Author Topic: Rigol 1054 triggering  (Read 1079 times)

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Offline sndchaser

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Rigol 1054 triggering
« on: September 25, 2016, 11:41:50 AM »
Question with a problem (likely user error) I'm having with my Rigol 1054 that I didn't have with my Tektronix scopes.  I'm edge triggering, have the trigger level set, and on some signals I get the expected triggering (1st picture) and on others I get a blur (like the other pictures).  I'd appreciate it if someone could point out what I'm doing wrong.  Thanks
 

Offline evb149

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Re: Rigol 1054 triggering
« Reply #1 on: September 25, 2016, 11:54:40 AM »
I think your sweep should be "normal" and not "auto" if you are expecting to be manually controlling the triggering settings.
I could be wrong since I'm not extremely well versed with the Rigol settings at this point though I successfully use them when I have a need to, I don't recall all the specific ways they have implemented things.  For instance I don't recall what "auto" really "automates" and based on what criteria.

Also On the "blurred" shots you do seem to have a rising edge at the trigger position so it is cenetering the trigger event around the expected channel, level, and edge.  But that does not mean that SOMETIMES there are ALSO edges at other positions within the waveform that will show additional edges at other locations relative to the trigger point.
Depending on your persistence setting and so on you could well be seeing the presence of intermittently occurring edges that happen at some other positions relative to the trigger point and they are faint and unstable because perhaps in reality the other edges do not always occur in such positions but the composite waveform you see may be an accumulation of various captures some of which had additional edges besides the one used to trigger.

 

Offline sndchaser

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Re: Rigol 1054 triggering
« Reply #2 on: September 25, 2016, 12:06:07 PM »
Persistence is on Min.  I put it on normal triggering and still get the blur.  With single triggering I see that my duty cycle is irregular, so I guess this triggering behavior for auto and normal is as intended? 
« Last Edit: September 25, 2016, 12:17:11 PM by sndchaser »
 

Offline tautech

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Re: Rigol 1054 triggering
« Reply #3 on: September 25, 2016, 12:22:32 PM »
I put it on normal triggering and still get the blur.  With single triggering I see that my duty cycle is irregular, so I guess this triggering behavior for auto and normal is as intended?

This looks like a data stream and your rising edge triggering probably isn't helping for a negative going signal.
Also if it is a data stream it's not a repetitive waveform and therefore triggering will not be stable without additional trigger parameters being set.
The clue is a blurry waveform that it's not repetitive and confirmed with the Single shot.
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Offline evb149

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Re: Rigol 1054 triggering
« Reply #4 on: September 25, 2016, 12:26:58 PM »
Yes, it sounds like it is all working as intended given that those other edge positions do sometimes occur with your waveform input.  The DSO is just showing those to you over time and triggered captures except when in single shot mode in which case it will show only the one capture sequence and whatever other edges that contains.

 
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Offline sndchaser

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Re: Rigol 1054 triggering
« Reply #5 on: September 25, 2016, 12:27:42 PM »
Surprisingly, it's actually not a data stream, it's an apparently defective frequency divider IC (it should take the 500kHz signal from the stable shot and divide it down to each frequency in an octave of musical notes).  I've seen the blur on other analog signals with this scope, just curious what other triggering parameters I could be trying to get stable triggering?
 

Online Fungus

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Re: Rigol 1054 triggering
« Reply #6 on: September 25, 2016, 03:37:47 PM »
just curious what other triggering parameters I could be trying to get stable triggering?

Your trigger is stable. It's the signal that's wonky.



If you pick a random rising edge in that signal then the data on either side is unpredictable.
 

Offline evb149

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Re: Rigol 1054 triggering
« Reply #7 on: September 25, 2016, 03:50:33 PM »
Yeah it is doing what you asked it to do.  When it is ready to retrigger to find some rising edge at some level and then trigger.  So it picks whatever one is next after it is ready to retrigger, and that's the one it gets.  What comes before and after it is up to your circuit.  There's little likelihood that the triggering is picking the "same" edge of the signal that is with respect to the signal's periodicity if the signal is, in fact, periodic.

I'm going out on a limb here but are you sure that you understand what your frequency divider chip is supposed to be putting out?  That sort of modulated width signal almost looks like it could be some sort of PDM or PWM or something so it made me wonder if the "frequency" it is putting out could just be something like an analog signal that has to be reconstructed by a filter to convert 1-bit digital PDM/PWM/whatever into the desired sinewave.
Anyway I assume it isn't the case since the widths of the pulses you captured looked like they're often quite a few microseconds wide which would be kind of slow for a high fidelity sampled audio bitstream that would usually be at several Mbit/second rates and up...but..maybe.

I guess it could be putting out I2S or something too..but anyway it is odd if a pin of a chip is putting out an actively modulated signal that is nothing at all like what you expect it to be.  Usually that means either you're on the wrong pin, or the IC is set into some other operational mode than you expect, or you're misunderstanding something about the interface...
 
Surprisingly, it's actually not a data stream, it's an apparently defective frequency divider IC (it should take the 500kHz signal from the stable shot and divide it down to each frequency in an octave of musical notes).  I've seen the blur on other analog signals with this scope, just curious what other triggering parameters I could be trying to get stable triggering?
 

Offline sndchaser

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Re: Rigol 1054 triggering
« Reply #8 on: September 25, 2016, 08:51:32 PM »
Yes, the chip is an MK50240 from the 1970's:

http://www.datasheetspdf.com/datasheet/MK50240.html

It really just divides a square wave into 13 slower square waves.   Way before I2S was even dreamed of.   The triggering wasn't working as I expected it to because the chip has failed. 
 

Offline David Hess

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Re: Rigol 1054 triggering
« Reply #9 on: September 26, 2016, 06:30:53 AM »
Automatic triggering just means that after a period of time without a valid trigger, the acquisition or sweep is started anyway so at least something is displayed.  Normal triggering always waits for a valid trigger.  On a Tektronix you can check this condition via the trigger indicator; I don't know if Rigol includes this.

You should have gotten the same results with a Rigol or Tektronix oscilloscope.
 


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