Scope for beginner - Page 1
Forum section: electronics / beginners

author: mecanico
author_rank: Contributor
timestamp: January 04, 2016, 10:40:04 pm
content: Hi folks,I'm new to eletronics and I built a system with a PIC18f and an encoder. It happens that when I speed up the encoder, I get faulty reads on the lcd. Therefore I would like to buy a cheap oscilloscope to start debugging and get into eletronics. I read a thread about hantek 6022be, and some people say that it is bad, others that it will fill the needs, and even that there are people developing software for it. What do you think about this? Do you know any cheap scope that is better than this?Greetings

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 05, 2016, 12:51:15 am
content: Almost any oscilloscope is better than no oscilloscope at all.Yes, it will probably fill your immediate needs. But if you are going to stay in electronics as a hobby or profession, you will quickly want something better.

author: Gyro
author_rank: Super Contributor
timestamp: January 05, 2016, 11:37:55 am
content: If you can squeeze just a little more, the Owon VDS1022 seems to have come right down in price recently and is vastly superior to the 6022be.https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-%28versus-the-hantek-6022be%29/Edit: Other than that, the usual recommendation is the Rigol ds1054z bench scope, but thats a few hundred $ (well spent).

author: natbuk
author_rank: Contributor
timestamp: January 05, 2016, 01:06:06 pm
content: I'd vote for the Rigol unit also. Although you might want something faster in the future, for 95% of stuff, that little scope will do the job for you and will probably still be useful in many years to come, even if you one day buy a faster one.Regarding your encoder getting dodgy when you speed it up, a couple of things to consider:1) are you sampling the pins in some kind of polling-loop? (i.e. some bit in your code which keeps checking if the pins have changed state?) If so, this might be too slow, or may have times when polling is delayed due to other operations. Consider either polling in a timing interrupt, or if you can, use interrupt-on-change for those pins2) If it's a rotary encoder, to get the best performance, you need to carefully consider the switch-bounce that happens during transitions, and how your code interprets what an increment/decrement condition is. In general, you should look for a two-stage pattern, not just that one pin has changed state. When I've made these types of things in the past, I wrote them as a state machine in software, so at any given state, what's the possible next-states. And only when you transition through TWO states, can you really consider it an increment or decrement - otherwise, you can end up trying to follow a switch bounce. To test if you really did this properly, set up a number that will increment/decrement that you can read somehow (either debugger, or your display or similar), then grab the knob (with it securely fixed!), noting your 'starting position' and violently twist it back and fourth for a while. When you return the knob to the starting position, the number should be back to the starting number (usually zero). It's surprising how much kit/commercial products don't do this - and slowly the number/display shifts one way or another - sometimes called 'knob creep'.

author: Seekonk
author_rank: Super Contributor
timestamp: January 05, 2016, 03:07:44 pm
content: A $60 scope is easy to take cheap shots at. Considering you get two scope probeswith, the scope is only about $35. A customer bought me one of these for a projectthat never went anywhere. I happen to think it is an amazing piece of electronics for the money. You get two channels, ability to store an image, actual data points for that signal, frequency counter, time interval measurement, differential voltage measurement, and portability. It is the easy tale along instrument to document an issue at a customers site. The issues it has are no greater than a beginner would have with a $5,000 scope. I could only dream of having something half this good when I started out. While the open software is an amazing effort, it ran out of steam and is not ready for prime time. Most times I prefer to use the factory software. This scope and a free Harbor Freight meter and you are good to go. Lots of nice equipment doesn't make up for a lack of fundamentals.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 05, 2016, 07:04:31 pm
content: So when you take the Hantek scope along to your customer's site, do you use his computer or yours? Do you balance the scope, or your laptop, in your lap, or both? How much does the scope + laptop combo weigh, and does it have a carrying handle?Just curious, that's all.

