Which scope for (very) low freq signals ?

[guyd2]

Hello, my very first post here.

I am an E-musician, and I dabble a bit in analog electronics, mainly to create synthesizer modules et all.
Definitely not an engineer, but I do know the difference between a capacitor and a resistor (and a bit more).
I have no experience with microprocessors, AD/DA's, etc., and do not plan to get involved with that, mainly because I ain't no programmer either.
My scope (pun!) is restricted to op-amp applications, some CMOS logic, and anything that involves voltage control and audio. Thus, anything between DC and max 20kHz (plus sidebands/overtones/overshoots).

I'm in the market for a modern scope, since my old Rigol DS1052E is telling me "I've had enough, and I want to retire".
(it now takes forever to draw a 1Hz waveform at 1s sample rate, without a screen refresh; don't know why that came to be, but it's unworkable)

I've read quite a few posts here about scopes that I think might be of interest to me, but most discussions quickly veer off into mega-MHz territory and digital signal probing, and other high-end stuff which I reckon is of no use to me.
So, bandwidth is of no concern ~ 50MHz will do just fine I think.
Voltage range is important; I mostly work with -/+12V up to -/+18V supplies. That leaves out most USB scopes (of which I'm not a big fan).
Measuring/capturing very low frequencies is where most of my work is done ~ a 10min/cycle is not unusual. I couldn't find anything in this forum mentioning that...

Currently working on a clocking project where it would be nice to see 16 different pulse trains at once (divisions of 300Hz), though that would be a bonus.
Four channels would be nice (quadrature waveforms), but again, not an absolute must.
Mac OS compatibility (*) is a must, if only to be able to read off things via USB, or even a USB stick (the 1052 can't read my USB formatting anymore).
Most of my esteemed collegues in my niche-domain seem to work with a Rigol 1054, but this is older technology and I feel there must be something more modern and better nowadays.

My budget sits inbetween a wife-pleasing low-end (500-ish), and a I-better-prepare-a-nice-dinner-first ±1300-ish (€).

(*) I've read up on the Pico scopes, which seemed interesting, but their Mac implementation clearly leaves much to be desired.


Thank you for helping me out !
_Guy

[fourfathom]

Any modern digital scope should be suitable, but first, tell us more about the difficulties with your current scope.  It sounds like you have a setup problem.

For example, do you really have "1 sample per second" selected?  That *will* take minutes to complete a screen trace, and is absolutely not an appropriate setting for viewing a 1 Hz signal.  You want the sample-rate to be (roughly) ten times faster than the highest frequency component of the signal you are looking at.  With most scopes you will use a much faster sample rate.

Or do you have a "1 second sweep" enabled?  This is much different than "1 sample / second", and should give you screen updates close to one per second (and will show you one cycle of a 1 Hz signal).  If you are not getting fast screen refreshes, then perhaps your trigger is set incorrectly, or you have a "single sweep" mode enabled.

[rstofer]

I just took a 1 Hz sine wave from my Siglent SDG2082X and stuffed it in my Rigol DS1054Z and set the time/div at 200 ms.  Since there are 12 divisions on the horizontal axis, I get a screen sweep in 2.4 seconds so I have more than 2 full sine waves.

Since the screen is 2.4 seconds wide, it obviously takers 2.4 seconds to draw.  Nothing unexpected, that just the way it's supposed to work.

The Auto button did't do such a swell job of picking defaults.  It got V/div horribly wrong and the sine save looked square when clipped at the top and bottom of the screen.

In the end, I am getting 5 MSa/s using 12 M pts.  Exactly right!

In my case, I used a BNC<=>BNC cable so probe selection is 1x.

[DaJMasta]

I find roll mode is best for very low frequencies (don't forget to DC couple!), but what you're talking about is still well into the reasonable update rate <10ms/div sort of territory.  For audio work in particular, I'm always one to recommend a PC sound card (external, internal, otherwise) when possible because the dynamic range of their converter is so much higher than a scope and because they're often a free option - but I don't have a go-to scope emulator software, just spectrum analysis stuff (spectrum lab!)  If you're working with larger signals or faster stuff (like power line noise for DC rails or the occasional square wave with a nice sharp edge), it's not capable without the extra bandwidth and ranging options, but for a lot of line level or so work it can be a great, often free, tool.


If you're actually looking at 1 sample per second or that ballpark, (<0.5Hz visible signal) you don't need a scope, you need a multimeter that can graph or that has a data connection to something that will.  Still, a scope in roll mode will show you it.

