Choosing between entry-level 12-bit DSOs

[Mechatrommer]

What is the length of your Lanczos filter?

well this is quite embarassing iirc i set "wing" length as small as possible due to some complication i encountered earlier, extra ringing? iirc... length only like 2 or 3 i dont have indepth knowledge about it and its effect. thanks for your info, i'll looking into it deeper later...

[gf]

What is the length of your Lanczos filter?

well this is quite embarassing iirc i set "wing" length as small as possible due to some complication i encountered earlier, extra ringing? iirc... length only like 2 or 3 i dont have indepth knowledge about it and its effect. thanks for your info, i'll looking into it deeper later...

With a single-sided length of 3 (double-sided length 6), you should be able to reconstruct up to ~140 MHz at 500 MSa/s with less than 1% interferences.

I just don't know if you measure the length in the same way as I do, therefore I have added the plots to show what I mean with lenght 3.

[Mechatrommer]

I just don't know if you measure the length in the same way as I do, therefore I have added the plots to show what I mean with lenght 3.

you can see in the github code i linked earlier. "width property is half a wing" what wing and internal working of it, i havent dig deeper, maybe later. from your description, lanczos width is 2 * wing size, so my wing is 2 meaning lanczos width is probably 4 or 5? anyway you gave me some idea about lanczos limitation related to its width. i'll keep that in mind. thanks and cheers.

[Martin72]

What was the topic again?
Question for a friend...

[Harrow]

Since we are so far off topic, I guess it's okay for me to ask an incidental question. While all this conversation is quite interesting and instructive, I'm curious how many people actually use or need bandwidth or sampling beyond 100 MHz and 312.5 S/s? Presumably, anyone working in comms, but who else? My thought process when buying the DHO800 was that even with 4 channels operating, I still have enough sampling to adequately cover the 100 MHz capability of the scope with the included 150 MHz probes being well clear of having any attenuation effect at 100 MHz.

For example, here are some waveforms from a buck convertor I designed and built this week running at 100 kHz. (Note the oscillations on switching are mostly due to using the clip-on scope probes...when I use the spring and tip, the yellow gate drive signal is clean and the overshoots on the cyan and magenta traces halve.)

My question is....for the kind of work I'm doing (hobbyist audio and SMPS in the 100 W to 5 kW range), what would be the benefits, if any, in me having a more capable scope? (Please excuse my ignorance, as my professional background is 50 Hz HV & EHV transmission)

[Fungus]

Since we are so far off topic, I guess it's okay for me to ask an incidental question. While all this conversation is quite interesting and instructive, I'm curious how many people actually use or need bandwidth or sampling beyond 100 MHz and 312.5 S/s?

This is a very good question.

Even at 100Mhz the probing method and all those little cables on your breadboard will dominate any measurement and you need knowledge/experience to interpret what's on the screen.

Presumably, anyone working in comms, but who else? My thought process when buying the DHO800 was that even with 4 channels operating, I still have enough sampling to adequately cover the 100 MHz capability of the scope with the 150 MHz probes being well clear of having any attenuation effect at 100 MHz.

You have to be slightly careful here because the measured bandwidth of the Rigols is much higher than what the label says.

In reality the "70Mhz" model has 125Mhz bandwidth and the "100Mhz" model has 200Mhz bandwidth.

The probes have also been tested and are good for both.

My $0.02:

You could easily argue that "125Mhz" is the optimum configuration for a DHO800 and that it's as much as a hobbyist needs.

I wouldn't disagree.

As noted above: Probing dominates, even at these "low" frequencies.

eg. The difference between "probes" and "springs" is huge and I hardly ever use the springs (they're a pain in the ass).

I admit I usually have my DHO804 set to "200Mhz" because ... well ... I'm not sure. It's a head thing, I don't believe there's a practical difference for me in my "Arduino" work. The difference on screen is tiny and mostly swamped by probing (see above).

I'm not saying that nobody needs the extra 75MHz but you have to be into coax cables and 50 Ohm terminators to take advantage of it. If that's your case then fine. People who poke handheld probes at circuits? Not so much.

(I also think "200Mhz" is a very arbitrary number - why does no Siglent owner ever need 300Mhz?)

