Author Topic: My first oscilloscope (Read 7203 times)

osteichthyes · « **on:** June 07, 2018, 11:04:39 am »

Hello, I know I've seen a zillion posts similar to this and I've seen a few different pieces of advice. 1) get the analog discovery. 2) get an entry level USB oscilloscope like an Owon. 3) buy used.

I'm leaning towards getting a used scope. So, here are my questions: what should I look for/avoid in an ebay listing? I've got plenty of DMMs, and I love Fluke stuff. I love the form factor for their scopes. Are Fluke scopes as good as their DMMs? What about the 93? Honestly, my needs are pretty basic, I'll be mostly doing audio stuff.

Are there other questions I should be asking that I'm missing?

Thanks!

tautech · « **Reply #1 on:** June 07, 2018, 11:08:28 am »

Welcome to the forum.

Your location and budget will help with the right (for you) advise.

Discotech · « **Reply #2 on:** June 07, 2018, 01:35:41 pm »

From what I've researched, the most important thing is to look for 2nd hand scopes with pictures of a working display

Dave did a good guide on buying 2nd hand here

rstofer · « **Reply #3 on:** June 07, 2018, 02:46:18 pm »

eBay is a risk. You might get something that works pretty well but you might not. You might have the skills to fix it, you might not. What if you need another scope to fix it?

Budget is the discriminator. How much do you want to spend? The next question: What do you want to see? 'Audio' only takes about a MHz of bandwidth so just about any scope can handle it. I wouldn't even think about a scope with less than 50 MHz of bandwidth on the off chance I might want to move on to microcontrollers later on.

The cheapest possible setup is a PC sound card. You'll have to do some Googling. I wouldn't use my best, or only, PC for this.

I bought a uses Tek 485 about 12 years ago on eBay for about $200. It still works well but I did buy a Rigol DS1054Z for the DSO capabilities. There are similar 485s on eBay from about $250 up.

I'm a huge fan of the Analog Discovery 2 but it's pricey compared to some low end used scope. The thing is, you wind up with a lab in a box. Dual channel scope, dual channel arbitrary waveform generator, 16 channel logic analyzer, digital IO with patterns. That's the simple stuff... Then there is the Network tool which produces Bode' plots of frequency/phase for various circuits. Or the FFT gadget. The dual channel power supply, although limited in voltage and current, is just right for powering breadboard projects.

By the time you buy a useful AD2 kit, it's getting kind of pricey. But it, and a laptop, easily fit in a backpack. You can work anywhere.

Philosophically, I like more channels. The 4 channels of the Rigol were more compelling than the DSO features. My 485 has only 2 channels and I wanted to be able to see all 4 signals of the SPI bus.

Probably the most compelling feature of the DSO is the single shot mode. You capture the trace and look at it as long as you want.

Today, I would be looking at the new Siglent offerings. I have my eye on a SDS 1204X-E for about $800. Four channels, 200 MHz and plenty of capability makes it a pretty nice scope.

osteichthyes · « **Reply #4 on:** June 07, 2018, 04:28:46 pm »

My budget is not huge. Under $200, certainly. I'm in the US. And, relevant to the AD2, I am a student. Though they keep rejecting my student application because I'm not using it for a class.

Thanks for all the info, that video looks helpful.

By audio, yes even a few kHz would probably suffice. That said, I do build sensors for work. I've not yet needed a scope for that, but it's not outside the realm of possibility that I could.

I've considered a USB scope on a raspberry pi wirh an old monitor as sort of a dedicated setup. It seems like I'd need to isolate it if I'm using higher voltages, right? Regarding the cheaper usb offerings, it seems the Owon is superior to the others, but offers no linux support. I do not have any windows computers any longer.

Thanks for all the advice.

Old Printer · « **Reply #5 on:** June 07, 2018, 05:08:52 pm »

rstofer pretty well nails it. You are allowed to just "want: a scope, maybe two or three:) If you really get interested in electronics you will probably wind up with several. I have a couple old Tek's and an Analog Discovery. I bought the AD last year and they are pricy, but by watching ebay I found a good original version of the AD for $55, but $150 is more average. I like it because I am a noob and it can do most anything, including digital, so it is a good learning tool. The original AD is 98% as good as the new one. The old analog scopes are fun and I have been lucky, but I wince every time I turn it on waiting for a cap to go. Here is a quick vid about analog scopes & tube amps.
BTW, the Analog Discovery will not work with the RaspberryPi, but I have heard it does work with the BeagleBone. Some sort of USB problems.

rstofer · « **Reply #6 on:** June 07, 2018, 05:29:45 pm »

There are plenty of those Tek 2205 scopes like the one in the video available on eBay and they are generally in your price range. A lot of scopes seem to come with free shipping and this can be a really big deal. Watch for weasel words in the description, make sure the seller says 'it works' and look for those that are refurbished or recently calibrated. They're out there...