A 1052E is solid but definitely shows its age, nearly any more current scope will feel a lot snappier and more modern, and there are quite a few discussions of what's available.  The DS1054Z and its variants, Siglent's 1104X-E or similar, or more expensive Keysight 1000X series or Rohde & Schwarz RTB scopes could all fit the bill for you.  Something with more bit depth (only the RTB in the ones I mentioned, but there are others) gives you more dynamic range and gets closer to what an audio system would actually see/output, but probably doesn't need to be a chief concern unless you're dealing with very small signals - it still comes at a bit of a price premium.  Search around for some discussions of entry level scopes and you should have more than a few options, and most of these offerings should have some sort of video available showing them in use, so you can get a bit of a feel for the UI and responsiveness, but at least compared to your current scope, any of these would be a notable improvement across the board.

[WattsThat]

Voltage range is important; I mostly work with -/+12V up to -/+18V supplies. That leaves out most USB scopes (of which I'm not a big fan).

Don’t understand this comment, of course a usb scope can display a +/-20 volt waveform. What does being usb have to do with vertical input range?

Currently working on a clocking project where it would be nice to see 16 different pulse trains at once (divisions of 300Hz), though that would be a bonus.

If those signals are analog, most scopes top out with four vertical channels. If the signals are digital in nature, we’ll then that’s a logic analyzer and 16 channels can be had.

[rstofer]

I'm in the market for a modern scope, since my old Rigol DS1052E is telling me "I've had enough, and I want to retire".
(it now takes forever to draw a 1Hz waveform at 1s sample rate, without a screen refresh; don't know why that came to be, but it's unworkable)

I'm not sure I follow a "1s sample rate" but if you're talking about 1 sec/div then it takes 12 seconds to draw the screen.  I would think you would want something like 200 ms/div which only takes 2.4 seconds to draw the screen and display a little more than 2 sine waves.

I've read quite a few posts here about scopes that I think might be of interest to me, but most discussions quickly veer off into mega-MHz territory and digital signal probing, and other high-end stuff which I reckon is of no use to me.
So, bandwidth is of no concern ~ 50MHz will do just fine I think.
Voltage range is important; I mostly work with -/+12V up to -/+18V supplies. That leaves out most USB scopes (of which I'm not a big fan).

The standard answer is going to be the Rigol DS1054Z or the newer Siglent SDS1104X-E.

Measuring/capturing very low frequencies is where most of my work is done ~ a 10min/cycle is not unusual. I couldn't find anything in this forum mentioning that...

The DS1054Z will go to 50s/div or 600 seconds across the screen which is JUST enough for 10 min/cycle.  10 min = 600 seconds and 600 seconds / 12 divisions -> 50s/div.

Currently working on a clocking project where it would be nice to see 16 different pulse trains at once (divisions of 300Hz), though that would be a bonus.
Four channels would be nice (quadrature waveforms), but again, not an absolute must.
Mac OS compatibility (*) is a must, if only to be able to read off things via USB, or even a USB stick (the 1052 can't read my USB formatting anymore).
Most of my esteemed collegues in my niche-domain seem to work with a Rigol 1054, but this is older technology and I feel there must be something more modern and better nowadays.

The Siglent is newer by a few years but Rigol has eliminated all the known bugs.  I'm not sure where Siglent stands and that's kind of important because I plan to gift my DS1054Z and buy the SDS1104X-E.  I'll look around on this forum for a 'bugs' list.

It's too bad you don't want to consider USB based devices.  The Digilent Analog Discovery will go to 100,000 hours/div and there are 10 divisions on the screen.  One minute per division is no big deal.

Not only does the AD2 have 2 scope channels it also has 2 arbitrary waveform generators and 16 digital channels that can be used as a logic analyzer.  It also does protocol decoding (I2C, SPI, etc) and has a raft of software defined tools.  It is my favorite tool even though I have the Rigol scope and Siglent AWG.  Those are great tools, the AD2 is handier.  There's something about a 27" scope display!

My budget sits inbetween a wife-pleasing low-end (500-ish), and a I-better-prepare-a-nice-dinner-first ±1300-ish (€).

Even the most expensive AD2 kit plus all known optional add-ons won't get the $500 (I think).  The "Ultimate..." kit is out of stock so I can't check the price but I'm pretty sure it is well under $500.  Exchange rate and import taxes are unknown to me but there is an office in Romania.

