Is 100Mhz enough? (calculations + charts included)

[tautech]

If you can stretch your budget a little more there is the SDS1104X-E which can be hacked to 200MHz.

OooOooo. So the U is the wimpy version of the E, but kinda 'pretend' wimpy where its downgraded in the firmware aye. This is a rabbit hole worth looking into.

No the X-U is a different design with a quite different features set.
X-E uses 2 ADC's whereas X-U only one therefore X-U sampling rate is only sufficient to 100 MHz with all channels active.
Attached is a comparison chart.

[NaxFM]

If you can stretch your budget a little more there is the SDS1104X-E which can be hacked to 200MHz.

OooOooo. So the U is the wimpy version of the E, but kinda 'pretend' wimpy where its downgraded in the firmware aye. This is a rabbit hole worth looking into.

Unfortunately not, It's really a different design with more limited front end, single ADC and no circuitry for mixed signal, maybe even the FFT is more limited, but i'm not sure about that.
With 100 bucks more you get a 200MHz scope with dual ADC , to me is a no brainer, the 1104-U shouldn't even exist in my opinion. If I was (and I am) on a tight budget i'd simply wait to collect more money to buy the 1104-E instead of bying the 1104-U right away

[Fungus]

To me the 1104-U is really not worth the money.
The 1104-E, for 100 bucks more gives you much, MUCH more.

Yep. The E version is crippled. The 2 channel Siglents are also missing a lot of features.

The two 'scopes worth considering in this price range are: Rigol DS1054Z and Siglent SDS1104X-E.

The Siglent is 'better', yes, but it costs about 45% more so it ought to be. The Rigol is a perfectly good 'scope though.

Decide on your budget then the choice is made for you.

[tautech]

To me the 1104-U is really not worth the money.
The 1104-E, for 100 bucks more gives you much, MUCH more.

Yep. The E version is crippled. The 2 channel Siglents are also missing a lot of features.

Not so SDS2202X-E which has a very similar feature set to the 4ch X-E's.

[Fungus]

Yep. The E version is crippled. The 2 channel Siglents are also missing a lot of features.

Not so SDS2202X-E which has a very similar feature set to the 4ch X-E's.

Siglent's naming department rocks!

[tautech]

Yep. The E version is crippled. The 2 channel Siglents are also missing a lot of features.

Not so SDS2202X-E which has a very similar feature set to the 4ch X-E's.

Siglent's naming department rocks!

Simple isn't it.
2= 2 GSa/s, 20= 200 MHz, 2= 2ch, X-E models have similar but slightly different feature sets.

[NaxFM]

Simple isn't it.
2= 2 GSa/s, 20= 200 MHz, 2= 2ch, X-E models have similar but slightly different feature sets.

Never occurred to me that the first number was the maximum sampling rate, everything is clearer now!

[pepelevamp]

To me the 1104-U is really not worth the money.
The 1104-E, for 100 bucks more gives you much, MUCH more.

Yep. The E version is crippled. The 2 channel Siglents are also missing a lot of features.

The two 'scopes worth considering in this price range are: Rigol DS1054Z and Siglent SDS1104X-E.

The Siglent is 'better', yes, but it costs about 45% more so it ought to be. The Rigol is a perfectly good 'scope though.

Decide on your budget then the choice is made for you.

OH mate, thats a great looking Rigol. Got me thinking now - would 50MHz be enough for my project? It might be actually. Damn, why do I have to be nerding with such fast signals. I can offer a reason as to why these Siglents were on my to-buy list - its because they're passively cooled with no fans. I have hyperacusis. The pain threshold for my hearing is too low. Eeeeeeverything irritates the crap out of me.

[pepelevamp]

If you can stretch your budget a little more there is the SDS1104X-E which can be hacked to 200MHz.

OooOooo. So the U is the wimpy version of the E, but kinda 'pretend' wimpy where its downgraded in the firmware aye. This is a rabbit hole worth looking into.

No the X-U is a different design with a quite different features set.
X-E uses 2 ADC's whereas X-U only one therefore X-U sampling rate is only sufficient to 100 MHz with all channels active.
Attached is a comparison chart.

Thank you Tautech - your chart is super helpful. Its a pretty obvious choice to get the E series aye. I just need to confirm if this scope indeed is passively cooled.

