Siglent SDS800X HD 12 bit DSO's

[Electro Fan]

Some times it is really annoying that still in this millenum with modern digital oscilloscopes we do not have freq reference input in most oscilloscopes and internal reference is very cheap simple xtal osc.

+1 for it would be nice to have more oscilloscopes provide a 10MHz reference input and output. 

(Request for Tautech - maybe you could suggest this to Siglent for scopes below the 5000 series.  Thx)

[tautech]

Some times it is really annoying that still in this millenum with modern digital oscilloscopes we do not have freq reference input in most oscilloscopes and internal reference is very cheap simple xtal osc.

+1 for it would be nice to have more oscilloscopes provide a 10MHz reference input and output. 

(Request for Tautech - maybe you could suggest this to Siglent for scopes below the 5000 series.  Thx)

Not possible in current generation.

Better frequency reference clocks are available in the higher priced products.....including optional OCXO.

[Martin72]

But can you really trust a development team which does not know how to count? 

If you don't like the program, you can switch TV channels.
If you don't like the axis labeling, you can switch it off.
Problem solved in both cases.
I value other things and that's a given with Siglent and Lecroy.
Clock:
The SDS2000Xplus series has a +/-1ppm clock,
2000X HD and 3000X HD +/-2ppm, with less aging.
I don't know whether an external master clock can offer great advantages in these cases.
This may be different for the smaller models with +/-25ppm without aging specifications, but I can hardly imagine that they would/will change anything in the low-low cost range.

[Martin72]

You have an opinion on it and express it, I have an opinion on it and express it, they can be the same, but they don't have to be.
This is an exchange of opinions, nothing less.
But no more than that.

[mawyatt]

Our expectations were set pretty high for the SDS814X HD based upon Performa01's excellent reviews/documentation here.

https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/

Saelig delivered yesterday mid-day, and we've had just a few moments to evaluate this new Siglent Instrument.

Even with the expectations set high, this new Instrument is nothing short of outstanding!

How Siglent has done this (at this price point) is quite amazing, so hat's off to them 

Now to try and get the Time NPT NTP Server setup!! Done
Bode Plot with Ext AWG LAN Done 

Best,

[Martin72]

Same here.
The word "game changer" is often used, but in this case it really is appropriate.
I'll be taking a closer look at the 804, sorry, 824, until my SDS3034X HD arrives.
But what I've seen in the last few days is unbelievable at this price.

[Electro Fan]

Some times it is really annoying that still in this millenum with modern digital oscilloscopes we do not have freq reference input in most oscilloscopes and internal reference is very cheap simple xtal osc.

+1 for it would be nice to have more oscilloscopes provide a 10MHz reference input and output. 

(Request for Tautech - maybe you could suggest this to Siglent for scopes below the 5000 series.  Thx)

Not possible in current generation.

Better frequency reference clocks are available in the higher priced products.....including optional OCXO.

No doubt in the current entry models (800, 1000, 2000, 3000) it isn't going to happen but going forward how about providing an external ref clock input so future entry models can take clock in (ie, not out, just in)?
Anyone with a GPSDO could provide a Ref Out to a scope's Ref In.

[baldurn]

No doubt in the current entry models (800, 1000, 2000, 3000) it isn't going to happen but going forward how about providing an external ref clock input so future entry models can take clock in (ie, not out, just in)?
Anyone with a GPSDO could provide a Ref Out to a scope's Ref In.

You could modify your scope in the same way as the popular Icom 9700 radio, that also lacks a true reference in. So people found out that exposure of the crystal in the radio to an external reference will cause it to lock and be disciplined.

[temperance]

@ pdenisowski

Edit:  Seriously, that is a really good example - I hope you wouldn't mind if I use it in a presentation someday

That's indeed an example I have been trying to explain to R&S many times but the reply has always been: Just use the zoom tools sir... That is The reason I don't have an R&S RTB or RTM or a new Trektopnix (Credit for that brand goes to a other forum member) or a Keysight. The SDS2000X HD can handle 400 Vpp at it's input with x1 probes without damage with excellent overdrive recovery. With 400 Vpp to work with I don't mind some overdrive and with a x10 or x100 probe it will be difficult to reach the limit. An R&S RTB or RTM can handle 40 Vpp an overdrive recovery is very bad.

