Author Topic: DG1022Z amplitude jumps slightly with frequency change  (Read 682 times)

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Offline Circlotron

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DG1022Z amplitude jumps slightly with frequency change
« on: May 25, 2018, 09:40:31 pm »
Rigol DG1022Z function generator set to 10v p/p sinewave.
If I go from 100,000 Hz to 100,000.000,001 Hz the output voltage increases by approx 200mV p/p. Both channels do the same. Anyone else noticed this?
 

Offline Gandalf_Sr

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #1 on: May 31, 2018, 08:13:57 pm »
I have a DG1022Z, how are you doing the measurement?
 

Offline exe

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #2 on: May 31, 2018, 09:11:17 pm »
How do you measure?

Anyway, there are many reasons, including resonance, incorrect measurements, calibration, etc.

PS I don't get what "100,000.000,001 Hz" means. Is it 100kHz?
 

Offline Gandalf_Sr

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #3 on: May 31, 2018, 09:45:36 pm »
So I just ran a test; 50 Ohm output set on the DG1022Z, 5 Vpp into a 50 Ohm coupler on my DS1054Z.  When I went from 100,000.000,000 Hz to 100,000.000,001 Hz, the output decreased from 5.04 Vpp to 4.92 Vpp, a difference of 120 mVpp.  It's a definite change that occurs at that specific point, leading up to and after the point, the voltage is steady.

There's probably some lookup table that switches over at this point but I'm unconcerned.  What I typically do is set up the DG1022Z to close to what I want and then monitor the voltage applied at the point of insertion using an accurate multimeter while tweaking the controls to make sure the input is at the desired parameters.
« Last Edit: May 31, 2018, 09:47:19 pm by Gandalf_Sr »
 

Offline Circlotron

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #4 on: May 31, 2018, 10:01:24 pm »
I just had a 1 metre length of coax from the sig gen with alligator clips on the end, clipped to the X10 scope probe. Not terminated or anything. I’m not particularly fussed about it, just hoping someone for Rigol reads these columns and somehow gets included in a firmware update.
 

Offline Circlotron

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #5 on: May 31, 2018, 10:03:33 pm »
PS I don't get what "100,000.000,001 Hz" means. Is it 100kHz?
Very very slightly higher than 100kHz
 

Offline Gandalf_Sr

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #6 on: May 31, 2018, 10:13:50 pm »
So I confirmed the issue you identified - maybe Rigol will look at it, maybe not. 

I'm surprised no one has figured out how to unlock it to be a 1032 or 1062 yet.
 

Offline exe

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #7 on: May 31, 2018, 10:33:46 pm »
I think it's a calibration issue. In "DG1022 Function/Arbitrary Waveform Generator Calibration Guide" everything up to 100kHz is low frequency and calibrated separately. See "Low Frequency Flatness Adjustment" and "Range Flatness Adjustment".

Keep in mind higher frequencies are calibrated with 50 Ohm load.

Disclaimer: I have zero experience in calibration.
 

Offline seronday

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #8 on: June 08, 2018, 08:08:54 pm »
I have seen this same level change above 100Khz happen with a Rigol DG4062.
In this case it was within the specified +/- 0.1dB Flatness into a 50 ohm load.

I suspect that it is related to the internal calibration table.

Regards.
 

Offline Circlotron

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #9 on: June 08, 2018, 09:36:53 pm »
In "DG1022 Function/Arbitrary Waveform Generator Calibration Guide"
Where can we find this publication?
 

Offline exe

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #10 on: June 09, 2018, 02:57:57 am »
Where can we find this publication?

Uhm, first link in google :).
 

Offline Circlotron

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #11 on: June 09, 2018, 08:04:38 am »
When I looked (before I asked)  it only referenced this thread. I’ll have to try again!
 

Offline exe

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Offline bd139

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Re: DG1022Z amplitude jumps slightly with frequency change
« Reply #13 on: June 09, 2018, 10:25:38 pm »
My fresh out of the box new DG1022Z this morning does the same. Drops 25mV on Hi-Z input but only 1mV on 50 ohm load ergo this looks like it's calibrated for a 50 ohm load.
 


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