[Fungus]

Somebody just added a full screen mode to the Rigol... 

https://www.eevblog.com/forum/testgear/hacking-the-rigol-dho800900-scope/msg5471431/#msg5471431

[ebastler]

Let's see whether they are brave enough to distribute this hack (and other related ones). The DHO1000 hacking took a similar approach of decompiling and patching the executables, back in December. I keenly followed that effort, since I had a DHO1074 at the time and was hoping to see the 50 Ohm inputs and 400 MHz bandwidth enabled.

Back then, the developer(s) never made their modifications available to others and eventually pulled the plug on that effort -- due to legal concerns in my understanding. Rigol does explicitly forbid reverse engineering and decompiling in their license terms. Of course we have not seen them act on this, but who is willing to run the experiment?

[shapirus]

Let's see whether they are brave enough to distribute this hack (and other related ones). The DHO1000 hacking took a similar approach of decompiling and patching the executables, back in December. I keenly followed that effort, since I had a DHO1074 at the time and was hoping to see the 50 Ohm inputs and 400 MHz bandwidth enabled.

Back then, the developer(s) never made their modifications available to others and eventually pulled the plug on that effort -- due to legal concerns in my understanding. Rigol does explicitly forbid reverse engineering and decompiling in their license terms. Of course we have not seen them act on this, but who is willing to run the experiment?

Distributing patches, at least, should be legally clean. Don't quote me on this, though. Besides, there was a point about GPLed code being used in the apk. I don't know if it is so, but there seem to be a lot of standard android stuff included. Not sure what license it has.

[Mechatrommer]

Somebody just added a full screen mode to the Rigol... 

charming indeed but... the hidden complication is "not signed" app meaning no access to system file, cannot do screen capture. thats why be careful making post like this in beginner section. i know there's post about deactivating signing but i dont want to dig deeper until they finalize it. its still in R&D stage.

What was the topic again?
Question for a friend...

discussion about nyquist, that lead to proper Sinc reconstruction reveals siglent DHO800X can do it properly unlike Rigol, this can also can help user make decision whether this is important or not. this discussion can also make newbie aware of some technical and theory informations. for me Sinc reconstruction is important when signals contains spectral near Sr / 2, let alone if more than that.

Since we are so far off topic, I guess it's okay for me to ask an incidental question. While all this conversation is quite interesting and instructive, I'm curious how many people actually use or need bandwidth or sampling beyond 100 MHz and 312.5 S/s?

you never know what lie ahead of you. not so long ago, i deal with opamp circuit that experience oscillation beyond nyquist limit, granted BW limited siglent may suppressed this signal, but with rigol, i saw some nasty oscillation, but with betterer Sinc reconstruction, it may help distinguish some of signal near nyquist limit. if you can limit yourself to arduino circuit, you may not be aware of this and you are safe with rigol. but if you dont have enough belt color, unaware probing 250MHz spectral at 312.5MSps may bite you. ymmv.

[tggzzz]

Since we are so far off topic, I guess it's okay for me to ask an incidental question. While all this conversation is quite interesting and instructive, I'm curious how many people actually use or need bandwidth or sampling beyond 100 MHz and 312.5 S/s? Presumably, anyone working in comms, but who else? My thought process when buying the DHO800 was that even with 4 channels operating, I still have enough sampling to adequately cover the 100 MHz capability of the scope with the included 150 MHz probes being well clear of having any attenuation effect at 100 MHz.

For example, here are some waveforms from a buck convertor I designed and built this week running at 100 kHz. (Note the oscillations on switching are mostly due to using the clip-on scope probes...when I use the spring and tip, the yellow gate drive signal is clean and the overshoots on the cyan and magenta traces halve.)

My question is....for the kind of work I'm doing (hobbyist audio and SMPS in the 100 W to 5 kW range), what would be the benefits, if any, in me having a more capable scope? (Please excuse my ignorance, as my professional background is 50 Hz HV & EHV transmission)

Back in the late 70s and early 80s 100MHz was suitable for TTL and LSTTL logic. Since then logic speeds have increased "a bit", so the required bandwidth has increased "a bit".

Note that the inputs/outputs of logic gates are analogue signals that are interpreted by the receiver as digital signals. In order for the interpretation to be correct, the analogue waveforms have to meet the specifications, e.g. min/max voltages and over/undershoots, timing (the hold time, t_H, is particularly tight), clock edge rates and monotonicity, etc. Ensuring all that is in order is called "signal itegrity", and the required bandwidth depends only on the transition time; a clock/signal period is completely irrelevant.

