Author Topic: waveform generator  (Read 11365 times)

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Oracle

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waveform generator
« on: March 23, 2013, 09:20:24 pm »
Hi,

I'm planning to buy a waveform generator, but i don't know how to make a comparison between brands: which specs should I consider?
 

Offline Rerouter

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Re: waveform generator
« Reply #1 on: March 23, 2013, 09:26:41 pm »
perhaps start off with how your planning to use the thing? frequencies? voltages? currents? waveform purity? any need for arbitrary waveforms? etc
 

Offline Ba1tuks

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Re: waveform generator
« Reply #2 on: March 23, 2013, 09:52:25 pm »
First of all, if you ask what gen to buy - you definitely don't need arbitrary one... Would be just a waste of money ;-)
 

Offline gearhead

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Re: waveform generator
« Reply #3 on: March 23, 2013, 10:14:31 pm »
Definitely depends on what you plan to use it for. I got a BK Precision 3011B, it's a 2mHz unit. Works good for general troubleshooting and I only gave $50 for it. The only thing I had to do was build a selectable attenuator so I could get the output voltage down to about 35mvpp. The lowest it would go into a 50ohm load was about 1.5volts pp.
« Last Edit: March 23, 2013, 10:16:39 pm by gearhead »
 

alm

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Re: waveform generator
« Reply #4 on: March 23, 2013, 10:20:29 pm »
I got a BK Precision 3011B, it's a 2mHz unit.

2 mHz is useless for electronics, those kind of frequencies might be of interest for mechanical or some biological work. Generators for electronics purposes should span at the very least the audio range, and preferably up to a few MHz.
 

Offline MacAttak

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Re: waveform generator
« Reply #5 on: March 24, 2013, 03:22:15 am »
Willing to bet he/she meant MHz and not mHz. But yeah, measurement units are important here and this particular one gets people frequently  :)
 

Oracle

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Re: waveform generator
« Reply #6 on: March 24, 2013, 09:36:00 am »
perhaps start off with how your planning to use the thing? frequencies? voltages? currents? waveform purity? any need for arbitrary waveforms? etc

I just need this one for general purpose 10 Mhz should be enough, 10Vpp current i don't care..

First of all, if you ask what gen to buy - you definitely don't need arbitrary one... Would be just a waste of money ;-)

well,  preferably i wish to have this option: i don't want to buy another one in future, so for me it's better to buy a good one now than have 2 generators: i don't have too much space left in my room...
 

Offline Gunb

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Re: waveform generator
« Reply #7 on: March 24, 2013, 09:52:03 am »
Hi,

I'm planning to buy a waveform generator, but i don't know how to make a comparison between brands: which specs should I consider?

Money?
 

Offline larry42

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Re: waveform generator
« Reply #8 on: March 24, 2013, 10:21:24 am »
If you have an animated GIF in your avatar or signature then I reserve the right to think you're a dolt.
 

Online nctnico

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Re: waveform generator
« Reply #9 on: March 24, 2013, 11:21:57 am »
perhaps start off with how your planning to use the thing? frequencies? voltages? currents? waveform purity? any need for arbitrary waveforms? etc

I just need this one for general purpose 10 Mhz should be enough, 10Vpp current i don't care..

First of all, if you ask what gen to buy - you definitely don't need arbitrary one... Would be just a waste of money ;-)

well,  preferably i wish to have this option: i don't want to buy another one in future, so for me it's better to buy a good one now than have 2 generators: i don't have too much space left in my room...
I recently bought a Siglent SDG1010 arb. generator. I have used it a couple of times and I'm pleased with it. The price is very reasonable.

I also have a big Lecroy arb. generator (but that is heavy and noisy) and an analog function generator but that one isn't precise so I always need a scope to check the output. I used to have a HP3314A function generator which is a very nifty piece of equipment but it was also heavy and noisy.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Oracle

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Re: waveform generator
« Reply #10 on: March 24, 2013, 12:42:27 pm »
Hi,

I'm planning to buy a waveform generator, but i don't know how to make a comparison between brands: which specs should I consider?

Money?

around $1000... max $2000 +/- $500
« Last Edit: March 24, 2013, 12:51:25 pm by Oracle »
 

Oracle

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Re: waveform generator
« Reply #11 on: March 24, 2013, 12:57:08 pm »
Here you are, OP, this should be enough based on your information:

http://www.home.agilent.com/en/pd-1809255-pn-81180B/46-gsa-s-arbitrary-waveform-generator?nid=-536902257.930158&cc=US&lc=eng

Next.

look: if only one option is about 50,000 EUR, how much is for the entire generator? about 100,000 EUR? No, it's actually more than my house value and I have to work more than 5 year in order to buy it  :)
 

Offline JuiceKing

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Re: waveform generator
« Reply #12 on: March 24, 2013, 01:17:13 pm »
Hi,

I'm planning to buy a waveform generator, but i don't know how to make a comparison between brands: which specs should I consider?

