibration using a 50 Ohm terminator plug and then just doubled the voltages from the waveform generator. That worked, although I had to tweak a couple of the voltages to eliminate the dreaded limit error. So I completed the calibration. But more on this below.
