Unlocking Siglent SDS1104X-E, step by step

[Fungus]

You only need 4 points to reproduce a perfect square wave.

With graph paper, sure, but not with sin(x)/x signal reconstruction. For anything resembling a square wave you need to see at least the first two harmonics so you need more than 12 sample points per wave.

(5 x 2.5 = 12.5)

[BillyO]

I was just pointing out the theoretical requirement.

Anyhow.  Below, the green trace is a (not terribly good) 100MHz square wave on a 600MHz scope and the same square wave in purple on an SDS1104X-E improved to 200MHz.  You can still very much see it's a (not terribly good) square wave.  On a 100MHz version it would not look nearly as square if at all..

[tautech]

What's this AC triggering BS Bill ? 

[BillyO]

What's this AC triggering BS Bill ? 

It was set up for something else.  I just quickly plugged the oscillator in and changed the time base.  That's what I saw, so didn't do any more.  Lazy..

[tautech]

Sometimes it's just easier to hit Default ......or if you have it set up a User Default. 

[Fungus]

You can still very much see it's a (not terribly good) square wave.

It's exactly what I would expect to see - a sine wave plus an attenuated sine wave at 3x the frequency.

But in this case it has nothing to do with not having enough samples. It's lack of bandwidth in the in the front end - they're not letting the 300MHz/500Mhz/700Mhz components of the "square wave" through.

On a 100MHz version it would not look nearly as square if at all..

On a 100MHz device the sine wave at 300Mhz wave will be more attenuated so it will closer to a pure sine wave.

[Deso]

That's got nothing to do with the lack of points.

A 100MHz "square wave" is made of a 100MHz sine wave + a 300MHz sine wave + a 500Mhz sine wave + ... etc.

Your oscilloscope can't see the 300Mhz wave or any of the other higher frequencies, all you can see is the 100MHz sine wave.

It's a good day for me to learn something new. Thanks.

So in the end the hack will only increase BW of forntend? Although I couldn't find anything from the pictures of frontend (HW 05) that might limit the BW.

[BillyO]

So in the end the hack will only increase BW of forntend? Although I couldn't find anything from the pictures of frontend (HW 05) that might limit the BW.

It's a feature of the modern Variable Gain Amplifiers (VGA) used in the front end.  Basically they have not only programable gain, but programable bandwidth too.

[Deso]

According to the pictures of SDS1104X-E, the AD8370 is used in HW 05. This VGA has no BW limiting capability (or I'm missing that feature in the datasheet).

[BillyO]

But in this case it has nothing to do with not having enough samples. It's lack of bandwidth in the in the front end - they're not letting the 300MHz/500Mhz/700Mhz components of the "square wave" through.

That's what I was trying to point out too, but I thought I'd do it with pictures.

The bottom line is there is definite benefit to the higher BW, even if the sample rate is not increased as well.

[BillyO]

According to the pictures of SDS1104X-E, the AD8370 is used in HW 05. This VGA has no BW limiting capability (or I'm missing that feature in the datasheet).

That's a pretty fast amplifier, but you're right, it does not have that function.

I honestly don't know where they are doing it.  It may even be a digital filter.  These scopes also have a 20MHz BW limit.  It may be done the same way as that.

All that said, the BW increase to 200MHz is real.

[robert.rozee]

my own take on it is that the only difference between 100MHz and 200MHz versions is that the 100MHz version has artificial software filtering to give the appearance of limited front-end bandwidth. the end result is that the 200MHz version acts more 'naturally' (like a CRO would) as input frequency increases, whereas the 100MHz version behaves in what feels like a disconcertingly 'odd' way.

bear in mind that i mostly look at digital signals, and ones at rates that are nowhere close to the 100MHz area. however, there are sharp edges. with my scope (SDS1104X-E) unlocked be to the 200MHz version the sorts of things i see on screen are significantly closer to what i expect. as a result, my opinion is that while i understand Siglent's motivation to create a product differentiation, the the software filtering used to create the 100MHz version does a disservice to the 100MHz product.


cheers,
rob   :-)

[Fungus]

So in the end the hack will only increase BW of forntend?

Yes.

[Fungus]

The bottom line is there is definite benefit to the higher BW, even if the sample rate is not increased as well.

Yes... until you start to turn on more channels and the sample rate halves. When that happens you'll be letting through more frequencies than can alias.

[robert.rozee]

So in the end the hack will only increase BW of forntend?

Yes.

No. so it seems we may disagree   

to get this straight:

1. my understanding is that the 100MHz version of the SDS1104X-E uses software filtering to give the appearance of limited front-end bandwidth. electrically the 100MHz and 200MHz versions of the scope have identical electrical signal paths, the filter is all done via a (digital) software algorithm in either the processor or FPGA.

2. your understanding is that the 100MHz version of the SDS1104X-E has the real bandwidth of the front-end limited via something like an electronic switch that turns on an actual physical filtering component in the front-end circuit path. hence the signal presented to the ADCs have followed through a (subtly) different electrical path.

do we have evidence to support theory 2. over theory 1.?


cheers,
rob   :-)

[Fungus]

do we have evidence to support theory 2. over theory 1.?

