What can't I do with a $60 scope? - Page 1
Forum section: electronics / beginners

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 12:59:11 am
content: Hi. First time user here. I was considering getting a cheap oscilloscope to investigate some issues I've been having with the mains power in my house (flickering lights, etc...) and I wanted to be able to view the 120v waveform. Searching on amazon, I was able to find some <200kHz oscilloscopes for ~$35. However, after looking at some reviews online, most people suggested that cheap (<$300) oscilloscopes just aren't very capable. Now, I do dabble in electronics, and it's not inconceivable that I might want to more seriously use an oscilloscope in the future. I'm quite confident that even the cheapest scope will be able to handle a 60Hz sine wave, but I'd like to justify the purchase of such an oscilloscope by knowing that I can also use it for electronics work in the future. So my question is, what are the limitations of a sub $60 (I'm not willing to spend more) oscilloscope? Would it be useful for some electronics work, or would attempting to do so be futile? At what point would I reach the limits of what such a scope could do?Thank you.P.S. I am aware of the safety concerns of dealing with mains electricity, as well of the fact that you can't just plug 120v into any oscilloscope. My question just pertains to how far a <$60 oscilloscope will take me.

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 01:10:14 am
content: What do you expect to see there and how do you plan to deal with it? Oscilloscope is pretty much the least useful tool here. Electrician's screwdriver with a neon light is far more useful.Short answer - $60 scopes are junk and waste of money, pretty much always.If you are willing to rick your life, then they would show you 60 Hz sine wave. But I don't see how this is helpful when dealing with electrical issues.

author: Whales
author_rank: Super Contributor
timestamp: April 05, 2023, 01:12:59 am
content: Do the lights constantly flicker, or only briefly flicker? The latter will be harder to capture, the former might be doable on a cheap scope.What type of lights?The scope might be useful to confirm that it's the power lines and not the lights (and from there contact your power company).EDIT: why was there a facepalm smiley here?

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 01:27:40 am
content: @Whales , it's an occasional issue, but sometimes reproducible when certain loads are running. I'd like to see if voltage spikes/drops are the issue.

author: rstofer
author_rank: Super Contributor
timestamp: April 05, 2023, 01:50:35 am
content: So, you want to trigger on the occurance of some phenomenon and save the display. This is known as 'single shot trigger'. Very few analog scopes had this capability but most DSOs do. Make sure anything you buy has this feature.Determining how to set up the trigger is the issue. Some of the better DSOs can put a high and low limit band around a nominal waveform. I'm not sure how this plays with single shot triggering. Try to get the User Manual off the Internet.As posted above, unless you have some way to clean up the incoming utility power, why bother looking at it? If the problem is generated internally, you can probably correlate the cause and effect without a scope.

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 01:55:08 am
content: There is not a single < $60 scope that would let you set a trigger mask. And otherwise triggering on intermittent AC issues is not easy. Long memory depth is a better feature here, but again, not going to happen in a cheap scope.Reasonably fast responding multimeter is a far better tool for this. You will see the voltage drop and you can track it down along the way. There is no reason to see a sine wave.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 05, 2023, 02:01:08 am
content: Quote from: Whales on April 05, 2023, 01:12:59 amMy question is, with a $60 budget, what then could you do about the cause of the flicker if you happen to identify it?Maybe part of the $60 would be better spent on an Arduino or similar with old transformer tosafelyfeed the AC signal into the Arduino. You could then customize the software to capture and retain whatever it is that you are looking for.Just a thought.

author: andy3055
author_rank: Super Contributor
timestamp: April 05, 2023, 02:02:33 am
content: You are going on a very dangerous path not knowing how or when and where you can use an oscilloscope. Please go on YouTube and search for how not to blowup you oscilloscope. Dave's clip comes up at the top. Watch it first and you will change your mind on this idea... I think. It is for your own safety.

author: mwb1100
author_rank: Frequent Contributor
timestamp: April 05, 2023, 02:11:55 am
content: Let me start by saying that all I know about troubleshooting household AC is testing whether or not an outlet has 120V. That said, would something like a Uni-T UT161D be useful here? It has decent input protection (I believe) and includes logging to a PC. You can get a UT161D for less than $70 on Aliexpress.

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 03:18:52 am
content: I seem to be getting mixed responses here. Some of you seem to be saying that a $60 oscilloscope won't work for my application, while some others are saying that it's overkill. To clarify, I am not necessarily interested in solving the issue right now; just in finding the root cause (it's probably my utility). For the sake of knowledge I would like to know what is going on with my electricity. The flickering usually goes on for a while, so I'll be able to just hook up the scope while it's happening; I shouldn't need to set a trigger. If a $60 oscilloscope won't even be able to show me ongoing problems with my AC waveform then I certainly won't get it; but if it can, I would like to know how it would fare for regular electronics work.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 05, 2023, 03:34:50 am
content: Quote from: Shoitah on April 05, 2023, 03:18:52 amI think the consensus is that a $60 scope is more likely to disappoint you than not.