Isolating a scope is an advanced topic, search around here for other discussions. If USB, you probably want to isolate the USB cable and there are devices for this. They don't run at the higher data rates and I don't know how well they might work or if they work at all on something like a scope. I guess I would also have some concerns if the scope was connected to my LAN.

That's among the considerations with the Analog Discovery 2 - I have to guarantee the voltages are reasonable and, if necessary, I can use the BNC adapter with x10 probes. But I lose the differential inputs if I use the adapter and this is a really big deal for testing some kinds of circuits. Differential inputs are uncommon on all commercial scopes because the BNC connector must be grounded. That's why people float their scopes and why it is an advanced topic. Differential probes (Dave sells one) solve the problem but they aren't cheap. If I had to float the scope, I would skip that and buy a differential probe. It's safer!

Use x10, x100 and even x1000 probes if you must on working at higher voltages. They're all over eBay... I work at 12V or less so I don't deal with isolation. Fifteen volts is a really big day. And all from low current wall warts or bench supplies with current limiting.

As to probes, use x10 for just about everything, x1 probes don't really help. x100 probably aren't necessary until the voltage gets higher.

In your position, I would wait until I could afford the Rigol DS1054Z or the Siglent 1202X-E. The Rigol is now down to $349 and the dual channel 200 MHz Siglent is $379. That new Siglent seems to be amazing. Sure, it's only 2 channels but that was pretty much the standard for MANY years.

The thing about scopes is that they last forever. It's worth doing it right the first time rather than doing it twice.
https://store.siglentamerica.com/product-category/digital-oscilloscope/sds1000x-e-series/

rstofer · « **Reply #7 on:** June 07, 2018, 05:32:09 pm »

And do be aware that most of the eBay scopes don't come with probes and, for some reason, they don't have power cords either. I think the sellers are parting them out.

osteichthyes · « **Reply #8 on:** June 07, 2018, 08:01:39 pm »

Wow. Those new scopes are not much more expensive and seem excellent. Maybe that is my best bet. Out of curiosity, are there any more portable scopes that you'd recommend? I mentioned those used Flukes. Is there anything closer to that form factor?

lordvader88 · « **Reply #9 on:** June 07, 2018, 08:04:39 pm »

A bench is great too, but don't rule out a cheap $20 DSO138 from ebay. The are low 200kHz bandwidth, but the are powered off 9V, and so aren't mains-earth referenced, and so u can probe anything without worries. They are handheld and plenty good enough for lot's of stuff, u just have to know their limitations.

I have 2 working tektronix bench scopes, but I can't use them on the hotside of anything from main's power.

rstofer · « **Reply #10 on:** June 08, 2018, 02:40:18 am »

If you want to talk about specific pieces of test equipment, maybe you should post a somewhat different question in the Test Equipment forum. Reword it so it doesn't look like a duplicate post.

There aren't all that many handheld scopes around. It's kind of a niche deal for industrial electricians - think radio bridge crane controls where 4 lift units are slaved to move the fuselage of a DC-10 down the assembly line. Been there, done that... We didn't have those nice Fluke scopes but they sure would have been handy - way up there!

What is probably better is a bench scope with as large a screen as you can get. Then with a built in web server, you can read the scope on a 27" display.

See Reply 12 here:

https://www.eevblog.com/forum/testgear/here_s-how-bad-siglent_s-(sds1104x-e)-gui-is/

Read the thread before considering the title. Sometimes people get confused...

Old Printer · « **Reply #11 on:** June 08, 2018, 12:15:18 pm »

If you are considering the older Analog Discovery, the only functional difference is an added variable supply with a 5 volt max. The AD1 can actually do the same thing from the wavegen outputs, though you do tie up one of the outputs in the process. The case of course has been redesigned to be eye catchy, but in an operational sense they are pretty much the same unit. Add an inexpensive power supply and you are back to square one. I bought a couple of the older HP 6216A single output power supply's on ebay and I have a much more functional setup than using the AD2's built in supply.

rstofer · « **Reply #12 on:** June 08, 2018, 02:55:49 pm »

Quote from: Old Printer on June 08, 2018, 12:15:18 pm

If you are considering the older Analog Discovery, the only functional difference is an added variable supply with a 5 volt max.