Money?

around $1000... max $2000 +/- $500

That's more than enough. I bought a used HP 33120A for a fraction of this and it's served me very well. Be aware that bandwidth is stated for sine wave output, and not square waves, which cannot be expected to be square at anything approaching the upper frequency limit; rise-time is an important specification here. Also, spectral impurity (THD) can be surprisingly high--even in the audio range--in cheaper units, so check that carefully if you plan to use this as a signal source for distortion testing. Also, look for floating output(s). I have one signal generator (with excellent performance within its specs) that ties to earth ground, and this certainly has limited its flexibility. My main beef with the 33120A is that without diving deep into configuration menus, you can't tell whether you are in Hi-Z or 50-ohm mode, and as a result it's all too easy to misread the output voltage display.
« Last Edit: March 24, 2013, 05:15:10 pm by JuiceKing »
 

Online nctnico

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Re: waveform generator
« Reply #13 on: March 24, 2013, 01:42:51 pm »
There are quite a few Tektronix AWG and AFG waveform generators on Ebay in that price range. Be sure to make a close comparison between the specs though. The Siglent arb. generator I bought cost me €280 (including shipping) but it's specs are very close to the Tektronix devices except for jitter. So you have to ask yourself whether 8ns of jitter is worth $1000.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Oracle

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Re: waveform generator
« Reply #14 on: March 24, 2013, 02:15:11 pm »

That's more than enough. I bought a used HP 33120A for a fraction of this and it's served me very well. Be aware that bandwidth is stated for sine wave output, and not square waves, which cannot be expected to be square at anything approaching the upper frequency limit; rise-time is an important specification here. Also, spectral purity (THD) can be surprisingly high--even in the audio range--in cheaper units, so check that carefully if you plan to use this as a signal source for distortion testing. Also, look for floating output(s). I have one signal generator (with excellent performance within its specs) that ties to earth ground, and this certainly has limited its flexibility. My main beef with the 33120A is that without diving deep into configuration menus, you can't tell whether you are in Hi-Z or 50-ohm mode, and as a result it's all too easy to misread the output voltage display.


Hmm, yes, maybe i should consider also the THD.... it's not banal as i thought thanks.  :)

I also see some HP 33120A one ebay, and i also see they are cheaper than the "new" agilent model: the 33210A.. 
 

Oracle

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Re: waveform generator
« Reply #15 on: March 24, 2013, 02:17:12 pm »
There are quite a few Tektronix AWG and AFG waveform generators on Ebay in that price range. Be sure to make a close comparison between the specs though. The Siglent arb. generator I bought cost me €280 (including shipping) but it's specs are very close to the Tektronix devices except for jitter. So you have to ask yourself whether 8ns of jitter is worth $1000.

no, a 8ns jitter don't worth $1000 (for me of course)
 

alm

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Re: waveform generator
« Reply #16 on: March 24, 2013, 02:31:28 pm »
There are quite a few Tektronix AWG and AFG waveform generators on Ebay in that price range. Be sure to make a close comparison between the specs though. The Siglent arb. generator I bought cost me €280 (including shipping) but it's specs are very close to the Tektronix devices except for jitter. So you have to ask yourself whether 8ns of jitter is worth $1000.
There's more than specs. There's also reliability, documentation, support, user interface design and general quality. Are the instruments barely meeting the specs at the moment they leave the factory, or can you count on them still being comfortably in specs after ten years? Will the PC software still work if the next version of Windows is released? I haven't used the Siglent, so I'm not in a position to compare, but claiming they are identical apart from the jitter just based on datasheet specs is misleading.
 

Oracle

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Re: waveform generator
« Reply #17 on: March 24, 2013, 02:44:16 pm »
well, the next windows version is the last problem: you can virtualize a machine and you are ok. 
 