Too bad it's USB!  It runs on Mac, PC and Linux including the Raspberry Pi.  Here's something cool:  If you want to diddle around with the Pi GPIO (including SPI), you can write the code, connect the AD2, run the program, capture the signals and display them on a 27" monitor - all on the same machine.  Somehow I find that satisfying.

You can download the Waveforms software and play around because it implements a Demo device which will at least display some stuff on the screen.

There are 4 simple experiments starting at Reply 52 here:
https://www.eevblog.com/forum/testgear/starter-scope/50/

Duplicating these experiments on a scope is darn difficult (I believe 'impossible' but somebody will have ginned up a way to do them).

(*) I've read up on the Pico scopes, which seemed interesting, but their Mac implementation clearly leaves much to be desired.


Thank you for helping me out !
_Guy

[guyd2]

Thank you for the replies; they're all very helpful.

First, sorry for my 1 sample/sec hiccup. I meant time/div set to 1s.
So yes, that takes 12s to draw, as expected.
But I want to look at what happens during e.g. a 10 minute cycle. When I set the time/div to 50s (D1052Z max), nothing happens... or at least, that's what I thought... there's just the beginning of the waveform in the screen's center, which does not move at all. So I give up and move on to faster divisions, missing out on all of the information. Patience, apparently, is not my biggest virtue.
I've just ran a test at 50s/div, and can confirm it works.
So perhaps my question should be : isn't there any other & better way to do this without waiting hours for a waveform to display ? "Hours" because sometimes I'm dealing with even slower cycles (20m), which can (and will!) differ over different cycles. Also, that would steal away valuable time to check on other, faster things...
I thought of logging slow data (how?), and then dump that to my Mac where I could study the passage of a waveform over a very long time (hours). But since an earlier update of Mac OS, the Rigol has turned out to be completely incompatible. I can't even update its firmware.

I don't know what "rolling mode" is. Sorry for my ignorance.

The reason why I tend to shun USB devices, is that I sometimes deal with PSU's too. From what I understand, USB devices are often not protected against, say 36V, even to the point where I'd risk frying my laptop. And more often than not, their software are poor ports of PC to Mac (again, Pico. Looks stunning in its specs, but their Mac implementation is beyond abysmal).

I've seen the Analog Discovery mentioned here a few times, and I checked it out. There was some reason I dismissed it, though I forgot which reason. I'll check it out again, thanks.

My laptop is an old 17" (!) MacBook Pro. USB2 only, and FireWire. It's big & clumsy, and would take up a lot of space on my smallish workbench. It was a powerful [costly] beast back in 2011; now it's completely outdated (and won't run newer Mac OSses). Would that suffice to run AD2 ?

---
A friend (a real engineer) bought a lower-end Rohde recently, and I was amazed looking at its crisp touch display, its snappiness, and endless possibilities (though mostly over my head or beyond my needs). In comparison my Rigol looks & feels like Pong on an Atari 2600.
I dont' see Rohde mentioned often here ?
---

So, is the conclusion then that *any* newer scope in the low $ range would satisfy my needs, or perhaps even that I don't need a new scope at all (and/or should look again at the USB options) ?

cheers,
_g

[fourfathom]

I don't know what "rolling mode" is. Sorry for my ignorance.

I just looked at the manual for your scope, and it has a "Roll Mode" as well as a "Slow Scan" mode, either of which should give incremental updates after the trigger -- you won't have to wait for the entire capture period to complete.  Roll mode doesn't even have a trigger, it just displays the signals as they come in, newest samples to the right, oldest samples to the left.

[tautech]

Near the top end of your budget is SDS2104X Plus that has a thread on the forum, check it out.

Some scopes offer 2 types of Roll mode.  Auto Roll (below a certain timebase setting usually ~50ms/div) take a mo for the waveform to display until the display buffer fills while in dedicated Roll mode the display starts immediately filling however only at the speed of the timebase setting.

[guyd2]

- Need to find the manual for the D1052... 
  (now I feel guilty for not studying it better, 11 years-or-so ago ~ darn impatience)

- The SDS2104X Plus looked tempting indeed (but perhaps a bit overkill for me). I read some of the thread, though not all 45 pages.

Cheers,
_g

[shakalnokturn]

For your slowest business and depending on the time resolution you need a DMM with logging function or PC connection could do the trick.

As for a basic setup for 16 channel PC based logic analysis that can be got for the price of a pack of beer.