Actually, the AD2 power supply can make use of an external wall wart to drive more power output than you can get with the USB connection. The original AD is very limited on current output while the AD2 can go quite a bit higher

Quote

Two programmable power supplies (0…+5V , 0…-5V). The maximum available output current and power depend on the Analog Discovery 2 powering choice:
250mW max for each supply or 500mW total when powered through USB
2.1W max for each supply when powered by an auxiliary supply
700mA maximum current for each supply

The original Analog Discovery was limited to 50 mA from each supply. This USB limit is where the 250 mW number comes from above. Being able to get to 2.1W is pretty nice!

mtdoc · « **Reply #13 on:** June 08, 2018, 03:08:12 pm »

Once you’re adding an external wall wart to the AD2, you’ve lost any added value IMO. A very cheap and small regulated supply could just as easily be added that would provide much wider voltage and current capability.

rsjsouza · « **Reply #14 on:** June 08, 2018, 04:37:55 pm »

Some folks around here are very fond of Picoscopes - apparently their software is quite good.

At a price within your range, and suitable for analog audio and some limited digital debugging, are two eBay listings:
Picoscope 2202 (2 channels, 2MHz@20MSPS) - new with warranty
Picoscope 2203 (2 channels, 5MHz@40MSPS) - used with warranty

Old Printer · « **Reply #15 on:** June 08, 2018, 05:01:13 pm »

Quote from: rstofer on June 08, 2018, 02:55:49 pm

Quote from: Old Printer on June 08, 2018, 12:15:18 pm
If you are considering the older Analog Discovery, the only functional difference is an added variable supply with a 5 volt max.

Actually, the AD2 power supply can make use of an external wall wart to drive more power output than you can get with the USB connection. The original AD is very limited on current output while the AD2 can go quite a bit higher

Quote
Two programmable power supplies (0…+5V , 0…-5V). The maximum available output current and power depend on the Analog Discovery 2 powering choice:
250mW max for each supply or 500mW total when powered through USB
2.1W max for each supply when powered by an auxiliary supply
700mA maximum current for each supply

The original Analog Discovery was limited to 50 mA from each supply. This USB limit is where the 250 mW number comes from above. Being able to get to 2.1W is pretty nice!

rstofer, quite true on both accounts, but the price range in the used market for the original AD can vary quite a bit, while even used AD2's generally run $250 & above. Digilent sold a ton of the AD1's to students at the $99 price and they are much more likely to show up at a good price. Particularly if the owner has graduated and not kept up with current pricing.

mtdoc · « **Reply #16 on:** June 08, 2018, 06:11:01 pm »

Quote from: Old Printer on June 08, 2018, 05:01:13 pm

rstofer, quite true on both accounts, but the price range in the used market for the original AD can vary quite a bit, while even used AD2's generally run $250 & above. Digilent sold a ton of the AD1's to students at the $99 price and they are much more likely to show up at a good price. Particularly if the owner has graduated and not kept up with current pricing.

Good point. IMO the AD2 which came out after NI acquired Digilent - is simply a repackaged AD1 with a next to worthless "improved" power supply sold at a much higher price. I would not pay anything extra to get an AD2 versus an AD1 (which is a wonderful tool. I love mine!).

As I mentioned above, if you add a cheap linear supply (for example one of these for $5.50 0r build one for $2 in parts) to the wall wart you'd have to add to the AD2 anyways, you'll have a much more powerful, small, regulated linear supply to accompany your AD1.

rstofer · « **Reply #17 on:** June 08, 2018, 08:31:08 pm »

I'm not debating the utility of the original AD, I have one. I was a pretty early adopter. I do think the enhanced power supply of the AD2 is a useful upgrade but if the discussion is about USED ADs then, sure, the original will do the job.

Frankly, I always get nervous connecting USB things to my PC. I do have a couple of junk PCs for this kind of thing but, more likely than not, I first get started on one of my more important machines. Similarly, I would get a little nervous about powering a project from the AD whether it was a version 2 with wall wart attached or not.