Online jpb

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Re: waveform generator
« Reply #18 on: March 24, 2013, 03:13:15 pm »
At the top end of your budget (I don't know whether your budget includes tax or not), but you may be interested in :

http://www.ebay.co.uk/itm/Agilent-33522A-Function-Arbitrary-Waveform-Generator-30-MHz-/181101011040?pt=LH_DefaultDomain_0&hash=item2a2a762060

I've been eying it up as I'm in the market to get an AWG/AFG but its rather over my budget range. Be aware it is not a certiprime one so doesn't carry a long warranty and also Agilent stopped selling this model in March this year. The price they are asking is about 55% of new and it has nice specs.
 

Oracle

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Re: waveform generator
« Reply #19 on: March 24, 2013, 03:32:53 pm »
yes, this is a very nice gen, great THD and bandwidth, but is vat not included, so definitely is more than my budget....
 

Online nctnico

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Re: waveform generator
« Reply #20 on: March 24, 2013, 04:14:15 pm »
There are quite a few Tektronix AWG and AFG waveform generators on Ebay in that price range. Be sure to make a close comparison between the specs though. The Siglent arb. generator I bought cost me €280 (including shipping) but it's specs are very close to the Tektronix devices except for jitter. So you have to ask yourself whether 8ns of jitter is worth $1000.
There's more than specs. There's also reliability, documentation, support, user interface design and general quality. Are the instruments barely meeting the specs at the moment they leave the factory, or can you count on them still being comfortably in specs after ten years?
Nowadays most equipment is fully digital with a tiny bit of analog so aging will have very little effect. Besides the Siglent is so cheap that by the time it gets quirky I simply buy a new and much better one and still spend less money than buying a Tek or Agilent which will be outdated and unsupported by then as well.

Where it gets hairy is when you need equipment with traceable calibration. But that is only required if you do certification or calibration work where the paperwork needs to be in order to keep the pencil pushers happy. My primary use is for development where no paperwork is required.
Quote
Will the PC software still work if the next version of Windows is released?
You have the same problem with equipment from Tektronix, Agilent or Lecroy. I have several pieces of older equipment and the PC software won't work on Windows. Actually Lecroy sells the Siglent generators under their own brand. I'm using Lecroy's firmware on mine. I didn't try the software though. But there is always the possibility of using a virtual machine to run any version of Windows.
Quote
I haven't used the Siglent, so I'm not in a position to compare, but claiming they are identical apart from the jitter just based on datasheet specs is misleading.
What is misleading about comparing the specs and noting only the jitter performance is different? BTW the Tektronix AFG/AWG I compared has a sticker on the back saying it is made in China. What else do you expect from a function generator? If I buy a piece of equipment I expect it to work out of the box and not be dependant on the manufacturer to make it work somewhere in the future.
« Last Edit: March 24, 2013, 04:26:18 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online jpb

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Re: waveform generator
« Reply #21 on: March 24, 2013, 08:00:27 pm »
I've been going round in circles looking at AWGs and AFGs for several months, the main ones I've been looking at are the Rigol DG4062, the TTi TG5011, a Tabor WW5061 and the Agilent 33521Aequivalent. Pricewise the Rigol is the cheapest new but the others are available as ex-demo, old-stock, on e-bay for prices that are close to the Rigol (for instance a single channel Agilent 33521A went for £850 on e-bay recently, an ex-demo TTi TG5011 costs about the same as a Rigol DG4062 at around £700 but again it is only single channel).

One thing that strikes me about the cheaper Rigol is that

a) you get a lot of value for your money in terms of high frequency sine waves and the spec.

b) the high sample rate combined with the arb waveform option allows sine waves up to 150MHz even on the 60MHz model (there's a thread on this forum on it).

BUT

a.) the amplifier is low frequency so 10Vpp is only available to 20MHz

b.) the raw output (as from the arb option) shows quite a bit of slope which is compensated using "calibration" to get the specs for the built-in sine but
such calibration can't be done for arb wave forms (except by the user prescaling the waveform but this would only work at one frequency)

c.) the arb memory is only 16k and the sample rate is fixed at 500MS/s

The Agilent and Tabor have superficially the same or worse specs than the Rigol but have variable clock and the amplifiers and filters are intrinsically better so are not so reliant on calibration. They have much more memory (up to 16M on the Agilent) and it can be segmented and loops used to produce a lot more versatile output.

The Tabor and the TTi have calibration instructions in their manuals so the user can maintain them, if the Rigol drifts so the initial calibration is less effective then there is no easy way to correct it.

For standard waveforms the Rigol is a very good choice, it is very cheap for a two channel instrument, the tear downs show that it is well constructed and you can produce sines to a high frequency as long as you don't want to produce a 10Vpp sine wave above 20MHz - you can produce a 1Vpp one to 150MHz.

