# EEVblog Electronics Community Forum

## Products => Test Equipment => Topic started by: Circlotron on May 25, 2018, 11:40:31 am

Title: DG1022Z amplitude jumps slightly with frequency change
Post by: Circlotron on May 25, 2018, 11:40:31 am
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?
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Gandalf_Sr on May 31, 2018, 10:13:57 am
I have a DG1022Z, how are you doing the measurement?
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: exe on May 31, 2018, 11:11:17 am
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?
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Gandalf_Sr on May 31, 2018, 11:45:36 am
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.
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Circlotron on May 31, 2018, 12:01:24 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.
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Circlotron on May 31, 2018, 12:03:33 pm
PS I don't get what "100,000.000,001 Hz" means. Is it 100kHz?
Very very slightly higher than 100kHz
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Gandalf_Sr on May 31, 2018, 12:13:50 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.
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: exe on May 31, 2018, 12:33:46 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.
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: seronday on June 08, 2018, 10:08:54 am
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.
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: Circlotron on June 08, 2018, 11:36:53 am
In "DG1022 Function/Arbitrary Waveform Generator Calibration Guide"
Where can we find this publication?
Title: Re: DG1022Z amplitude jumps slightly with frequency change
Post by: exe on June 08, 2018, 04:57:57 pm
Where can we find this publication?