I explained to an R&S sales person many times that there are applications were a 10 bit scope will run out of useful bits and overdrive recovery is important. I think he still doesn't understand what I was talking about.

An other example are 400 V powered half bridge converters or half bridge motor drives and similar power conversion circuits. MOSFET drivers don't like it when the half bridge node is driven too much below 0 V. 10 bits are not enough without some descent overdrive recovery to see what's going on. There are other examples in power electronics where overdrive recovery is important.

With my elderly TDS5 series I can measure the saturation behavior of power semiconductors or reverse recovery behavior without any trouble because overdrive recovery is almost invisible and the input can accept 150 Vpp.

An other very fine example is probing resonances caused by the inductance of bond wires in power semiconductor devices in an isolated SMPS which couple trough the transformer and make a product fail radiated emission tests. Of course, as some like to do, it is possible with some trial and error to put some filters here and there until it passes radiated emission tests. It's more interesting to know the origin of the problem and solve things with less components in less time. The design went from CM filters, ferrite beads and what not the 3 resistors and 2 capacitors and passed radiated emission tests without any further modifications.

Edit: this example has been debugged with an RTB3000 because the primary side was powered by 5V. But a similar problem has been found in direct off line converter. And the RTB3000 can't be used for such things.

[SHF]

What internal reference frequency does the SDS 804 have (25 MHz?)

[pdenisowski]

You could modify your scope in the same way as the popular Icom 9700 radio, that also lacks a true reference in. So people found out that exposure of the crystal in the radio to an external reference will cause it to lock and be disciplined.

I’ve actually done this modification to my 9700 using the Bodnar board - drove me crazy that I already had a lab full of very high quality Ref outs and the Icom didn’t have a true Ref In.

[SHF]

If you knew the internal ref cycle you could come up with something

[SHF]

the sds1104x works at 25 MHz,
Maybe the sds804 also with 25 MHz?

[pdenisowski]

that's indeed an example I have been trying to explain to R&S many times but the reply has always been: Just use the zoom tools sir... That is The reason I don't have an R&S RTB or RTM or a new Trektopnix (Credit for that brand goes to a other forum member) or a Keysight. The SDS2000X HD can handle 400 Vpp at it's input with x1 probes without damage with excellent overdrive recovery. With 400 Vpp to work with I don't mind some overdrive and with a x10 or x100 probe it will be difficult to reach the limit.

Thanks for the detailed post - that was very helpful in understanding the issue.

Johnnie Hancock wrote a great article about this topic:

https://www.electronicdesign.com/home/article/21200854/overcoming-overdrive-recovery

and I suspect I might get a similar answer when I ask our scope experts later today.  But let me look into this a little more and get back to you about what I find out.  Again, many thanks for the post!

[SHF]

right 25MHz

IC 10MHz ---> 25MHz

[mawyatt]

For the NTP Time Setup, we used NIST, Gaithersburg, Maryland USA,  IP address 129.6.15.26

Synched up in just a few seconds.

Here's addresses available at NIST, Gaithersburg:

129.6.15.26
129.6.15.27
129.6.15.28
129.6.15.29
129.6.15.30

Nice feature BTW

Best,

[temperance]

@ pdenisowski

The article is nice but it suggests the use of digital zoom tools and averaging. The idea works for stable wave forms in digital systems but not for power converters with feedback loops wiggling the duty cycle or resonant converters adjusting their switching frequency or controllers with spread spectrum modulation. The article also states that the distortion is caused by the Sin(x)/x reconstruction filter. I understand that but that's only one part of the problem. It is the true settling time which I'm after. Some Sin(x)/x distortion after an overdrive is fine and you can always revert to raw samples if that's a problem.

