AWG Sig Gen - Agonising over choice! Rigol/Agilent/Siglent (huh???)

[saturation]

Hi LaurenceW,

Its a matter of your intent for your gear.  If you are using gear mostly to design, high fidelity is more important than convenience.  DDS is famous for stability but higher distortion, analog generators give low distortion, but more prone to frequency drift.  arbs need to be specified by the number of bit resolution, to improve its resolution and reduce distortion.  If the arb need is fairly low or uncertain, used pulse generators, etc., from eBay sell for far less than a new Rigol, and made by more reputable makers.  If you choose one from 1990s technology they are fairly easy to repair and, likely, made of parts from the golden days of USA, Japan, EU and Taiwan sources with far better quality than today.

There is strong suggestion than cheapo arb or DDS generators can produce high quality and spending more won't get you more, it depends on manufacturer [ see a thread on eevblog on the Velleman USB signal generator versus Hantek 3x25 regarding harmonic distortion content of its sine wave output.]  So you can get such a device separately, and get a separate pulse and function generator, all geared to be as best bang for buck, over say the Rigol.

I recent got this reference pulse generator capable of < 70ps for $70.  You can build the Jim Williams version for about the same money, but its designed only to go to 300ps-1ns range.

http://webpages.charter.net/dawill/tmoranwms/Elec_Pulse.html


As Bored suggests, I am too am very leery about buying from alibaba and most large China based vendors; if I do I would consider the purchase a complete gamble and know before hand I will lose all my money, or receive damaged goods. 

Alibaba is a strange name for a web business, he was in league with the '40 thieves.'  The story goes " ...popular perception of Ali Baba, and the way he is treated in popular media, sometimes implies that he was the leader of the "Forty Thieves": in the story he is actually an "honest man"[1] whom fortune enables to take advantage of the thieves' robberies."

http://en.wikipedia.org/wiki/Ali_Baba


So maybe the website is trying to make an honest living by hosting thieves?

I think it safer to buy direct from eBay based Chinese vendors as the 'small guy' is less likely to screw you given he wants business, and you can more easily chat with them via email to determine how honest they will deal with you.  eBay also tracks their history of successful transactions and, being based in the USA, you have some redress for complaints.

 

Saturation, that TEK looks like a nice piece of kit, almost tempted to add one to the list "for old times' sake"

I am looking for something which will see me right for maybe another ten years (then who knows what kit will be available??) without costing the earth.  I guess i know what my needs are NOW, but not what they might be in a few years!  The Rigol is looking like fitting the bill - as i currently see it.

....But Wait! What's this Rigol DG4062 for under 500 bucks:

http://www.aliexpress.com/product-gs/519276071-adopting-the-DDS-technology-two-channels-a-multifunctional-generator-DG4062-free-shipping-wholesalers.html

ohoh! Scope creep setting in....

[alm]

Its a matter of your intent for your gear.  If you are using gear mostly to design, high fidelity is more important than convenience.  DDS is famous for stability but higher distortion, analog generators give low distortion, but more prone to frequency drift.

Analog function generators suck as far as distortion of their sine output is concerned. The sine is usually generated by shaping a triangle wave until it looks approximately like a sine, a good one might do < 0.5% THD on a good day. A good DDS generator will be an order of magnitude better. There's a reason why the big brands like Agilent make (almost?) no analog function generators anymore.

[hazzer]

I bought the Siglent SDG 1020 back in Oct 2011....

I choice it over Atten range as the Siglent range has 14bit vertical resolution vrs the 8bit resolution of the Atten.
I though the Rigol were just a tad too expensive for my needs.
I'm very happy with the Siglent - the PC software is a bit clunky but it does do all its supposed to do.
(it runs on windows7 64bit as well)....

It comes with a useful range of pre loaded arbitrary waveforms ... so all in all I think it was good value.
Build quality is good - nice solid construction.

If you want any more info lets know.

Harry

[wkb]

I'm very happy with the Siglent - the PC software is a bit clunky but it does do all its supposed to do.
(it runs on windows7 64bit as well)....

As a matter of curiosity: does anyone know if there are vendors of AWG that have software that runs on MacOSX?  [I can dream, can I?]

[Bored@Work]

As a matter of curiosity: does anyone know if there are vendors of AWG that have software that runs on MacOSX?  [I can dream, can I?]

Your best bet would be an AWG that uses a well standardized USB class for communication, one by default implemented on the Mac, and where the vendor has properly documented the commands to be exchanged over USB. Alternatively, instead of USB a device supporting the LXI LAN interface, again with good documentation from the vendor.

Then "all" you need is a programmer writing some interface software and an AWG editor for you.

Interestingly, there is no real free / open source alternative for LabView, and there are only proprietary ,but no free implementations of VISA, LXI, IVI drivers etc. for Linux, Unix, Mac and the like. There are only fragments. A driver here, a GPIB library there, some VXI-11 tools, etc. But not a consistent, standardized (or setting the defacto standard) instrumentation framework.

If someone wants to make a name for himself in open source, here is the niche that is waiting to be filled.

[wkb]

As a matter of curiosity: does anyone know if there are vendors of AWG that have software that runs on MacOSX?  [I can dream, can I?]

Your best bet would be an AWG that uses a well standardized USB class for communication, one by default implemented on the Mac, and where the vendor has properly documented the commands to be exchanged over USB. Alternatively, instead of USB a device supporting the LXI LAN interface, again with good documentation from the vendor.

Then "all" you need is a programmer writing some interface software and an AWG editor for you.

