The discussion centers on the effects of inputting high-frequency signals into an oscilloscope, particularly when the frequency exceeds the oscilloscope's specified range. Participants explore how oscilloscopes respond to such signals, including potential display issues and signal integrity concerns. The conversation touches on both analog and digital oscilloscopes and their respective behaviors in these scenarios.
Participants express a range of views on how oscilloscopes handle high-frequency signals, indicating that there is no consensus on the exact nature of the response or the implications of the observed behavior.
Participants discuss various limitations related to the oscilloscope's sampling frequency, the potential for aliasing, and the nuances of interpreting displayed waveforms, but these aspects remain unresolved.
yungman said:Usually it just does not displace the full amplitude, the rising and falling edge is slower than the real signal. If the signal is a lot higher in frequency, it might not even display any waveform, but show up as some DC offset.
berkeman said:It can also alias when its sampling frequency is too low for the input signal. That shows up as a nonsense waveform, or it can show up as a low-frequency waveform (which can be very confusing).
yungman said:Yes, I kept thinking about analog scope. For digital scope, you can have beat frequency that you can see low frequency patterns when the input frequency come close to half clock, clock frequency, 2 clock and so on. That's how I test the A to D front end when I was working for LeCroy long time ago. In fact, these are the most important test on how good the ADC is. You see missing codes using these beat frequency technique.