Edit: R&S has scopes with fast overdrive recovery such as the RTO series.

https://incompliancemag.com/rohde-a-schwarzs-rasrrto-series-oscilloscope-delivers-quick-overdrive-recovery/

The article in question covers exactly my case for fast overdrive recovery requirements.

[pdenisowski]

The SDS2000X HD can handle 400 Vpp at it's input with x1 probes without damage with excellent overdrive recovery.

I'm going to apologize in advance because I could have sworn I saw someone post a test of this (and, of course, I can't find it now), but how is overdrive recovery being tested / quantified?  It would have to be a function of the amount / amplitude of the overdrive (perhaps expressed in divisions) and the duration of the overdrive (how long the ADC is saturated).

I've been looking into this and there seems to be very little consensus (or very little of anything) regarding how overdrive recovery is quantified.

[mawyatt]

No doubt in the current entry models (800, 1000, 2000, 3000) it isn't going to happen but going forward how about providing an external ref clock input so future entry models can take clock in (ie, not out, just in)?
Anyone with a GPSDO could provide a Ref Out to a scope's Ref In.

You could modify your scope in the same way as the popular Icom 9700 radio, that also lacks a true reference in. So people found out that exposure of the crystal in the radio to an external reference will cause it to lock and be disciplined.

This is called Injection Locking and first discovered by Van der Pol while investigating Neon bulb relaxation oscillators. He noted that two Neon oscillators blinked exactly at the same rate when powered from the same battery (coupling), then developed the non-linear theory to describe such.

We've utilized this technique in the past and even developed a unique microwave receiver based upon Injection Locking to the transmitted signal (Patent 5603111) where the Injection Locking tracked and demodulated (AM and FM) the input signal.

You can often injection lock a crystal oscillator by applying a low level signal to the VCC or Ground oscillator terminal, usually just adding a small resistor (5~10 ohms) in series with VCC or Ground, then a small capacitor to couple the locking signal. Recall some folks here did this with a GPS Reference oscillator on a cheap AWG generator awhile back.

If you are interested in Injection Locking, here's a link to a Peltz Oscillator Injection Locking utilizing the Bode Function in SDS2000X+, maybe someone will try this with the SDS800X HD 

https://www.eevblog.com/forum/projects/injection-locked-peltz-oscillator-with-bode-analysis/msg4424434/#msg4424434

Best,

[temperance]

@ pdenisowski

I edited my posts. It now contains a link to an article about the RTO series and why overdrive recovery is important in some applications.

The SDS2000X HD can handle 400 Vpp at it's input with x1 probes without damage with excellent overdrive recovery.

The Signlent however is still nowhere near a TDS5054 and takes about 100 ns to recover.

[pdenisowski]

Edit: R&S has scopes with fast overdrive recovery such as the RTO series.

https://incompliancemag.com/rohde-a-schwarzs-rasrrto-series-oscilloscope-delivers-quick-overdrive-recovery/

The article in question covers exactly my case for fast overdrive recovery requirements.

Lol - thanks!  Mike was one of the people I was going to talk to about this today  

Still would be very interested in hearing how people (here) are quantifying overdrive recovery.  Doesn't seem that easy to do.

[Performa01]

Johnnie Hancock wrote a great article about this topic:

https://www.electronicdesign.com/home/article/21200854/overcoming-overdrive-recovery

Yes, Johnnie Hancock just states the obvious: do not overdrive your oscilloscope frontend. Just don't do it, no matter what use case you come up with. Just bcause a use case exists, that's no excuse to abuse a (maybe inadequate) tool.

Especially with modern high resolution DSOs, we do have alternatives. Even when we really need that much of a dynamic range, because the desire to analyze a small detail in a high-amplitude waveform, there would be alternative approaches with modern high resolution DSOs, so that we don't need to overdrive the oscilloscope frontend and risk overload (recovery) distortions.

In my thread I've demonstrated multiple times how vertical zoom in combination with certain math functions (I've preferred to use Average on periodic signals, but ERES could be used as well) can increase the resolution up to 16 bits and reduce the noise at the same time, so that high zoom factors become perfectly usable - that's pretty much what Johnnie Hancock recommends in his article.

