DG1022Z amplitude jumps slightly with frequency change - Page 1
Forum section: electronics / testgear

author: Circlotron
author_rank: Super Contributor
timestamp: May 25, 2018, 11:40:31 am
content: 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?

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 31, 2018, 10:13:57 am
content: I have a DG1022Z, how are you doing the measurement?

author: exe
author_rank: Unknown
timestamp: May 31, 2018, 11:11:17 am
content: 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?

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 31, 2018, 11:45:36 am
content: 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 outputdecreasedfrom 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.

author: Circlotron
author_rank: Super Contributor
timestamp: May 31, 2018, 12:01:24 pm
content: 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.

author: Circlotron
author_rank: Super Contributor
timestamp: May 31, 2018, 12:03:33 pm
content: Quote from: exe on May 31, 2018, 11:11:17 amVery very slightly higher than 100kHz

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: May 31, 2018, 12:13:50 pm
content: 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.

author: exe
author_rank: Unknown
timestamp: May 31, 2018, 12:33:46 pm
content: 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.

author: seronday
author_rank: Regular Contributor
timestamp: June 08, 2018, 10:08:54 am
content: 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.

author: Circlotron
author_rank: Super Contributor
timestamp: June 08, 2018, 11:36:53 am
content: Quote from: exe on May 31, 2018, 12:33:46 pmWhere can we find this publication?

author: exe
author_rank: Unknown
timestamp: June 08, 2018, 04:57:57 pm
content: Quote from: Circlotron on June 08, 2018, 11:36:53 amUhm, first link in google.

author: Circlotron
author_rank: Super Contributor
timestamp: June 08, 2018, 10:04:38 pm
content: When I looked (before I asked) it only referenced this thread. I’ll have to try again!

author: exe
author_rank: Unknown
timestamp: June 09, 2018, 11:20:46 am
content: Quote from: Circlotron on June 08, 2018, 10:04:38 pmJust in case, here is the link:https://www.eevblog.com/forum/testgear/rigol-dg1022-how-to-update-the-firmware/msg583501/#msg583501(or direct linkhttps://www.eevblog.com/forum/testgear/rigol-dg1022-how-to-update-the-firmware/?action=dlattach;attach=128726).

author: bd139
author_rank: Super Contributor
timestamp: June 09, 2018, 12:25:38 pm
content: 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.