Oscilloscope questions: More than one frequency or RF

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
Hi. I'm looking for some basic info on Oscilloscopes to help understand testing equipment.

If multiple signals are connected to a OS ,does it show the different waves combined into one wave?
 

MrChips

Joined Oct 2, 2009
20,914
Hi. I'm looking for some basic info on Oscilloscopes to help understand testing equipment.

If multiple signals are connected to a OS ,does it show the different waves combined into one wave?
Yes.
One channel input can only see the total sum of all signals coming to that channel. It is like getting multiple sounds and voices coming into one ear. Many oscilloscopes have two input channels so that you can look at two signals simultaneously. More expensive oscilloscopes have four input channels.
 

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
So you really need a spectrum analyzer to be able to differentiate between multiple frequencies combined into ONE or a SINGLE signal that is alternating in frequency (frequency changing)? Would both of these instances look the same on a OS.
Thank you for your expertise!
 

dl324

Joined Mar 30, 2015
10,536
If multiple signals are connected to a OS ,does it show the different waves combined into one wave?
On scopes with multiple channels, you have one trace per channel. My scope can have up to 8 for analog and up to 16 for digital (logic analyzer plug-in).
 

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
I really don't have a specific thing I want to do but know how a OS would behave.
What if a one channel OS is connected to a antenna? With out a filter or something the OS is going to be subjected to multiple frequencies. As a OS cannot sepparate the different frequencies ,I would assume that it represents it in one wave that is a combination of the separate frequencies and or waves. Overlapping waves for example would have to be combined into a single wave.
 

MrChips

Joined Oct 2, 2009
20,914
I really don't have a specific thing I want to do but know how a OS would behave.
What if a one channel OS is connected to a antenna? With out a filter or something the OS is going to be subjected to multiple frequencies. As a OS cannot sepparate the different frequencies ,I would assume that it represents it in one wave that is a combination of the separate frequencies and or waves. Overlapping waves for example would have to be combined into a single wave.
The signals picked up by an antenna are in μV ranges. The input to the scope goes as low as mV. You are not going to see much except 60Hz line pickup.
 

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
Thanks for that enlightenment. I'll have to give those aspects more thought. What about 3 phase A/C power. How would a single channel OS represent that?
 

MrChips

Joined Oct 2, 2009
20,914
Here is specific example.
Music created by a 50-piece orchestra is picked up by a single microphone. The signal is amplified and viewed on an oscilloscope. Here is an example of what one would see.

1590172506461.png
 

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
Disregard the 3 phase questions as I have learned that they are measured individually.

If the sound image was over a shorter period of time I think I would understand it.
Lets say that only two separate ,single frequency waves are connected to a single channel OS. If the peaks were at the same instance, would the OS show a single wave with a combined voltage? If one wave was at peak and the other at zero ,would the OS represent that instance as a average of the two?
 

dl324

Joined Mar 30, 2015
10,536
would the OS show a single wave with a combined voltage?
It would be helpful if you used the usual and customary terminology. You could call it a scope, but OS has other meanings (Operating System always comes to mind first for me).

To satisfy my curiosity, I searched for meanings of OS. There were 115 and oscilloscope wasn't among them. The top three were:
clipimage.jpg
 
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tautech

Joined Oct 8, 2019
90
I really don't have a specific thing I want to do but know how a OS would behave.
What if a one channel OS is connected to a antenna? With out a filter or something the OS is going to be subjected to multiple frequencies. As a OS cannot sepparate the different frequencies ,I would assume that it represents it in one wave that is a combination of the separate frequencies and or waves. Overlapping waves for example would have to be combined into a single wave.
This really is spectrum analyser territory however the modern DSO with good FFT can identify the individual signals and express them in amplitude.
 

MrChips

Joined Oct 2, 2009
20,914
I should add, of interest to musicians, other strange things happen.
With musical instruments you can clearly hear sum and difference frequencies.

sin(A) + sin(B) = 2 sin( (A+B)/2 ) x cos( (A-B)/2 )
 

dl324

Joined Mar 30, 2015
10,536
By deduction OS can only mean oscilloscope.....not really that hard to type. ;)
OS is not commonly understood to mean oscilloscope. Until today, I don't think I've ever seen OS used to refer to a scope. CRO maybe, but not OS.

https://simple.wikipedia.org/wiki/Oscilloscope

If you're tempted to use O-scope, just use scope; it's easier to type. The people I worked with just called them scopes. Scope probe, scope cart, scope camera, just scope...
 
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nsaspook

Joined Aug 27, 2009
7,186
OS is not commonly understood to mean oscilloscope. Until today, I don't think I've ever seen OS used to refer to a scope. CRO maybe, but not OS.

https://simple.wikipedia.org/wiki/Oscilloscope

If you're tempted to use O-scope, just use scope; it's easier to type. The people I worked with just called them scopes. Scope probe, scope cart, scope camera, just scope...
I've seen OS being used in ancient times before but it's not common today and would definitely need a signal measurement context to make the connection. My first CRO was a OS-8 that's still at my mom's house in Texas.

https://blogs.telosalliance.com/found-in-the-attic-os-8/u-oscilloscope
 
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