author: Kolovrat88
author_rank: Newbie
timestamp: January 05, 2016, 07:32:39 pm
content: Few years ago the default choice was Rigol DS1052E and it's still a good scope nowdays.But if I wanted to get my first scope now I'd go for a Rigol 1054Z. I think it's amazing how good scope you can get for little money.Don't bother with those USB scopes, real knobs are much easier to work with.

author: mecanico
author_rank: Contributor
timestamp: January 06, 2016, 10:11:18 pm
content: HelloI didn't know that owon. Where can I find it in Europe for a good price?It is better than the hantek right?

author: Gyro
author_rank: Super Contributor
timestamp: January 06, 2016, 11:02:00 pm
content: If your budget is really limited (<100 euro) then it's far better than the Hantek, better, as in:- 25MHz rather than 20MHz- 100Msps (each channel) vs 48Msps- Proper hardware triggering in the unit vs very basic USB streamer and triggering done in PC S/W.- Decent H/W and S/W (ie, it works), decent UI with no noticeable bugs.Hopefully you have read the teardown thread by now.Ebay from China seems to be the best bet (presumably this is where you were looking for the Hantek) the cheapest I have seen is this one (I have no association):http://www.ebay.co.uk/itm/OWON-VDS1022-USB-25MHz-100MS-s-USB-PC-Digital-Storage-Portable-Oscilloscope-/351588937562?hash=item51dc556f5a:g:w5QAAOxygPtSt-XoThere are several other listings, your best option is do a search for VDS1022 from your own country's ebay.Note: There is also a VDS1022I variant which has USB isolation (probe ground isolated from USB ground) which costs more.I maybe should mention that the only other real option in this price range is to look for a second hand Analogue scope. Much less useful for PICs and encoders though.EDIT: There are some ebay sellers listed in Germany but of course the price is significantly higher.

author: daybyter
author_rank: Frequent Contributor
timestamp: January 07, 2016, 01:21:24 am
content: What samplerate do you need? Maybe a 10$ scope would do the job? 2 MHz stm32 scope:http://www.stm32duino.com/viewtopic.php?t=107

author: obiwanjacobi
author_rank: Super Contributor
timestamp: January 07, 2016, 07:48:59 am
content: Sure you don't need a logic analyzer? I have an old analog 20MHz scope (second hand $50,=) and a logic analyzer ($8,= on ebay) and have been able to find and fix all problems in my hobby projects (mostly MCUs and analog audio).

author: Galenbo
author_rank: Super Contributor
timestamp: January 07, 2016, 08:18:09 am
content: Quote from: mecanico on January 04, 2016, 10:40:04 pmIf you only want to look at 5v signals for the moment, why not really race to the bottom and build a PIC18f "scope"?Save as much as you can for a real starter device, price range 400 euro.

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 12:29:35 pm
content: A good point, a cheap 8 bit logic analyser (with Sigrok!) is so cheap at <$10 that it's pretty much a 'throw one in anyway' for protocol decoding etc.I actually bought one of those cheap JYE DSO138 1Msps scopes for the hell of it at Christmas. With on-screen readouts it's actually pretty good for the incredibly low price but in the same way as a <$10 DMM is ie. something that you can kick around the bench, float on a signal and generally sniff around low frequency stuff on the move. I has limitations on single trace triggering above 50us/div and below 50ms/div (for some reason) and I doubt if it would be a good choice for capturing mainly digital stuff. A bit more than a toy...but not by much.The Analog Discovery is a good choice - assuming that the OP can get the Academic discount, otherwise it is in a different price bracket.Budget-wise, all we know at the moment is, based on his strong interest in the basic Hantek 6022be and not biting on the several Rigol suggestions the OP has a very limited budget.@mecanico: It really would be helpful to know what your budget is, and also whether you are still in formal education (for the academic discount).