But if you want a lot of flexibility in arbitrary waveforms say to produce pulse streams with the occasional runt pulse or add a glitch to one in every million sine waves then something like the Agilent or the Tabor allows you to do that.

The TTi TG5011 is in-between. It has similar specs to the Rigol - it can't go to such high frequency on sine waves but its amplifier is good to 10Vpp up to the full 50MHz and it has closed box calibration which is easy to do. It only has 1 channel as well.

The Siglent is even cheaper than the Rigol and presumably is a good option for turning out standard waveforms but I suspect the Rigol is better built for this role.

Its horses for courses but I think the more expensive options (eg Agilent ) cost more for a reason other than just the brand name, but if you don't want high-fidelity large signals or flexible arbitrary waveforms then you're paying a lot more money for features you won't use.
 

alm

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Re: waveform generator
« Reply #22 on: March 24, 2013, 09:11:57 pm »
Nowadays most equipment is fully digital with a tiny bit of analog so aging will have very little effect. Besides the Siglent is so cheap that by the time it gets quirky I simply buy a new and much better one and still spend less money than buying a Tek or Agilent which will be outdated and unsupported by then as well.
A used Agilent 33120A, for example, comes with a service manual with full schematics. This service manual will still be usable ten years down the road. This manual also documents the communication protocol, allowing the user to easily write my own software to interface with it. I still use 20+ years old equipment this way, even though I don't have an antique computer that is able to run the software. PC software is essential for an AWG/AFG in my opinion, since I don't feel like entering the thousands/millions of points through the front panel.

You have the same problem with equipment from Tektronix, Agilent or Lecroy. I have several pieces of older equipment and the PC software won't work on Windows.
They will usually keep supporting their hardware for much longer. Rebadged stuff tends to be an exception, since they're often dependent on the OEM for software support. Agilent updated the Intuilink for the 33120A software a few years ago for Windows Vista, even though the function gen was designed in the late nineties and replaced early-mid 2000. I remember an incident of Rigol replacing the DG1022 by a new revision, and the software would only support the new hardware revision. No support at all for the earlier version of the instrument, and the software they had released was a piece of junk. Of course the instruments had the same type and part number, so no easy way to know which one you're ordering.

How is the Siglent software? Last time I tried the Rigol AFG software it was very basic, and their recommendation for more complex signals appeared to be to download Tektronix ArbExpress and import the signal in the Rigol software. Not exactly convenient.

What is misleading about comparing the specs and noting only the jitter performance is different? BTW the Tektronix AFG/AWG I compared has a sticker on the back saying it is made in China. What else do you expect from a function generator? If I buy a piece of equipment I expect it to work out of the box and not be dependant on the manufacturer to make it work somewhere in the future.
Claiming that the extra $1k only buys you less jitter is misleading. Whether documentation, support, probably quality (assuming they were in house designs) and brand name are worth the extra $1k to you is of course a different matter.
 

Offline Wuerstchenhund

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Re: waveform generator
« Reply #23 on: March 25, 2013, 10:44:03 am »
How is the Siglent software?

It's very basic, and not very reliable. No comparison with Agilents IntuiLink software for their AWGs.

BTW: LeCroy offers the same Siglent software for download for their SDG1000 rebadges (WaveStation), so no improvement there either.

Quote
Claiming that the extra $1k only buys you less jitter is misleading.

That's true, but at least in comparison with a Siglent SDG1000 it does buy you a lot less jitter.

Quote
Whether documentation, support, probably quality (assuming they were in house designs) and brand name are worth the extra $1k to you is of course a different matter.

The thing is that the Siglent SDG1000 is a toy, and while the general hardware quality seems to be ok the design is flawed (jitter issue). It may be cheap but considering that most modes suffer from terrible jitter it still is rather expensive.

Buying my SDG1020 was a mistake, and next time I'd rather buy a 20 year old HP/Tek/LeCroy/Philips/whatever big brand than any cheap Chinese-designed crap.
 

Offline rf-loop

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Re: waveform generator
« Reply #24 on: March 25, 2013, 12:01:37 pm »

The thing is that the Siglent SDG1000 is a toy, and while the general hardware quality seems to be ok the design is flawed (jitter issue). It may be cheap but considering that most modes suffer from terrible jitter it still is rather expensive.

What terrible jitter?

It is true that square have jitter due to how just square is produced. But also it is in specs. (0.1% and so on) It is becouse it is derived from sinewave using comparators. (this I do not know why but it is not only Siglent idea.)

