Author Topic: TDS694C Trigger Jitter  (Read 312 times)

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Offline fitch

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TDS694C Trigger Jitter
« on: June 04, 2020, 05:18:51 pm »
Hello all.  I recently obtained a high speed pulse generator just to confirm the BW of my new R&S scope.  But while I was at it, I wanted to see how my old TDS694C did.  What I found is that all channels behave the same and they all exhibit about 40ps peak to peak jitter on the trigger.

I was worried that my scope may have failing trigger ICs, but since all the channels look the same I am not so sure.  Does anyone know what to expect triggering something like this?  The edge rate of the signal is ~ 40ps and it has an amplitude of about 800mV.  Seems to me that sampling at 10GHz means 100ps between samples.  I don't know what kind of games Tek plays with triggering something like this.  Maybe this is the best the scope can do?

What should I expect for trigger jitter?

If my scope is faulty, does anyone know what kind of repair I am looking at?

Thanks!
 

Offline fitch

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Re: TDS694C Trigger Jitter
« Reply #1 on: June 10, 2020, 11:52:19 pm »
Can someone explain how the trigger on a scope like the TDS694C works?  How does the scope know where the analog trigger occurs relative to the discrete samples?

Thanks.
 

Offline madao

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Re: TDS694C Trigger Jitter
« Reply #2 on: June 11, 2020, 03:17:23 am »
Trigger circuit  is  nearly similar with TDS520B, which you can found service-manual with schematic of him.

But i am not sure  by TDS694C. By TDS684C, i am very sure: same trigger-amplifier  & ciruit.

 

Offline KE5FX

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Re: TDS694C Trigger Jitter
« Reply #3 on: June 11, 2020, 04:15:28 am »
Does it look like this?



If so, they all do that.  Not much is known about the inner workings of these things, but the lack of Nyquist margin probably doesn't help much.
 

Offline fitch

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Re: TDS694C Trigger Jitter
« Reply #4 on: June 11, 2020, 11:50:36 pm »
Similar, but I see much more jitter than I see on your scope.  I guess I could have posted this earlier.  The trigger appears to be a constant voltage, but the display seems to have some horizontal (time) noise in it.  The signal I am sampling has a low duty cycle and I am only capturing a single screen worth of data.  As I stated earlier, all 4 channels behave the same, so either they are all working, or something common to them all is broken.
« Last Edit: June 11, 2020, 11:56:18 pm by fitch »
 


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