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Author Topic: Rigol signal generator owners, please help  (Read 2323 times)

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Offline MichalPL

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Rigol signal generator owners, please help
« on: April 18, 2017, 10:48:47 AM »
Hi, I've recently bought the GW Instek AFG-2225 signal generator but I'm dissatisfied with the fact the despite the promised 25 MHz square, for anything above 10-11 MHz or so the 'square' turns into a 'sine wave'. Yes, I'm measuring it using the feed-through 50 Ohm terminator on a 200 MHz scope. I believe this is because the rise time is quite high, 25 ns. The other generator that I considered is one of the Rigols and before I dump this one I have to be sure that a Rigol can meet my needs. Especially given the fact that it's hard to compare the specs and it may turn out that the general signal distortion at reasonable amplitudes is lower on the Instek than on Rigols.

Anyway, what I'd like to kindly ask you is to show me what a 20 or 25 MHz square wave looks like when watched on a 100+ MHz scope, when using a 50 Ohm terminator or the HighZ output option, at 3Vpp or more. Whether it truly is a square or maybe it also looks like a sine. The models that I'm interested in are: DG1022Z, DG1022A or DG1032Z.

And if by chance you also have some comparison between the Instek's and Rigol's AWG software for Win, please share your thoughts. Thanks!
« Last Edit: April 18, 2017, 11:03:25 AM by MichalPL »
 

Offline xrunner

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Re: Rigol signal generator owners, please help
« Reply #1 on: April 18, 2017, 10:56:45 AM »
Well I have a DG1032Z, but if I can get my cat off of my lap and get to my bench before someone else does it I'll do it tonight. Well even if someone else does I will anyway.  8)
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline MichalPL

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Re: Rigol signal generator owners, please help
« Reply #2 on: April 18, 2017, 11:01:19 AM »
Highly appreciated. Say my hello to your cat :)
 

Online tautech

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Re: Rigol signal generator owners, please help
« Reply #3 on: April 18, 2017, 11:06:28 AM »
Check out this thread for the squarewave performance of many AWG's:
http://www.eevblog.com/forum/testgear/show-us-your-square-wave/
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Offline xrunner

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Re: Rigol signal generator owners, please help
« Reply #4 on: April 18, 2017, 11:09:09 AM »
Well it didn't take that long.

The DG1032Z will only generate a square wave up to 15 MHz. But this is it into a 50 ohm load at the scope input.
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline hexreader

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Re: Rigol signal generator owners, please help
« Reply #5 on: April 18, 2017, 11:32:07 AM »
Rigol DG 2041A 5Vpp square wave into 50 Ohm terminator and Rigol MSO1104Z (100MHz scope)

Top to bottom:    20MHz, 25MHz, 40MHz
 

Offline hexreader

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Re: Rigol signal generator owners, please help
« Reply #6 on: April 18, 2017, 11:49:17 AM »
And same setup for GW Instek AFG-2105 (only goes up to 5MHz  :-[ )

Rise time seems a lot slower, but maybe the newer models are better?

My experience of software is that GW Instek is poor (but at least it works), but Rigol software is truly terrible to the point of unusable (as it only work occasionally and even then not for long before crashing). Win 10 64 bit.

DOH - wrong attachment - will try again - done

 

Online Tom45

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Re: Rigol signal generator owners, please help
« Reply #7 on: April 18, 2017, 01:27:13 PM »
Well it didn't take that long.

The DG1032Z will only generate a square wave up to 15 MHz. But this is it into a 50 ohm load at the scope input.

You must have an older DG1032Z like I do. The current specs for the DG1032Z say 25 MHz for square waves. Strange.

Here's what I get for 10 and 15 MHz fed into a Tek 7A24 plugin with 50 ohm inputs:





 

Offline Mechatrommer

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Re: Rigol signal generator owners, please help
« Reply #8 on: April 18, 2017, 04:18:02 PM »
ad9850 module 1vpp square output through 50ohm feedthrough...
10MHz and 25MHz
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline tech5940

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Re: Rigol signal generator owners, please help
« Reply #9 on: April 18, 2017, 07:22:50 PM »
Well it didn't take that long.