I dunno about Siglents but that's how some Rigols do it - they switch in extra capacitors on the front end to reduce the bandwidth.

[tautech]

So in the end the hack will only increase BW of forntend?

Yes.

No. so it seems we may disagree   

to get this straight:

1. my understanding is that the 100MHz version of the SDS1104X-E uses software filtering to give the appearance of limited front-end bandwidth. electrically the 100MHz and 200MHz versions of the scope have identical electrical signal paths, the filter is all done via a (digital) software algorithm in either the processor or FPGA.

2. your understanding is that the 100MHz version of the SDS1104X-E has the real bandwidth of the front-end limited via something like an electronic switch that turns on an actual physical filtering component in the front-end circuit path. hence the signal presented to the ADCs have followed through a (subtly) different electrical path.

do we have evidence to support theory 2. over theory 1.?
cheers,
rob   :-)

All 1000X-E models are a 200 MHz design SW limited to the various models in this range, in the west we see only 100 and 200 MHz models whereas in the east there is a 70 MHz model too !

Typically the IC that provides the 20 MHz BW filter can also provide the full BW limiter and for all the BW tests I've done on Siglent DSO's 5-20% over rated BW is typical however some models are substantially more, Eg the 500 MHz design 100 MHz SDS2104X Plus has -3dB BW of some 185 MHz and therefore supplied with 200 MHz probes.

Dave Jones has a good look at the VGA (variable gain amp) in a SDS114X-E in this vid from a few years back:
https://www.eevblog.com/2019/07/10/eevblog-1228-do-digital-scopes-have-real-verniers/

[pope]

I only do analog audio and I was wondering whether there's any benefit in unlocking this o'scope. I'm talking about the 200MHz unlock. I don't care about the other unlocking options. 

According to fungus, it might be even better to keep the scope at 100MHz due to aliasing (?). Unless I totally misinterpreting his post.

[nikitasius]

Hi, it work great, thanks !

I used SCPI to pass on 200MHz. For options it doesn't worked (while web UI told success), so i entered it manually.
And after unlocking all i restarted the scope & updated the firmware.

It's an awesome scope ❤️

Congrats.

When using the webserver SCPI command page to add options, the command syntax need be perfect.
Certainly it will report command sent successfully however unless the syntax is perfect it will not be accepted by the scope.
Enjoy.

Thanks i really do! Just wait from dealer new probe (cause one have internal contact issues), they will put it into generator box.

[nikitasius]

I don't get this hype regarding bandwidth hacking on sds1104x-e. At the end this is 1GSPS scope. Signals looks good up to 50Mhz and above that it's a bit of a stretch of the imagination. At 100Mhz there is only 10 points to reconstruct the signal (square wave looks like sine). At 200Mhz they are 5..

To not be completely off-topic - The changes between OS V2 and OS V3 is a one simple number (1 byte). In the

Code: [Select]

/etc/version file there is "rootfs_version=" with value 3 for OS v2 and value 4 for OS v3.
So anyone can change their OS to v3 without OS flashing.

Hi. I personally think that every job must be paid. Also i think that people need to respect the rules & obligations.

For me i got not a "wow i see 200MHz waves", but the perfect (i hope so) display all signals upto 100MHz i paid for. The features: i don't plan to use MSO nor WIFI nor the siglent's AWG.
I wanna buy better probes, yes (while existing are perfect for me cause it's mostly for audio freqs).

So with the hack i did Siglent company lost nothing, but got a good client. I got correct measures upto 100MHz (even bit more).

The AWG i paid is 16bit rigol DG811 (which will be hacked for max sampling).
I follow Dave's idea that beginners don't need overkills.

If after some time i see that i need "better" AWG or another features, i will buy another AWG w/ features i need or an another scope/other stuff.

[Fungus]

According to fungus, it might be even better to keep the scope at 100MHz due to aliasing (?).

Yes, but only when you turn on more than two channels. 

(and not just according to me, it's the math...)

[pope]

According to fungus, it might be even better to keep the scope at 100MHz due to aliasing (?).

Yes, but only when you turn on more than two channels. 

(and not just according to me, it's the math...)

Most of the times I use all 4 channels. So in this case you reckon I'll be better off by leaving the scope alone (i.e. 100MHz) ?

[Fungus]

Most of the times I use all 4 channels. So in this case you reckon I'll be better off by leaving the scope alone (i.e. 100MHz) ?

Not just 'reckon', I can prove it, mathematically. 

[BillyO]

Not just 'reckon', I can prove it, mathematically. 

I'd like to see that.

So, you are trying to tell us that, if I'm measuring, say a complex set of 4 signals, the scope will perform better if limited to 100MHz rather than 200MHz when measuring the same set of signals??

[Fungus]

So, you are trying to tell us that, if I'm measuring, say a complex set of 4 signals, the scope will perform better if limited to 100MHz rather than 200MHz when measuring the same set of signals??

At audio frequencies you won't see any difference.

With high frequency, real-world signals? Less aliasing.