[Fungus]

OH mate, thats a great looking Rigol. Got me thinking now - would 50MHz be enough for my project? It might be actually. Damn, why do I have to be nerding with such fast signals. I can offer a reason as to why these Siglents were on my to-buy list - its because they're passively cooled with no fans. I have hyperacusis. The pain threshold for my hearing is too low. Eeeeeeverything irritates the crap out of me.

You can EASILY unlock the Rigol DS1054Z to 100MHz.

Enter your serial number on this page and it generates a key for you: http://gotroot.ca/rigol/riglol/

The only key you need these days is DSEA, everything else comes as standard. You can also remove the unlock just as easily and go back to 50Mhz if you ever need to.

Fanless Siglents? Where did you get that from?    Quieter fan swaps are common in both Rigols and Siglents.

[nctnico]

Then again, the OPs project goals make next to no sense at all so there is little use in suggesting anything. An oscilloscope is not a high precision instrument for measuring amplitudes anyway. If the OP wants to measure DAC steps accurately, then he/she needs to set the DAC to a specific output code (DC level) and use a >4.5 digit DMM to measure the DAC's output value.

The world will be a better place without people such as yourself who lean into providing 'advice' yet belittle projects at the same time - all before you even understand what is happening.

Well, In have been designing circuits professionally for decades and have used & owned more different oscilloscopes (from low end to very high end) compared to the average forum member. And yet up to my post the details you posted prevented me from making a useful suggestion to you. I prefer to stay on the safe side. Judging from how you are still jumping between various models based on the latest suggestions, I strongly suggest you make a list with pros and cons for various models and make a decission based on that. Try to make a comparison between the Tektronix TDS 2024B you have used before; what did you like and what didn't you like about it. Shared and individual channel controls can make a difference but the lower cost models suggested so far have shared controls where the TDS 2024B has individual channel controls. In the low cost segment GW Instek is one of the few brands that have individual channel controls (GDS-1054B is a very cheap 4 channel model with individual channel controls).

However, none of the models suggested so far is fanless. A requirement which should have been in your first post. Many people are replacing the fans in their oscilloscopes with lower noise models for better comfort (but likely voiding warranty). Rohde & Schwarz made fanless DSOs up to recently; look for HMO1000 series (for example: https://www.batronix.com/shop/rohde-schwarz/HMO1000.html). These likely can be found on the second hand market and at equipment dealers.

[pepelevamp]

Then again, the OPs project goals make next to no sense at all so there is little use in suggesting anything. An oscilloscope is not a high precision instrument for measuring amplitudes anyway. If the OP wants to measure DAC steps accurately, then he/she needs to set the DAC to a specific output code (DC level) and use a >4.5 digit DMM to measure the DAC's output value.

The world will be a better place without people such as yourself who lean into providing 'advice' yet belittle projects at the same time - all before you even understand what is happening.

Well, In have been designing circuits professionally for decades and have used & owned more different oscilloscopes (from low end to very high end) compared to the average forum member. And yet up to my post the details you posted prevented me from making a useful suggestion to you. I prefer to stay on the safe side. Judging from how you are still jumping between various models based on the latest suggestions, I strongly suggest you make a list with pros and cons for various models and make a decission based on that. Try to make a comparison between the Tektronix TDS 2024B you have used before; what did you like and what didn't you like about it. Shared and individual channel controls can make a difference but the lower cost models suggested so far have shared controls where the TDS 2024B has individual channel controls. In the low cost segment GW Instek is one of the few brands that have individual channel controls (GDS-1054B is a very cheap 4 channel model with individual channel controls).

However, none of the models suggested so far is fanless. A requirement which should have been in your first post. Many people are replacing the fans in their oscilloscopes with lower noise models for better comfort (but likely voiding warranty). Rohde & Schwarz made fanless DSOs up to recently; look for HMO1000 series (for example: https://www.batronix.com/shop/rohde-schwarz/HMO1000.html). These likely can be found on the second hand market and at equipment dealers.

I don't care about how good you are at scopes with an attitude like yours. I don't need someone telling me to write down what I like & dislike about scopes & telling me how to make decisions. I have select posts for specific criteria. Just get lost - you aren't helpful.

