Hello Forum,
I have come across an issue while attempting to view two sine wave outputs simultaneously, sort of. The key players are as follows:
Output 1
CH1 - Generic fleaBay GPSDO 10Mhz oscillator.
CH2 - MSOX-2024A WaveGen
I have adjusted the Vpp level for CH2 so that it is near / at the same Vpp level as the GPSDO source. Both inputs are running at HighZ. No matter what combination of triggering, delay, tongue angle or moon phase I am unable to get the built in WaveGen to display a nice sinusoidal wave form (see attachments). It gets interesting from here if I remove the source CH1. Even terminating both inputs at 50Ω does not solve the issue.
Output 2
CH1 - MSOX-2024A WaveGen
CH2 - Rigol AWG (DG1022)
In this setup I am able to view both sine waves without issue and visually see the difference as the phase shift marches back and forth. This has me stumped, but not defeated. Am I missing something key here? I would really like to utilize the GPSDO as a reference wave form due to the stability and accuracy of the output.
Any assistance is most appreciated.
Regards,
Chris
I don't see a problem with either picture. The difference has to do with the ability of a scope to capture and display data quickly. 'Output 1' shows thescope that can capturing and displaying a lot more screen updates quickly. It is showing about fifty fast acquisitions on the screen at once, and the green trace is moving across the screen, due to phase shift. The built-in persistence, even set at 'off' or minimum, will show multiple waveforms overlaid. If you switch to 'Single' mode and hit the Single button as fast as you can, will see the relative locations of the waveforms changing, too.
I don't know why one waveform looks more stable than the other, but they are both accurate.
BTW, you should almost never use HighZ inputs or outputs. Most outputs are 50 Ohm, the cables are 50 Ohm, so the input should also be 50 Ohm. HighZ -> 50Ohm will give you bad results. 50 Ohms -> HighZ will give you bad results. Be consistent. That said, there are times when you might want to use HighZ inputs. You might have two inputs that you want to connect to a 50 Ohm output. In that case, you might set one of the inputs to HighZ and the other to 50 Ohm, so the output sees a 50 Ohm load.