[rstofer]

The AD2 has a data logger gadget as well.  The data can be exported to the clipboard, with or without headers, and imported into a spreadsheet.  I tried it on Linux with Libre Office.  The logger works with the 2 scope channels.

There is also the 16 channel digital capability which includes a Logic Analyzer function.  There are USB limitations on the external recording of samples but there is a feature-rich internal buffering system which can export data to the clipboard and onward to <whatever eats clipboard data>.

It is worth playing with the software and Demo mode to see how this works.  I haven't used either feature.

[xani]

- The SDS2104X Plus looked tempting indeed (but perhaps a bit overkill for me). I read some of the thread, though not all 45 pages.

It is probably massive overkill. SDS1104x-e have all you need. Like, bigger screen is cool and all but you probably can get more useful tools for the price difference

It is (I think?) lowest series that gives you access to Sigilent's bode plot app. It basically draws the frequency characteristic (frequency vs signal level/phase) of the device, which can be very useful for building filters and checking performance of analog circuits. It does require either buying the signal generator option (for that model it comes as separate box talking with scope over USB), or owning one of Sigilent's signal generators (I own SDG1025 and it works just fine with it, altho a lot of relay clicking). Roll mode goes to 100s/div

It also have MSO option (extra 16 digital channels), altho if you don't need anything fancy any separate logic analyzer will do


Please, do check up the Analog Discovery 2 Waveforms app demo mode at least.

The hardware itself is amazing deal for the price, you get 2 analog channels with 14 bit ADCs (most scopes have 8 to 10 bits, altho more fine grained input ranges), 2 signal gen outputs and a bunch of other features. And scripting, if you want to make some automated test jigs.

Voltage range is important; I mostly work with -/+12V up to -/+18V supplies. That leaves out most USB scopes (of which I'm not a big fan).

Most scope probes have 1/10x switch, just use it in 10x mode. The usual use case of 10x probe is for higher bandwidth (the rated bandwidth of scope probes is for the 10x mode)

[guyd2]

The Siglent SDS1104x-e looks interesting indeed. Though adding the MSO and Waveform Generator options quickly adds up and almost brings it up to the next ($) level, where these features might be standard. Browsing through its user manual (17 pages of "warnings" ??) does make me feel like I'm looking at my old Rigol, just slightly better... And once more, no mentioning of Mac compatibility (specifically about the USB storage device stuff). The world of scopes seems very PC-centric; as if Macs don't exist. Being a graphic designer & photographer by profession, Mac compatibility is a rather important decisive factor for me.

Which makes, amongst other things, the AD 2 looking more and more like the best solution for me.
It does have a lot of features which are of no interest to me, but being software-based I can simply ignore these since they didn't cost me extra money anyway. It's not available right now -- only for "Academic orders" (understandably) -- until the 28th of May.
I've watched the Waveforms app demos, and yes, that has a lot of appeal to me.

Thank you all for the input and advice !

cheers,
_g

[MasterBuilder]

I wouldn't worry about Mac compatability on the Siglent as controlling these scopes from a computer is fiddly at best, only relevant if u intend doing automation and writing scripts and things.
If interested in the waveform generator I would purchase a separate waveform generator (or Analog discovery 2 can do this well) and the scope.

Also the Analog discovery 2 is great and I'd avoid the Pico products.

[Fungus]

I don't know what "rolling mode" is. Sorry for my ignorance.

The entire screen scrolls sideways and new samples are added on the right.

I just looked at the manual for your scope, and it has a "Roll Mode" as well as a "Slow Scan" mode, either of which should give incremental updates after the trigger -- you won't have to wait for the entire capture period to complete.  Roll mode doesn't even have a trigger, it just displays the signals as they come in, newest samples to the right, oldest samples to the left.

Yep. The DS1052E should be able to do it perfectly with the right setup.

[John B]

Sounds like there are multiple different applications and multiple different tools required here. I'd say forget a bench scope for recording long periods of data, unless something can be streamed through a LAN port. Even if you could parse through 10mins of data on a tiny scope screen, would you want to? I'd use a USB scope

[rsjsouza]

Given your requirements, I agree with others and suspect the AD2 is the better solution for you - as you said yourself, just see if the software runs on the older OSes (Apple changed so much on the USB system on the latest releases...)

Regarding the DS1052, from what I understand you are waiting a long time for the waveform to start showing in the middle of the screen, right? If so, can you use the horizontal position and move the trigger point to the left of the screen? I did lots of roll and slow captures with my old DS1102E (same family) and it worked really well.