The absolute last thing I want to see is magic smoke coming out of my high dollar AD2!

I use wall warts to provide things like 5V to a board. I have a bunch of 5V 2A warts that came with various FPGA boards so I don't have any problem finding one.

A brief check on eBay shows NO used version 1's and just a few version 2's and some of those are selling for more than factory. Of course, some are marked as 'or best offer' but I don't know what that means in terms of a reserve price. My searching 'foo' doesn't work in eBay. I get a few ADs and then pages and pages of watches and everything else under the sun including such helpful items as iPhone power cables. If somebody has a better search string than 'analog discovery', I'm happy to learn!

I would think that if someone were hanging around a college, these things would be a lot easier to find. I wonder if they would wind up in the book store as 'used'. Used textbooks wind up there...

osteichthyes · « **Reply #18 on:** June 08, 2018, 09:19:31 pm »

We have a place used stuff ends up. In my years here, I've occasionally done searches in that store. Once, years ago, an ancient looking scope popped up, but I wasn't looking then.

After all of the advice, I'm leaning towards either going for a used analog scope for the time being, or saving my pennies for the Siglent. I did notice that the Siglent doesn't support Linux. But, given that it has a screen, it seems less likely that I'd need/want to use a computer with it anyway. The 4 channel Siglent scopes have a web interface, but I'm really not sure that I'd use it.

tautech · « **Reply #19 on:** June 08, 2018, 09:46:17 pm »

Quote from: osteichthyes on June 08, 2018, 09:19:31 pm

We have a place used stuff ends up. In my years here, I've occasionally done searches in that store. Once, years ago, an ancient looking scope popped up, but I wasn't looking then.

After all of the advice, I'm leaning towards either going for a used analog scope for the time being, or saving my pennies for the Siglent. I did notice that the Siglent doesn't support Linux. But, given that it has a screen, it seems less likely that I'd need/want to use a computer with it anyway. The 4 channel Siglent scopes have a web interface, but I'm really not sure that I'd use it.

Some further study for you:
https://www.siglentamerica.com/video/x-e-4-channel-web-browser-update-this-thing-is-fast/

The webserver has been enhanced form the earlier factory version resulting from the work done by lundmar here:
https://www.eevblog.com/forum/testgear/open-source-lxi-tools-and-liblxi-v1-0-released-for-gnulinux/

If you want to ever get info from it, regardless of the PC OS you can use the websever and the SCPI commands in the webserver interface.

osteichthyes · « **Reply #20 on:** June 09, 2018, 12:13:40 am »

That is only on the 4ch version, right?

There's no way to interface with the 2 channel scopes from Linux, right?

tautech · « **Reply #21 on:** June 09, 2018, 01:10:10 am »

Quote from: osteichthyes on June 09, 2018, 12:13:40 am

That is only on the 4ch version, right?

There's no way to interface with the 2 channel scopes from Linux, right?

Yes, the LXI tools are especially for this.
Sure there's no webserver in the SDS1202X-E but the utility that lundmar built should interface directly with the scope for SCPI commands at least.

osteichthyes · « **Reply #22 on:** June 09, 2018, 02:25:57 am »

It seems like there might be some student discounts, so maybe I can make this all work. Thanks all for the advice and guidance, I really appreciate it.

tsman · « **Reply #23 on:** June 09, 2018, 02:55:53 pm »

Quote from: osteichthyes on June 07, 2018, 11:04:39 am

1) get the analog discovery.

The Analog Devices ADALM2000 is basically a cheaper $99 redesign of the Analog Discovery 2. It even has the same pinout. The main differences are that it uses its own Scopy software and the ADC/DAC is only 12 bit instead of the 14 bit in the AD2.

One neat feature is that it runs Linux inside and supports plugging in a USB Ethernet or WiFi dongle so can operate away from a PC.

It has only just launched though so it is hard to get and firmware + software is fairly new still. There are far more tutorials and videos for the Digilent Waveforms software that the AD2 uses though.

rstofer · « **Reply #24 on:** June 09, 2018, 09:09:56 pm »

I think that AD gadget is vaporware. I went on line to the AD website and tried to order one and all I got was 'Contact AD'. None of the normal distributors show any stock. It would be fun to compare the products but, in the end, the software is more important than the gadget. I want to use the tool, not just enjoy a lower price.


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Author Topic: My first oscilloscope (Read 7203 times)

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