[pepelevamp]

OH mate, thats a great looking Rigol. Got me thinking now - would 50MHz be enough for my project? It might be actually. Damn, why do I have to be nerding with such fast signals. I can offer a reason as to why these Siglents were on my to-buy list - its because they're passively cooled with no fans. I have hyperacusis. The pain threshold for my hearing is too low. Eeeeeeverything irritates the crap out of me.

You can EASILY unlock the Rigol DS1054Z to 100MHz.

Enter your serial number on this page and generates a key for you: http://gotroot.ca/rigol/riglol/

The only key you need these days is DSEA, everything else comes as standard.

Fanless Siglents? Where did you get that from?    Quieter fan swaps are common in both Rigols and Siglents.

Yeah mate - I had these written down as fanless for someeee reason.  Mind you look at the fan in these guys.  Tiny wee things. Must sound like an RC car whizzing around.
Thank you for the link - thats very helpful. Its just the processor that gets cool aye? And the FPGA? Digital stuff. I had horrors about me changing the fan & upsetting some carefully balanced caps or something & having bung measurements forever.

EDIT: Watching the eevblog teardown - that aint no buzzy fan. 18dBA. Smells good to me.

[Fungus]

Yeah mate - I had these written down as fanless for someeee reason.  Mind you look at the fan in these guys.  Tiny wee things. Must sound like an RC car whizzing around.
Thank you for the link - thats very helpful. Its just the processor that gets cool aye? And the FPGA? Digital stuff. I had horrors about me changing the fan & upsetting some carefully balanced caps or something & having bung measurements forever.

Nah, it's easy. Just a standard fan connector like in a PC. Ten minutes work with a screwdriver to take the back off and swap it.

Edit: I used this one in my Rigol and the difference was massive. I wish I'd done it on the first day I got the 'scope.

https://www.eevblog.com/forum/testgear/rigol-ds1054z-ds1000z-fan-noise/msg1228358/#msg1228358

[tautech]

If you can stretch your budget a little more there is the SDS1104X-E which can be hacked to 200MHz.

OooOooo. So the U is the wimpy version of the E, but kinda 'pretend' wimpy where its downgraded in the firmware aye. This is a rabbit hole worth looking into.

No the X-U is a different design with a quite different features set.
X-E uses 2 ADC's whereas X-U only one therefore X-U sampling rate is only sufficient to 100 MHz with all channels active.
Attached is a comparison chart.

Thank you Tautech - your chart is super helpful. Its a pretty obvious choice to get the E series aye. I just need to confirm if this scope indeed is passively cooled.

None we stock from Siglent are without fans. If you want the horsepower you have to cool the engine. 
The quietest we stock is the 2ch SDS1202X-E which is running a single ADC.
Pop out to see us with no commitment to buy and judge the fan noise for yourself.

[kcbrown]

The Teensy 4.0 (and 4.1) uses an NXP MIMXRT1062-DVL6A, which is another order of magnitude faster than the MK20DX256VLH7.  Its datasheet doesn't specify the slew rate or bandwidth of its DAC, so I can't say what to expect with it, but even if we assume an order of magnitude improvement in the slew rate, that's still easily within the 100 MHz scope's ability to see the edge clearly.


Put another way, the bandwidth of the output of your Teensy is almost certainly easily within the 100 MHz scope's ability to faithfully show anything you generate with it.

Thanks mate this is great advice. I appreciate your help going into detail with the slew rate.  Yup I got the Teensy 4.0. I'm really going hardout on the CPU.
I'm using parallel-IO into a resistor ladder instead of using the built-in DACs because its been too hard to sync the DAC to digital IO.

Its way, way, waaaaaaaaaaay faster - at least on my SAM3XE on my Arduino DUE. Waaaaaaaaaaaaay faster.

Well, in that case, then the effective slew rate is going to be the result of a combination of the slew rate of your parallel I/O pins and the RC time constant of your resistor ladder.  This is where you get into some tradeoffs.  You can use lower value resistors in your ladder, but if you do so then your parallel lines will have to source more current, and there will be limits to that (not to mention that the load impedance might well affect the slew rate of the output pins).

Because you're moving to a Teensy 4.0, but your experience is with the Arduino Due, you may need to perform some experiments to see whether your approach is really worth going with, as opposed to using the internal DAC.


