Author Topic: Rigol DG1022Z bug - internal noise source won't freq mod square wave.  (Read 217 times)

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Online Circlotron

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I want to frequency modulate a 100Hz square wave with a random noise source to simulate a chopper disk sensor driven from a piece of machinery subject to vibration and mechanical backlash etc to see how well some firmware deals with this. Set up the DG1022Z and it will allow the 100Hz to be modulated by every other internally generated waveshape except the random noise one. It can be selected but does not actually work. The instruction manual says it can be done. In particular, when the output is set to 100Hz square wave and the FM deviation is stepped up and down between 30Hz and 50Hz in 1Hz increments the 100Hz square wave can clearly heard jumping to different steady frequencies typically 0.5Hz variation. The actual frequency is inconsistent even if the FM deviation is the same on several different occasions.

Can anyone else reproduce this? The firmware is 00.01.12
 

Online Circlotron

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Tried channel 2 as an external modulation source and every waveform works except arbitrary noise. The book says it can be done though...

 

Offline CustomEngineerer

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I'm probably misunderstanding what you are trying to accomplish, but what are you expecting the waveform to look like when you say its not working? I'm pretty sure when you are using noise as the modulating waveform, its modulating at the full max frequency of the generator (notice that the fm frequency setting is not available if the shape is set to noise) and so I would expect the waveform to not really be doing anything other than maybe have a little jitter if you look at the next couple of edges after the trigger.

Edit: I don't have a DG1022Z generator, however this is the behavior I get if I use the built-in generator in my DS2072A-S, and also same with my Siglent SDG-2042X.
 

Online Circlotron

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so I would expect the waveform to not really be doing anything other than maybe have a little jitter if you look at the next couple of edges after the trigger.
That's what I am hoping for - a jittery 100Hz square wave. It sounds quite clean though even with the deviation set to max.
 


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