As others have noted, at such speeds the probes become an integral part of the circuit and measurement. Start by working out the input impedance of a typical 10Mohm/15pF probe at  100MHz; rather than 10000kohms, it is more like 0.1kohms Then add the inductance of a 6"/150mm ground lead, and calculate the resonant frequency with the 15pF tip capacitance.

Nowadays jellybean logic has edge rates of 1ns, and faster. That translates to 350MHz, and higher.

[Fungus]

Somebody just added a full screen mode to the Rigol... 

charming indeed but... the hidden complication is "not signed" app meaning no access to system file, cannot do screen capture. thats why be careful making post like this in beginner section.

Screen capture over network still works even on an unsigned app.

[Mechatrommer]

Screen capture over network still works even on an unsigned app.

not everybody like to connect to network for a mere screen capture, i do it with usb stick. my ethernet cable is super long and its quite a mess trying to run it to my dso, at my lab setup, connecting to usb cable is much easier. and that luckily i have ethernet cable at all so i can do some adb hack albeit a bit inconvenience. ymmv.

[Fungus]

that lead to proper Sinc reconstruction reveals siglent DHO800X can do it properly unlike Rigol, this can also can help user make decision whether this is important or not.

When was THAT proven?

Siglent has a higher sample rate.

Rigols aren't forced to work at 312.5MS/sec.

[ebastler]

that lead to proper Sinc reconstruction reveals siglent DHO800X can do it properly unlike Rigol, this can also can help user make decision whether this is important or not.

When was THAT proven?

In reply #465, 2N3055 showed stable reconstruction of a 220 MHz sine which was sampled at 500 MSa/s. So the SDS800X HD can still resonstruct properly at a sampling rate of less than 2.5x of the signal frequency, while the Rigol started to show wobbles at 3x or so.

Let's call it a demonstration, not a "proof", since this was just a quick one-off test.

[2N3055]

that lead to proper Sinc reconstruction reveals siglent DHO800X can do it properly unlike Rigol, this can also can help user make decision whether this is important or not.

When was THAT proven?

In reply #465, 2N3055 showed stable reconstruction of a 220 MHz sine which was sampled at 500 MSa/s. So the SDS800X HD can still resonstruct properly at a sampling rate of less than 2.5x of the signal frequency, while the Rigol started to show wobbles at 3x or so.

Let's call it a demonstration, not a "proof", since this was just a quick one-off test.

Loot at the post :

********************
When was THAT proven?

Siglent has a higher sample rate.

Rigols aren't forced to work at 312.5MS/sec.
********************

So :
He knows it was proven and when.
He knows Siglent has higher, sufficient sampling as opposed to Rigol.
He knows Rigol does not do it right but "Rigols are not forced to at 312.5MS/sec.", which is absolutely lie for a 4ch version.

All of that mean he knows the truth. He is trying to bend it..

[Fungus]

Screen capture over network still works even on an unsigned app.

not everybody like to connect to network for a mere screen capture, i do it with usb stick. my ethernet cable is super long and its quite a mess trying to run it to my dso, at my lab setup, connecting to usb cable is much easier. and that luckily i have ethernet cable at all so i can do some adb hack albeit a bit inconvenience. ymmv.

Cable? My WiFi adapter cost me $7...

[Fungus]

Nowadays jellybean logic has edge rates of 1ns, and faster. That translates to 350MHz, and higher.

Yep. If you're really into "logic" then a Rigol MSO5000 is the way to go.

[Fungus]

In reply #465, 2N3055 showed stable reconstruction of a 220 MHz sine which was sampled at 500 MSa/s. So the SDS800X HD can still resonstruct properly at a sampling rate of less than 2.5x of the signal frequency, while the Rigol started to show wobbles at 3x or so.

I'd like to see a frequency sweep.

The Rigol is applying the theory correctly and the Siglent can't possibly be doing an infinitely wide reconstruction, so... 

[shapirus]

BTW, speaking of signal integrity, the (unlocked) Rigol can more or less properly show signals at up to 500 MHz at 1.25 Gsa/s (the 2.5x ratio again btw), albeit with a greatly reduced amplitude, apparently because of the hardware low-pass filter on the input.

While not suitable for measurements, it will at least allow to see qualitatively if there are any unwanted oscillations up to 500 Mhz. The frequency counter fails by that time (maybe because of the reduced amplitude), but the waveform looks all right and proper frequency if you measure it using cursors.