Interestingly, there is no real free / open source alternative for LabView, and there are only proprietary ,but no free implementations of VISA, LXI, IVI drivers etc. for Linux, Unix, Mac and the like. There are only fragments. A driver here, a GPIB library there, some VXI-11 tools, etc. But not a consistent, standardized (or setting the defacto standard) instrumentation framework.

If someone wants to make a name for himself in open source, here is the niche that is waiting to be filled.

Thank you.  Done quite a bit of programming in the past, but writing something like this is more than a small time sink...  It is more a black hole of a time sink 

One would indeed like a FOS version of LabView, in a similar fashion like SciLab offers a FOS MathLab-like clone.

[Bored@Work]

Thank you.  Done quite a bit of programming in the past, but writing something like this is more than a small time sink...  It is more a black hole of a time sink 

Sure it is. I am always surprised that people do start large open source projects, knowing in advance that it will take them ages.

One would indeed like a FOS version of LabView, in a similar fashion like SciLab offers a FOS MathLab-like clone.

I think the biggest issue would be to get access to all the instruments for testing protocol and driver implementations. You can't afford to buy all those instruments. Even renting them for a short time would be insanely expensive. So you have to do such a project with the help of some company, university, research facility or the like, where they have a access to a lot of instruments. A fearless student might be the right one to get such a project started.

[alm]

Your best bet would be an AWG that uses a well standardized USB class for communication, one by default implemented on the Mac, and where the vendor has properly documented the commands to be exchanged over USB. Alternatively, instead of USB a device supporting the LXI LAN interface, again with good documentation from the vendor.

Is there an USBTMC driver for Mac? Even though this is a horrible standard, it is kind of a standard for interfacing T&M equipment via USB. RS-232 would be another option, assuming the protocol is documented.

Then "all" you need is a programmer writing some interface software and an AWG editor for you.

Or you could do like Rigol and use free Agilent/Tektronix software to generate the signals and import them in your program.

Interestingly, there is no real free / open source alternative for LabView, and there are only proprietary ,but no free implementations of VISA, LXI, IVI drivers etc. for Linux, Unix, Mac and the like. There are only fragments. A driver here, a GPIB library there, some VXI-11 tools, etc. But not a consistent, standardized (or setting the defacto standard) instrumentation framework.

There are some incomplete attempts like pylt, but nothing mature. I wouldn't be aiming for a Labview equivalent, just a standardized framework like VISA and bindings for popular programming languages.

I think the biggest issue would be to get access to all the instruments for testing protocol and driver implementations. You can't afford to buy all those instruments. Even renting them for a short time would be insanely expensive. So you have to do such a project with the help of some company, university, research facility or the like, where they have a access to a lot of instruments. A fearless student might be the right one to get such a project started.

You don't have to support everything. As long as you support the common interfaces (eg. USBTMC, RS-232, LXI, GPIB) and most types of instruments (eg. function gen, AWG, scope, DMM, counter, power supply), and make it easy to write instrument drivers, interested users can do the rest. Assuming the programming protocol was documented by the manufacturer. Those cheap disposable instruments without any documentation will always be an issue unless someone is motivated enough to reverse-engineer the protocol.

[saturation]

We don't see much of this brand here on eevblog, would be good if you could review it and place it on a separate thread if you can.

I bought the Siglent SDG 1020 back in Oct 2011....

I choice it over Atten range as the Siglent range has 14bit vertical resolution vrs the 8bit resolution of the Atten.
I though the Rigol were just a tad too expensive for my needs.
I'm very happy with the Siglent - the PC software is a bit clunky but it does do all its supposed to do.
(it runs on windows7 64bit as well)....

It comes with a useful range of pre loaded arbitrary waveforms ... so all in all I think it was good value.
Build quality is good - nice solid construction.

If you want any more info lets know.

Harry

[saturation]

Yes, concur but I was thinking of dedicated audio generators, so my bad.  The generic analog function generator is both distortion rich and unstable compared to most DDS based FG.

In the audio domain for example, you can eBay this old model for < $200, still sold, with sine wave distortion 0.004%, or~  -88dB

http://www.tequipment.net/KenwoodAG-253.html

Compared to a reference DDS based audio generator at - 100dB THD

http://www.thinksrs.com/products/DS360.htm

List price of $2800.

Its a matter of your intent for your gear.  If you are using gear mostly to design, high fidelity is more important than convenience.  DDS is famous for stability but higher distortion, analog generators give low distortion, but more prone to frequency drift.

Analog function generators suck as far as distortion of their sine output is concerned. The sine is usually generated by shaping a triangle wave until it looks approximately like a sine, a good one might do < 0.5% THD on a good day. A good DDS generator will be an order of magnitude better. There's a reason why the big brands like Agilent make (almost?) no analog function generators anymore.

[wkb]

Thank you.  Done quite a bit of programming in the past, but writing something like this is more than a small time sink...  It is more a black hole of a time sink 

Sure it is. I am always surprised that people do start large open source projects, knowing in advance that it will take them ages.

Hehe...    Been there, or rather, still am there.  Check out http://www.freebsd.org for my time sink of the last decade or so.

[grenert]

I bought the Siglent SDG 1020 back in Oct 2011....

I choice it over Atten range as the Siglent range has 14bit vertical resolution vrs the 8bit resolution of the Atten.

I'm surprised by the Siglent's sine wave distortion numbers in the audio spectrum (from the manual):
Total harmonic waveform distortion DC ~ 20 kHz?1 Vpp <0.2%

Those are rather high for a 14 bit DAC.  The old HP 33120A (12 bits) is specified to:
DC to 20 kHz <0.04%

Maybe in practice the Siglent performance is actually much better than specified.