author: macboy
author_rank: Super Contributor
timestamp: January 07, 2016, 04:24:39 pm
content: Quote from: natbuk on January 05, 2016, 01:06:06 pmI already have a couple of faster ones, but I want to add the Rigol to the mix. I want the Rigol for the feature set: deep memory (at least compared to what I have), serial decoding, capture of waveforms to PC, etc. There are real uses for a fast analog scope, and other uses for feature rich slower digital scopes. You can easily have both on your bench for much less than $1000. And then there are fast, feature rich digital scopes that cost as much as a nice car.I also strongly recommend a cheap CY7C68013A based USB Logic Analyzer (<$10) combined with free sigrok software. This can be very useful for debugging microcontrollers, and the price is no restriction.

author: TinkerFan
author_rank: Regular Contributor
timestamp: January 07, 2016, 05:53:33 pm
content: I personally use an old Analog Scope with delayed Timebase, which is really helpful when working with digital signals. It is and 100MHz PM3065 and I paid around 200€ (approx 220$), but you can get normal analog scopes much cheaper off ebay.My friend uses an Hantek 6022BL and he is really happy with it, but he is more into digital stuff, where a cheap logic analyzer becomes really handy. But he doesen't really care about performance and I noticed that its response time is not the best. The logic analyzer is the main benefit of that thing. You usually have to pay a lot more for a scope with a logic analyzer and FFT(although that seems to be almost standard). If you do not mind a PC-Based scope and you do not want to pay more than 100$ that is probably not a bad choice.

author: mecanico
author_rank: Contributor
timestamp: January 07, 2016, 06:29:34 pm
content: Hello folks,So many answers, wow, you guys are awesome.I'm starting to move with eletronics, and what I want is to be able to control microprocessors and actuators/transducers... That is why I want to buy an USB oscillscope because being it a hobby, I don't wan't to spend a fortune on it. I don't mind spending an extra 20€ or something beyond the hantek value (about 50€), what I would like to know is if these extra 20€ are worth it in the case of OWON.About the speed, actually I don't really know. For example, I would like to be able to debug a good resolution encoder spinning at a couple hundreds rpm for example , or maybe more? I don't know if the 25MHz would do, maybe.... I also would like ot be able to read some signals from car/bikes parts for example...Again, I have no background (degree) in electronics, and this is a hobby, so 200€ scopes are out of my mind...Greetings

author: Seekonk
author_rank: Super Contributor
timestamp: January 07, 2016, 06:47:48 pm
content: That shouldn't be an issue. I used to rebuild encoders for machine tools. This one make used an incandescent lamp. When it burnt out the factory line was you had to buy a new encoder. I started fixing these and the factory rep found out. He started bringing me encoders and I fixed them for $60 each, think he made $200 on each one. It was easy money taking only about 5 minutes. Gave him a key to my car and he would just drive by work and drop them in my truck with an envelope of cash. The lamp filament had to be precisely aligned and there were four resistors on pins that had to be trimmed. These gave a sine wave to be matched and then check differential out for phasing. These were a friction type encoder so the wheel had to be spun with a finger. Had to have a quick eye to catch it on a scope. Sure wish I had capture back then. Never had one come back.

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 07:08:16 pm
content: @mecanico, DSOs in the 20-25MHz class should easily be able to handle the sort of mechanical encoders that you're talking about. For a 25MHz bandwidth (actually more like 30+MHz at -3db) you should be able to observe clean square-waves and timings of at least 10MHz which should be more than fast enough (I doubt if the signals that you are talking about exceed a few hundred kHz at most).Thanks for providing more clarification about your background, budget and needs, it all helps to give you better advice.

author: mecanico
author_rank: Contributor
timestamp: January 07, 2016, 07:15:52 pm
content: Thank you Gyro, I'm leaning towards this OWON, now I don't know about the isolated version or not...