The DG1032Z will only generate a square wave up to 15 MHz. But this is it into a 50 ohm load at the scope input.

You must have an older DG1032Z like I do. The current specs for the DG1032Z say 25 MHz for square waves. Strange.

Here's what I get for 10 and 15 MHz fed into a Tek 7A24 plugin with 50 ohm inputs:



I think the latest firmware update for the DG1000Z series had a note about increasing the square wave output to 25Mhz.
 

Offline David Hess

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Re: Rigol signal generator owners, please help
« Reply #10 on: April 18, 2017, 11:11:52 PM »
Function generators have to use linear output stages to preserve sine and triangle fidelity so their main output is not ideal for generating sharp square waves.  Imagine trying to push a square wave through a limited bandwidth feedback amplifier.

An easy solution is to use the function generator's sync output which produces logic levels but unfortunately the GW Instek AFG-2225 and most modern function generators lack this.  If more flexibility is required, then a dedicated pulse generator can be used.
 

Offline simone.pignatti

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Re: Rigol signal generator owners, please help
« Reply #11 on: April 19, 2017, 12:09:30 AM »
Hi, I've recently bought the GW Instek AFG-2225 signal generator but I'm dissatisfied with the fact the despite the promised 25 MHz square, for anything above 10-11 MHz or so the 'square' turns into a 'sine wave'. Yes, I'm measuring it using the feed-through 50 Ohm terminator on a 200 MHz scope. I believe this is because the rise time is quite high, 25 ns. The other generator that I considered is one of the Rigols and before I dump this one I have to be sure that a Rigol can meet my needs. Especially given the fact that it's hard to compare the specs and it may turn out that the general signal distortion at reasonable amplitudes is lower on the Instek than on Rigols.

Anyway, what I'd like to kindly ask you is to show me what a 20 or 25 MHz square wave looks like when watched on a 100+ MHz scope, when using a 50 Ohm terminator or the HighZ output option, at 3Vpp or more. Whether it truly is a square or maybe it also looks like a sine. The models that I'm interested in are: DG1022Z, DG1022A or DG1032Z.

And if by chance you also have some comparison between the Instek's and Rigol's AWG software for Win, please share your thoughts. Thanks!

I'm looking at the brochure and it is strange they state "Wide Frequency Ranges From 1uHz - 25MHz {sine wave}"

http://www.gwinstek.com/en-global/Download/DownloadFile/DownloadFile/download%23_%2303_Signal%23_%23AFG%23_%23AFG-2225_BH_E.pdf

Then when you scroll down you will see the same specs for sine and square.

We have done a video on the DG1022Z you can see here



However no square wave there, I will work on it later today and post here some results.
Bye
« Last Edit: April 19, 2017, 12:12:25 AM by simone.pignatti »
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Offline xrunner

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Re: Rigol signal generator owners, please help
« Reply #12 on: April 19, 2017, 12:40:17 AM »
I think the latest firmware update for the DG1000Z series had a note about increasing the square wave output to 25Mhz.

Yea OK thanks I just got the latest firmware (00.01.12) and it does allow one to select square waves up to 25 MHz. But past 20 MHz they get really sine-wavy ...
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Online Tom45

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Re: Rigol signal generator owners, please help
« Reply #13 on: April 19, 2017, 12:46:11 AM »
Thanks for pointing that out.  I found that an update last September did increase the limit for square waves to 25 MHz.

This shows 15 MHz, 25 MHz, and the sync output from 25 MHz. As David pointed out, the sync output is of far better quality. For generators that don't have a sync output running the signal through a schmitt trigger would accomplish about the same thing. But there is no flexibility for amplitude and offset with either the sync output or the schmitt trigger.