I think it may make sense, as was suggested by several people, to mod the input filter on one of the channels (say ch4) and reserve it for the cases when a higher bandwidth input is required. Of course, that, as usual, requires to understand the limitations, knowing how to probe at those frequencies, etc.

[ebastler]

The Rigol is applying the theory correctly

When was THAT proven? 

Rigol have repeatedly cut corners in their signal processing. The sampling rate vs. bandwidth mismatch has been discussed at length here; the very generous inter-channel skew spec, wobbly AC trigger, wonky FFT "resolution bandwidth", incorrect flat-top window function come to mind as well. I would not be surprised at all if they had not gotten the Sinc interpolation quite right.

[shapirus]

I'd like to see a frequency sweep.

I second this.

@KungFuJosh can you please set the scope to 500 Msa/s, low waveform acquisition rate (to make the TinySA's glitches less visible), low persistence, and record a video of a 30 seconds long frequency sweep from, say, 110 MHz to 270 MHz?

Coax connection with a 50 Ohm feed-through terminator, if possible, to make the test conditions the same as in my test.

It will be interesting to see at what frequencies (and at what ratio relative to the sampling rate) it will become first wobbly and then AM-like (if it will), to compare that to Rigol.

[Mechatrommer]

Screen capture over network still works even on an unsigned app.

not everybody like to connect to network for a mere screen capture, i do it with usb stick. my ethernet cable is super long and its quite a mess trying to run it to my dso, at my lab setup, connecting to usb cable is much easier. and that luckily i have ethernet cable at all so i can do some adb hack albeit a bit inconvenience. ymmv.

Cable? My WiFi adapter cost me $7...

iircsomeone stated dho800 only works on specific brand. i have few wifi adapter here, maybe later i will try. but still, its a few more steps to do... rather than plugin usb stick and hit capture button. ymmv.

BTW, speaking of signal integrity, the (unlocked) Rigol can more or less properly show signals at up to 500 MHz at 1.25 Gsa/s (the 2.5x ratio again btw), albeit with a greatly reduced amplitude, apparently because of the hardware low-pass filter on the input.

this is +1 imho in rigol, lets not forget, the 2 scopes discussed here got pros and cons.

In reply #465, 2N3055 showed stable reconstruction of a 220 MHz sine which was sampled at 500 MSa/s. So the SDS800X HD can still resonstruct properly at a sampling rate of less than 2.5x of the signal frequency, while the Rigol started to show wobbles at 3x or so.

I'd like to see a frequency sweep.

2n**55 only showed one successsful case at Sr / 2.27, but i bet anything lower freq than that will be better, the only thing is at when higher freq will start wobbly up to extreme 250MHz.

The Rigol is applying the theory correctly and the Siglent can't possibly be doing an infinitely wide reconstruction, so... 

i havent seen that proven, in fact shapirus proved that otherwise. dont show too much of fanboyism, we trust more scientific facts rather than sentimental facts we have saying/joke in our medsos group, if we have stupid in ourself, its ok, but dont reveal it too much, keep it some for next generation no pun/insult intended cheers.

[shapirus]

not everybody like to connect to network for a mere screen capture, i do it with usb stick. my ethernet cable is super long and its quite a mess trying to run it to my dso, at my lab setup, connecting to usb cable is much easier. and that luckily i have ethernet cable at all so i can do some adb hack albeit a bit inconvenience. ymmv.

Well, installing a modded apk already requires a certain level of involvement, way beyond a normal user's one, and of course there's a certain learning curve. Disabling apk signature verification is not much farther than that (especially since a respective modded .jar that can be used without having to build your own is available).

So there's not much more work to do if you want to retain the screenshot functionality after you already know how to change stuff on the file system and install a modded apk (or even rebuild your own).

The overall point is that such mods are possible and they don't require top hacker skills or hardware modifications (not even connecting via the serial port). But opening the case may be necessary: before changing anything on the android file system(s), it is highly recommended to take a backup of the internal SD card to have an image that you can restore to if something goes wrong.

p.s. a significant "+1" for Rigol is that its software is stored on a standard micro SD card. This is great not only for modding, but for creating and restoring backups. But where is the data stored on the Siglent? Some soldered-in flash storage chip?

[shapirus]

this is +1 imho in rigol, lets not forget, the 2 scopes discussed here got pros and cons.

Since the Siglent can into 2 Gsa/s, it could potentially be modded to support at least 800 MHz single-channel bandwidth, if there are no further limitations in digital signal processing and/or software. I don't recall anyone mentioning or trying this though.