Oscilloscope and Its Range


by reddvoid
Tags: frequency, oscilloscope, range
reddvoid
reddvoid is offline
#1
Dec20-12, 10:09 PM
P: 99
what happens if we input higher frequency signal to oscilloscope than its range. How will It respond. . .for example in oscilloscope range is 12 MHz how will it display a signal having rise time of say some 40 nano seconds ?
Phys.Org News Partner Engineering news on Phys.org
New ultrasound device may add in detecting risk for heart attack, stroke
Enhanced ground control system and software for small unmanned aircraft
SensaBubble: It's a bubble, but not as we know it (w/ video)
yungman
yungman is offline
#2
Dec20-12, 10:53 PM
P: 3,844
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
berkeman is online now
#3
Dec21-12, 12:06 PM
Mentor
berkeman's Avatar
P: 39,722
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
yungman is offline
#4
Dec21-12, 01:54 PM
P: 3,844

Oscilloscope and Its Range


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.
sophiecentaur
sophiecentaur is offline
#5
Dec22-12, 10:28 AM
Sci Advisor
PF Gold
sophiecentaur's Avatar
P: 11,398
Quote Quote by yungman View Post
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.
Quote Quote by berkeman View Post
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).
Quote Quote by yungman View Post
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.
Definitely!
Basically, there are many worse things possible than just a soggy high frequency response and you can miss all sorts of characteristics of a waveform if you take what you see as the literal truth. Scopes, these days try to think for you and you can lose important features if you take the first picture you see as gospel.


Register to reply

Related Discussions
DC or AC in Oscilloscope. Electrical Engineering 9
Physics projectile problem - finding vertical range using the horizontal range Introductory Physics Homework 1
Is it really oscilloscope? Engineering Systems & Design 1
Looking To Buy Oscilloscope Electrical Engineering 8
oscilloscope Introductory Physics Homework 4