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 07:33:44 pm
content: USB isolation is always useful, but by no means essential. You need to ask yourself whether you could safely connect a port of your computer to what you're working on - for instance a USB interface or serial port, would it create a nasty ground current loop? In most cases the answer is that it's fine. If you are powering your encoders from a bench PSU then you're fine. If you are working on industrial machinery and you are running with a laptop on battery, then again you're fine. Most scopes (including the Rigol for instance) have their input ground connected to mains ground and are fine for most purposes.USB galvanic isolation is useful if you are in a situation where a large ground current would flow if directly connected or sometimes for working in electrically noisy (ground noise) environments.If it helps, be basic VDS1022 PCB has footprints for the isolation components and at least one person has successfully retro-fitted these, so it is possible to do this at a later date (maybe you need to learn a bit more before attempting it).Hopefully this won't be an issue for you anyway. If you're using a laptop then worst case you have the option to unplug it and use on battery for the duration of a troublesome test.Hope this helps.

author: KL27x
author_rank: Super Contributor
timestamp: January 07, 2016, 07:37:21 pm
content: QuoteOut of a mechanical encoder "clean square wave" is not something to be assumed. The scope may be needed to look at the noise/bounce, not the nice clean signal. Reading the output of a mechanical encoder is not necessarily a mundane task. But yeah, a 25MHz scope will still be more than fast enough.

author: TinkerFan
author_rank: Regular Contributor
timestamp: January 07, 2016, 07:37:41 pm
content: Especially if you are planning to observe digital signals, you should consider, that the Owon does not have a built in logic analyzer. But the Hantek has a sample rate we better do not start looking at...PS: Dave has made a video about scope grounds. You might want to watch it before choosing:http://www.eevblog.com/2012/05/18/eevblog-279-how-not-to-blow-up-your-oscilloscope/

author: mecanico
author_rank: Contributor
timestamp: January 07, 2016, 07:40:33 pm
content: Quote from: Gyro on January 07, 2016, 07:33:44 pmWell, I need to get a better knowledge on eletronics, but what I understtod was that if my laptop doens't close the circuit throught its power supply ground I'll be fine correct? In case of that current that you talk about it would burn the laptop, the scope or both?Greetings

author: mecanico
author_rank: Contributor
timestamp: January 07, 2016, 07:42:18 pm
content: Quote from: TinkerFan on January 07, 2016, 07:37:41 pmWell, now I am confused. The hantek HAS and the owon HASN'T a logic analyzeR? Shouldn't it be suposed to be able to observe digital signals with a scope( a constant line with a certain voltage value???)Greetings

author: rrinker
author_rank: Super Contributor
timestamp: January 07, 2016, 08:03:44 pm
content: Quote from: Seekonk on January 07, 2016, 06:47:48 pmOh I remember those things. My first job out of college (and the only one where I actually did EE stuff, before getting switched to computers and networking and software development) was at a CNC and EDM machine shop fixing the machines (and in the case of EDM, building some of my own). Fun stuff, though I don't recall ever trying to repair encoders. We had things of all ages, from brand new to an old GE 550, in which the 'computer' part was an 8080 CPU that recorded the contents of the paper tape and then played it back into the controller with 7 LEDs that simulated the paper tape.

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 08:08:53 pm
content: QuoteYes, absolutely correct.

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 08:18:12 pm
content: QuoteI'm not sure that the Hantek does either, I think the comment was about the Hantek's sample rate issues.To do proper logic analysis a cheap logic analyser is helpful (one of the cheap <$10 ones mentioned previously), this is capable of streaming large amounts of data to your PC (as in your long duration streaming question) and doing protocol decoding (I2C, SPI, serial etc - not that these will be very relevant to your mechanical encoders). One major difference between scopes and LAs is that a scope can see analog signal levels and voltages, the LA can only see digital 1/0s over a narrow (max 5V voltage range) this is probably very relevant for your mechanical encoders. I would suggest picking up one of the very cheap LAs TOO so that you have all bases covered.