[tautech]

The Siglent SDS1104x-e looks interesting indeed. Though adding the MSO and Waveform Generator options quickly adds up and almost brings it up to the next ($) level, where these features might be standard. Browsing through its user manual (17 pages of "warnings" ??) does make me feel like I'm looking at my old Rigol, just slightly better... And once more, no mentioning of Mac compatibility (specifically about the USB storage device stuff). The world of scopes seems very PC-centric; as if Macs don't exist. Being a graphic designer & photographer by profession, Mac compatibility is a rather important decisive factor for me.

Depends entirely on just what you need to do.
FYI, adding MSO to any scope capable of it is never cheap.

The 4ch X-E's webrowser is a fast and powerful tool totally accessible from any computer with a browser installed and a LAN or WiFi connection.
Have a look at the video here:
https://siglentna.com/video/x-e-4-channel-web-browser-update-this-thing-is-fast/
 

[vk6zgo]

Back in the day, for really slow rate testing, the instrument of choice was a chart recorder.
These would, using an electromechanical  system, draw the voltage changes on a continuous tape.
You read them by tearing off the section you wanted, & examining it visually.

They were still making similar devices a few years ago, but what is used these days, I don't know.

[fourfathom]

Back in the day, for really slow rate testing, the instrument of choice was a chart recorder.
These would, using an electromechanical  system, draw the voltage changes on a continuous tape.
You read them by tearing off the section you wanted, & examining it visually.

They were still making similar devices a few years ago, but what is used these days, I don't know.

When I was a tech (about 40 years ago) I built a 16-channel analog multiplexer that fed the "Rustrak" strip-chart recorder: two index channels (ground and a positive voltage reference), and 14 measurement channels.  It cycled through the channels slowly enough that we could count from the index channels to identify the measurement channels.  We used it for battery load testing during product development.  It was a simple design using 4000-series CMOS parts, but it served our needs very well.

[Fungus]

I'll second the AD2.

Voltage range is important; I mostly work with -/+12V up to -/+18V supplies. That leaves out most USB scopes (of which I'm not a big fan).

Two resistors will divide a voltage. Most 'scope probes have a divide-by-ten switch (although you might want to get one that's fixed at 10x)

Currently working on a clocking project where it would be nice to see 16 different pulse trains at once (divisions of 300Hz), though that would be a bonus.

If you want to look at a lot of digital channels then the AD2 costs less than the price of just the logic probes for a DSO.

Most of my esteemed collegues in my niche-domain seem to work with a Rigol 1054, but this is older technology and I feel there must be something more modern and better nowadays.

Older != obsolete in this world. Things change really slowly here, three years is nothing.

[rstofer]

For the Logic Analyzer function, if the 16 channels of the AD2 aren't enough or perhaps there is a desire to generate 16 signals and track 16 other channels, maybe the Digilent Digital Discovery is appropriate:

https://store.digilentinc.com/digital-discovery-portable-usb-logic-analyzer-and-digital-pattern-generator/

Note that the device can sample 8 channels at 800 MSa/s.  That's pretty darn fast!
Sixteen channels at 400 MSa/s and all 32 channels at 200 MSa/s.  Still pretty decent!

The high speed probes are required for sample rates of 200 MSa/s and higher.

Yes, it is a LOT more expensive than the eBay specials.

And, yes, I have one.  I don't use it a lot because I'm not working on anything right now but I'll get around to it sooner or later.  Mostly, I just use the AD2 because it is sitting right next to my computer.

[rstofer]

Most of my esteemed collegues in my niche-domain seem to work with a Rigol 1054, but this is older technology and I feel there must be something more modern and better nowadays.

Older != obsolete in this world. Things change really slowly here, three years is nothing.

It took the first couple of years to iron out the bugs in the firmware of the DS1054Z.  Every new scope has bugs but the question is:  How long to root them out?  It took a few iterations...

The Siglents also have (or had) bugs in the initial firmware.  I haven't followed along so I don't know where it stands today.

These bugs are not usually encountered by the average user and don't really affect things except at the margins.  The Rigol spelling error was the last thing to get updated as I recall.  It was kind of a 'badge' that was an inside joke for a while.

[coppercone2]

you might be interested in the very high bit count ADC's (32) that are made for seismic exploration purposes. You can't really use the extra bits conventionally (I understand its more useful for DSP or stats)