If need less timing jitter there can use pulse mode for square wave and it have 8ns peak to peak not cumulative jitter. This is becouse 125MSa/s and there is not littlebit complex methods used for reduce jitter.

This machine works just as it principle is. This is well explained example in some Agilent app note.

This have normal jitter for this kind of equipment and jitter is also normal, not any special terrible if we keep looking this kind of equipments.

It is in my opinion good in its price class if look how it works and what all features it have if look modulations, sweeps, sync, etc.  Signal quality is not at all bad in its class.
Of course old middle and high-end or even state of art arb and other generators have lot of better specs. Also I have some these. But if somewhere is terrible jitter it is example HP8161A programmable pulse generator. If people need very low jitter it is good to know what need and do not buy example this Siglent. But also do not buy same class Rigol etc.  Of course also Siglent and Owon have lot of better models and more expensive also. Before buy it is good to understand what is buying. Example these jitter read in specs.  It is nice Siglent tell peak to peak jitter instead of rms jitter as many do for more nice looking numbers.

But yes. 8ns jitter is of course terrible.

If there is 10 second period 50% square wave (why hell use this mode if need less timing jitter - perhaps user do not know what he is doing)
there may  be (typical) 10ms random jitter... 10000000ns! jitter and itv reads in specs, it is designed so. Why user do not use pulse mode and go with around 8ns jitter (exept that with long times there come also system clock "walking" around and timing accuracy is reduced by this. Then can use external good freq reference. )

But then also some manufacturer tell jitter as rms. Some tell peak to peak. This may be big difference. If jitter time is gaussian random it may mean in practice near 10 times difference.
Example Agilent 33220A and square: Jitter (RMS) 1 ns + 100 ppm of period. Terrible or perfect?

How much is peak-peak jitter time in worst case.  1kHz square period time is 1000000ns. 100ppm is 100ns and +1 so specs tell that 101ns jitter RMS.  Siglent for Square: Jitter 0.1% of period with 1kHz (typical)  and it do not tell if this is peak-peak or RMS  but with my measurements it looks more like peak-peak.
For Arb Agilent  tell  Jitter (RMS) 6 ns + 30 ppm and agen RMS.   Siglent for Arb: peak-peak 8ns (typical).


Lets look this: http://www.sitime.com/support2/documents/AN10007-Jitter-and-measurement.pdf  for thinking about rms vs p-p.


Here some tiny tests (designed is more tests but just total lack of time)

http://siglent.freeforums.org/tests-siglent-sdg1000-function-arbitrary-waveform-generator-t5.html

This is for random hobby use and for professional use IF user need meet specs. This is NOT high end lab equipment. This is well under 0.5k$ "multifunction" apparatus. Building quality is also good in its class.

(in some old HW there can littlebit improve square wave quality by doing tiny modification as Siglent have told. (Comparators Hys setting resistors))






« Last Edit: March 29, 2013, 02:37:47 pm by rf-loop »
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Online nctnico

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Re: waveform generator
« Reply #25 on: March 25, 2013, 12:46:14 pm »
Nowadays most equipment is fully digital with a tiny bit of analog so aging will have very little effect. Besides the Siglent is so cheap that by the time it gets quirky I simply buy a new and much better one and still spend less money than buying a Tek or Agilent which will be outdated and unsupported by then as well.
A used Agilent 33120A, for example, comes with a service manual with full schematics. This service manual will still be usable ten years down the road. This manual also documents the communication protocol, allowing the user to easily write my own software to interface with it. I still use 20+ years old equipment this way, even though I don't have an antique computer that
The Siglent supports USBTMC so you don't need any Siglent specific drivers. The programming manual can be downloaded from Lecroy. You can also opt to use a USB-GPIB dongle from the front and connect it to a GPIB bus. So programming without Siglent's / Lecroy's software is no problem.

I've used the Agilent 33120A a long time ago but I never liked the user interface. If you buy an AFG/AWG make sure it has a big screen so you can see what you are doing.

@Wuerstchenhund: In what way does the jitter make it useless for you? I've used my Siglent SDG for several measurements (including pulses) but the jitter didn't got in the way. Actually I knew about the jitter before I bought it.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Oracle

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Re: waveform generator
« Reply #26 on: March 29, 2013, 01:41:00 pm »
@ jpb: ok, so a Rigol should fit my needs, the other choice would be an Agilent 332**A.... I don't know, I have to find out more time to read and compare the whole data sheet.

Big screen arbitrary are a problem: in my room there is no much space left... and i don't want to have a valuable portable instrument in the garage.
 


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