 

Offline simone.pignatti

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Re: Rigol signal generator owners, please help
« Reply #14 on: April 19, 2017, 01:08:27 AM »
Oscilloscope RIGOL MSO4054
Generator RIGOL DG1062Z
frequencies steps: 500kHz, 1MHz, 5MHz, 10MHz, 15MHz, 20MHz, 25MHz













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Offline David Hess

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Re: Rigol signal generator owners, please help
« Reply #15 on: April 19, 2017, 01:38:11 PM »
As David pointed out, the sync output is of far better quality. For generators that don't have a sync output running the signal through a schmitt trigger would accomplish about the same thing. But there is no flexibility for amplitude and offset with either the sync output or the schmitt trigger.

My old B&K function generator has two switch selected modes for the sync output.  One produces a TTL output but the other uses a CMOS analog multiplexer to generate an adjustable 0 to 15 volt output for driving high voltage CMOS.  Back before I had a reference level pulse generator, I modified the TTL output for roughly the same capability using a 74AS140.

In principle there is no reason the sync output cannot be fast with adjustable levels and many pulse generator main outputs operate this way but it would be an odd capability for a function generator sync output which is intended for driving a trigger input on some other instrument.

Incidentally, really good function generators with a sync output include common mode isolation between the sync and function outputs to prevent the sync output signal from showing up as a glitch in the function output.
 

Offline MichalPL

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Re: Rigol signal generator owners, please help
« Reply #16 on: April 19, 2017, 10:06:52 PM »
Thank you all. After what I saw, I've decided to return the Instek and go for Rigol DG1032Z.
One more question, though. Recently I've been thinking of playing with making some audio pre- and amplifiers. I know it's a long way to go before I'll be able to call it high-end audio, however I already wonder if such a general purpose signal generator will do for some time, or if I should rather look for a one specific to audio applications from the start. I know there's some old Tek model widely praised on the forum, yet its availability is limited and hence I wonder if something like this is worth something and would give me some significant gain over the Rigol for audio purposes: http://www.gwinstek.com/en-global/products/Signal_Sources/Other_Signal_Sources/GAG-810_GAG-809
 

Offline David Hess

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Re: Rigol signal generator owners, please help
« Reply #17 on: April 20, 2017, 03:08:14 AM »
For all audio applications except for the most basic, you will need something with lower distortion than a function generator, even a modern one, will provide.

There is a lot of demand for low distortion signal generators so the Tektronix SG502 commands a high price.  HP made many low distortion oscillators as well.

What would be more useful though is a good sound card or audio interface for your PC and some software for doing spectrum analysis.  The only difficulty with this is avoiding common mode problems.

 

Offline MichalPL

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Re: Rigol signal generator owners, please help
« Reply #18 on: April 20, 2017, 08:12:44 AM »
Hi David, but don't such old analyzers loose their parameters due to aging, drying of capacitors, etc.?
Is it really better to buy a 20yo Tec or maybe something of worse specs but brand new?
 

Offline David Hess

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Re: Rigol signal generator owners, please help
« Reply #19 on: April 20, 2017, 10:20:45 AM »
Hi David, but don't such old analyzers loose their parameters due to aging, drying of capacitors, etc.?
Is it really better to buy a 20yo Tec or maybe something of worse specs but brand new?

Oscillators like the old low distortion Tektronix SG502 and HP oscillators will need some maintenance like replacing power supply capacitors but since they are fully documented, that is easy to do.  Of course you still need something to measure the results; the FFT function on your oscilloscope will only be suitable for high levels of distortion but maybe that is enough.

The problem is finding something new at a hobby price with not terrible specifications for audio circuit design.  It is too specialized of a field for the cheap equipment manufacturers like Rigol to get involved.  The closest new suitable audio source is the audio output from a good sound card or audio DAC which is why I suggested it and ultimately using a PC as an audio analyzer will save a lot of time anyway.

Check out True Audio's software and their recommended hardware:

https://trueaudio.com/index.htm

Also check out QuantAsylum:

https://quantasylum.com/

Picoscope has some products but if you can pay their prices, then you do not need advice.
 
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