Johnnie Hancock only talked about the overload recovery times of the semiconductor amplifiers, where semiconductor components require a certain time to recover from saturation. Of course we have to deal with that in Siglent oscilloscopes as well, namely in the integrated PGAs from a reputable major semiconductor manufacturer, but there recovery times are more in the below-one-nanosecond region and certinly not much of a concern for a 200 MHz DSO.

What Johnnie Hancock forgot to mention, is the much more important problematic overload recovery behaviour of the split path input buffers in DSO frontends, as they are universally used for general purpose oscilloscopes. These offer reasonably stable DC offset even with high bandwidth frontends. While the LF-path will clip cleanly and its recovery time doesn't matter because the signals here won't exceed one kilohertz or so anyway, the HF-path differentiates the signal instead of clean clipping, hence throwing it out of sync with the LF path. Here we are not talking about nano- but milliseconds!

Btw: the higher the offset compensation capability of a scope frontend with split path input buffer, the more potential problems might occur.

[temperance]

@ Performa01

Thanks, I noticed that and I will experiment with that instead. Of course it takes much more fiddling with settings and averaging is not always possible in power converters. Unfortunately I don't have the funds to buy an R&S RTO. Otherwise I would have do so.

I don't consider overdrive abuse if the signal is well within the maximum range of 400 Vpp in case of the 2000 and recovery distortions are not such a problem. It is being blind for 100 µs or more which bothers me.

[mawyatt]

You can often injection lock a crystal oscillator by applying a low level signal to the VCC or Ground oscillator terminal, usually just adding a small resistor (5~10 ohms) in series with VCC or Ground, then a small capacitor to couple the locking signal. Recall some folks here did this with a GPS Reference oscillator on a cheap AWG generator awhile back.

Here's a DIY project to do this on "can"-packaged crystal oscillators:
https://ka7oei.blogspot.com/2023/03/injection-locking-cheap-crystal-can.html

I don't think I am quite ready yet to try it on my SDS814X HD...

That seems more complex than necessary with the transistor, inductor and other components. We had success with just a small R in series with VCC/VDD (Or Ground), and small C coupling to the R. It doesn't take much energy to lock the oscillator if the frequency is close.

Like you I'm not going to butcher hack our new 814!!!

Best, 

[TopQuark]

The SDS2000X HD can handle 400 Vpp at it's input with x1 probes without damage with excellent overdrive recovery.

I'm going to apologize in advance because I could have sworn I saw someone post a test of this (and, of course, I can't find it now), but how is overdrive recovery being tested / quantified?  It would have to be a function of the amount / amplitude of the overdrive (perhaps expressed in divisions) and the duration of the overdrive (how long the ADC is saturated).

I've been looking into this and there seems to be very little consensus (or very little of anything) regarding how overdrive recovery is quantified.

Well I was curious about overdriving the frontend on my SDS2000X HD.

I've setup my function gen to output a 500ns pulse at 100kHz. Both probes used for the measurement are 1x 55MHz passive probes (CT4200), which is nice as both 1x probes don't require perfect matching of probe compensation to get comparable readings. Both probes measure the same point of the output signal using a BNC T-split connector and probe tip to BNC adapters.

I've inserted a loop between the function generator output and the measurement point to create some inductive nastiness, so that we have more interesting ringing waveforms to look at. Also the higher tip capacitance of the 1x probes should also add to the ringing.

CH3 is set to 5V/div capturing the whole pulse waveform, CH1 is set to 500mV/div so that it is overdriven. CH3 is then digitally zoomed to 500mV/div, and offset is adjusted so that the overdriven and digitally zoomed waveforms overlap.

The results is actually better than I expected. The rising edge ringing matches pretty well between the two channels, the falling edge ringing is a bit distorted, but the general shape of the signal is still comparable. Changing the overdriven channel's vertical offset will change the waveform depending on the offset value, so this measurement technique is still not a good idea.

Also with 12 bits of vertical resolution, I don't think we need to resort to overdriving the input channels to see signal details anymore.