author: TinkerFan
author_rank: Regular Contributor
timestamp: January 07, 2016, 08:24:26 pm
content: Quote from: mecanico on January 07, 2016, 07:42:18 pmYou are right, the Hantek has a logic analyzer, whereas the Owon hasn't.A logic analyzer is something similar to a scope, but it only can observe digital signal levels (on/off), but it has a lot of features for that, which a scope doesn't. It has for example 8 or 16 digital channels, instead of just 2. The other thing ist, that it often can decode bus signals, like I²C and SPI. That would be something you could not do easily with a scope. I think that would be quite good for you. But the downside of that scope is, that it is not isolated and that the sampling rate (basically the frequency at which the internal DAC reads the voltages in) is just about twice the frequency, which is really bad. The sampling rate should usually be 4 (better more) the bandwidth of the scope. It would only make sense to use that scope up to 12MHz (or less if you want more than 4samples/s).You can probably exceed the bandwith limit (neglecting the sample rate), because at e.g. 20MHz the signal has just lost about 30%(-3dB) of its amplitude. But I am not an expert on this topic.PS: I just read, that the LA is limited to 10MHz on the Hantek 6022BL and I also read Gyro's comment. So here is the seccond explanation...

author: Gyro
author_rank: Super Contributor
timestamp: January 07, 2016, 08:30:05 pm
content: Ah ha, I see where a confusion has crept in... Hantek 6022be= scope, 6022bl= scope+LA

author: TinkerFan
author_rank: Regular Contributor
timestamp: January 07, 2016, 08:39:57 pm
content: Oh, yes I see...So in that case (the 6022BE]) I would definitely buy the Owon. But if you consider buying a logic analyzer as well, I would start thinking, what I'd use more often.

author: mecanico
author_rank: Contributor
timestamp: January 07, 2016, 10:17:07 pm
content: OH ok, now it makes sense!!! You guys rock!I think that without LA I'll go with owon.Greetings

author: Galenbo
author_rank: Super Contributor
timestamp: January 08, 2016, 07:49:38 am
content: Quote from: mecanico on January 07, 2016, 06:29:34 pmGet a 2-channel battery portable device, do not care about MHZ.

author: Gyro
author_rank: Super Contributor
timestamp: January 08, 2016, 10:00:44 am
content: Quote from: mecanico on January 07, 2016, 10:17:07 pmOne thing you can do in return for the advice you have received from everyone... Please report back on your experiences. Too many people disappear after coming here with questions so we don't get feedback on how well it worked out. It also helps others in a similar situation.

author: V_King
author_rank: Regular Contributor
timestamp: January 08, 2016, 04:16:08 pm
content: was in your situation last spring. rigol 1054z just showed up and was out of my price range. and after getting bored reading all the "expert" opinions on forums, had an option to try Siglent 1102CML, (100MHz, long memory, big screen) and it ticked all the boxes, looked well made and finally found Jack Ganssles' review on it with very positive feedback. bought it for a very reasonable price from uk retailer with warranty etc. and very happy so far. barely use second channel, mostly just debugging digital circuits. for logic work got the logic analyser from dangerous prototypes.don't get bogged down with spending ages on deciding what to use. there will always be somebody unhappy with something. Your kids will not be inheriting it and 5-10 year down the road you either will be using a top end toy in your work place or have plenty of options for really low prices if everything keeps developing at such a paste.

author: rrinker
author_rank: Super Contributor
timestamp: January 08, 2016, 04:23:15 pm
content: I too recently picked up a Siglent 1102CML, for well under MSRP, yet new in the box. Even shipped from a US location so I didn't have to wait long. I was also swayed watching Jack's review of it and felt it would work well for what I need - probably a bit overkill actually. Now I'm itching to get building a new workbench so I can get all set up and start messing around with stuff again, except until I get my bum knee under control I'm not good for much of anything but hobbling back and forth to work. Hauling heavy wood and walking through the store to pick out the required materials is right out for now.

author: mecanico
author_rank: Contributor
timestamp: January 08, 2016, 07:28:34 pm
content: That Siglent would be awesome, however to expensive...Thanks for the info!When I receive it I will post and update this!Greetings