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[Moved]: Using an external clock for oscilloscope

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venn_ng

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Hi,

I am using an external reference clock (channel 2) for plotting a signal (channel 1) on the scope. Now, the external reference is in sync with the signal, as they are coming from a single IC. The question that I have is that would the external reference clock be filtered by the scope (say, using a PLL) when it's actually plotting the signal with respect to the external reference. What actually goes on generally inside the scope for the external reference clock generally?
 

Re: Using an external clock for oscilloscope

What do you mean by external "reference clock"?

The second signal can either act as trigger in regular time base sweep or as x input in x-y mode.
 

Re: Using an external clock for oscilloscope

It's a clock derived from a PLL that is clocking the signal as well. I am sending the signal and this clk to two channels in the scope. I would like to know if the oscilloscope filters that external reference clk (clk derived from the PLL) while doing regular time base sweep (like, what's the bandwidth that it filters out generally)?
 
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Re: Using an external clock for oscilloscope

Are you feeding two identical signals to an XY plot? Then the beam creates a single line moving between upper R and lower L. You do not get the normal left-to-right sweep.

Or are you feeding one signal to the scope as an external trigger? Then the beam starts a left-to-right sweep whenever the external trigger signal changes sufficiently.
 
Re: Using an external clock for oscilloscope

Hi,

I recommend to consult the scope's manual.

Then you will face the same problem that we do we your vague description.
Example:
You say:
I am using an external reference clock (channel 2)
Click to expand...
But there usually is no "external reference clock (channel 2) input at a scope"
* either you talk about channel2 input
* or you talk about external trigger input
* or you have a "special" scope
We don't know the answer. And guessing is a waste of time, for us and for you, too.

So give more precise informations. Use the same terminology for the inputs as mentioned in the manual.
Give the scope's type and manufacturer.
Give the IC name and the signal names or pin names you refer to.
And so on.

Klaus
 

Re: Using an external clock for oscilloscope

Hi Brad,

Thanks. I guess this answers the question. I am using it as an external trigger. I was thinking that it would be passed through a filter, but it looks like that's not the case.
 

I am using it as an external trigger.
Click to expand...
Using commonly understood terminology helps to better understand your question.

Recent oscilloscopes have some filter options for the trigger, e.g. RF rejection, low frequency rejection. But hardly a PLL.
 

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