In any case, most microcontrollers I'm aware of don't even come close to the limits of a 100 MHz scope when it comes to seeing the timing of the signal edges on the I/O pins.  This really shouldn't be much of a surprise.  Extremely fast edges on the outputs start to demand a lot more work on the board layout and the load in order to avoid ringing.  In essence, you start to come up against transmission line considerations if you attempt to drive the output too hard, and most microcontroller boards like the Teensy are oriented towards hobbyists using breadboards and other inexpensive prototyping mechanisms wherein things like transmission line impedance matching aren't being considered.

So the bottom line here is that I think you'll be quite well off with even an entry level 100 MHz scope for this. 


At this point, I think it's going to be worth asking what your expected future use cases will be and what your budget is.  Different scopes have different things that they're particularly good at, so it would be helpful to have a better idea of the overall use case set so that scopes that have those as their strengths can be pointed out.

[EEVblog]

Then again, the OPs project goals make next to no sense at all so there is little use in suggesting anything. An oscilloscope is not a high precision instrument for measuring amplitudes anyway. If the OP wants to measure DAC steps accurately, then he/she needs to set the DAC to a specific output code (DC level) and use a >4.5 digit DMM to measure the DAC's output value.

The world will be a better place without people such as yourself who lean into providing 'advice' yet belittle projects at the same time - all before you even understand what is happening.

Well, In have been designing circuits professionally for decades and have used & owned more different oscilloscopes (from low end to very high end) compared to the average forum member. And yet up to my post the details you posted prevented me from making a useful suggestion to you. I prefer to stay on the safe side. Judging from how you are still jumping between various models based on the latest suggestions, I strongly suggest you make a list with pros and cons for various models and make a decission based on that. Try to make a comparison between the Tektronix TDS 2024B you have used before; what did you like and what didn't you like about it. Shared and individual channel controls can make a difference but the lower cost models suggested so far have shared controls where the TDS 2024B has individual channel controls. In the low cost segment GW Instek is one of the few brands that have individual channel controls (GDS-1054B is a very cheap 4 channel model with individual channel controls).

However, none of the models suggested so far is fanless. A requirement which should have been in your first post. Many people are replacing the fans in their oscilloscopes with lower noise models for better comfort (but likely voiding warranty). Rohde & Schwarz made fanless DSOs up to recently; look for HMO1000 series (for example: https://www.batronix.com/shop/rohde-schwarz/HMO1000.html). These likely can be found on the second hand market and at equipment dealers.

I don't care about how good you are at scopes with an attitude like yours. I don't need someone telling me to write down what I like & dislike about scopes & telling me how to make decisions. I have select posts for specific criteria. Just get lost - you aren't helpful.

If someones response on the forum isn't helpful then why not just ignore it?

[EEVblog]

I'll give you the details of what I'm trying to view in the scope and the actual scope so you can see if it'll work.
 
I wish to sample a 20,000Hz sine wave made up of 256 segments. An 8-bit DAC, unsmoothed.
I need to see each of the 256 digital segments as clearly as I can. Eg, the more squarey the better.

20,000Hz * 256 = 5,120,000Hz.

Since I'm wanting to view square waves, I am aware that its a game of 'how many upper harmonics of my fundamental can the scope see? enough to make it squarey?'.
I am aware that 100,000,000Hz is in the neighborhood of 19x my 5.1MHz fundamental.

Maybe what you want here is the ability to turn of SinX/x interpolation so you can see just the samples instead of a smooth "interpretation" of what's happening between the samples. 100MHz analog bandwith should be enough here I'd imagine.
EDIT: Just noticed you said 20KHz. In that case this isn't relevant. Any scope will show what you want, and you can overrange the vertical to help see details if needed.

[pepelevamp]

If someones response on the forum isn't helpful then why not just ignore it?

because bullshitters like that make life awful for newcomers for no good reason. and nobody likes the wankery. just too old for that shit, danny glover, etc.

but anyway, I think you're right re 100mhz being enough. I know my 'dac's amplitudes / codes are cool already so thats fine. I was concerned that 100mhz may be just low enough to shave off the edges of the square wave transitions & stop me being assured of my timing. yeah its a 5.1MHz square wave, but those transitions, right.

i have similar issues with the amplifier stage at the end of my signal chain - but its a lot easier figuring out which opamp to buy than a scope.