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 03:35:41 am
content: It is overkill to use any scope in this situation regardless of the price.Keep in mind that oscilloscopes are not really measurement tools, they are primarily for showing waveform shape. It would still show dips big enough to to dim the lights, but don't expect accurate measurements.Multimeter is far better suited for this.And if you are worried that is not not a sine - don't worry, it is unless your wiring and loads are VERY screwed up.

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 03:38:21 am
content: @atadarov , I suspected that an oscilloscope would be overkill. But it's more of a justifiable purchase if I could use it for other purposes as well. That's why I want to know what it's limitations are for electronics work.

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 03:40:34 am
content: They are still a disappointment for that. Cheap scopes UI sucks. So much that you won't want to use it.Reasonably useful scopes start at $250, it is far better to not waste the money and put them towards a real scope if you plan on doing electronics.

author: BravoV
author_rank: Super Contributor
timestamp: April 05, 2023, 04:23:35 am
content: As you keep emphasizing on seeing the waveform wiggles, even it may not solve your problem, so is it just for the curiosity sake to watch the wiggly waveform ? As its fun to watch though, for 1st few seconds.

author: barshatriplee
author_rank: Regular Contributor
timestamp: April 05, 2023, 05:37:52 am
content: What is the maximum input voltage of the oscilloscope that you are considering to buy? I came across some pocket oscilloscopes like the DSO Nano series. Those oscilloscopes only had a maximum input voltage of 80V peak to peak. That's obviously less than the line voltage.

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 01:25:56 pm
content: Quote from: BravoV on April 05, 2023, 04:23:35 amSort of, but it's also useful if I want to call my utility with pertinent details, and it will also help me easily quantitively verify when the problem gets fixed. Of course, there'd be a better justification if it's useful for other things as well.Quote from: barshatriplee on April 05, 2023, 05:37:52 amI've found some that can handle mains power, though many can't. For one of those I'd have to find some way of reducing the voltage.

author: wraper
author_rank: Unknown
timestamp: April 05, 2023, 01:32:32 pm
content: Flickering does not happen due to distorted waveform but because of voltage changes. If mains voltage stays within spec, the only sensible way how to deal with flickering lights is to replace them with something not sensitive to voltage fluctuations. Like non dimmable LED with a switch mode driver.

author: Haenk
author_rank: Super Contributor
timestamp: April 05, 2023, 01:36:43 pm
content: There are long term recording devices made exactly for this use case. Unfortunately not available for a 2 or 3 digit amount.The line noise usually comes from motor starts - check HVAC units or refrigirators.

author: rstofer
author_rank: Super Contributor
timestamp: April 05, 2023, 02:13:16 pm
content: Quote from: Shoitah on April 05, 2023, 01:25:56 pmMost scopes come with a set of switchable probes - 1x and 10x. In the 10x switch position, the voltage is divided by 10. So, a 120V RMS signal will look like 34V peak to peak. There are 100x probes around, Amazon has them:https://www.amazon.com/Oscilloscope-Accessory-Voltage-100MHz-Bandwidth/dp/B07F65SZMVThese will divide the voltage by 100 and result in a 3.4V peak to peak signal.Or, run the 120V through a step down transformer 120V - 6V sounds good.There is very little use for the 1x setting, even on professional scopes. Glue the switch in the 10x position. Then, if you really need 1x, buy a set of probes with only 1x capability, no 10x switch. There can be a real problem if you think the switch is in 10x and it is really in 1x. I bought a nice pair of 10x fixed probes from ProbeMaster. No switch to misadjust...

author: Giedrius115
author_rank: Newbie
timestamp: April 05, 2023, 03:47:20 pm
content: A 60 buck scope is more sort of something to get for a kid on his 12th birthay if hes interested in electronics. Sure you will see some stuff on it, but will it be accurate? Who knows. Can you trust it? Absolutely not. With that being said, if you care even a bit about your own safety I would strongly advise to not get anywhere even close to mains with that thing. Also, if the specs say it can handle 80V peak to peak, I would trust half of it, so maybe 40V peak to peak.

author: Shoitah
author_rank: Newbie
timestamp: April 05, 2023, 04:47:49 pm
content: Thanks for all the responses! It definitely sounds like to me that if all I want to do is view my mains power, there's no point in splurgingon a $60 oscilloscope as it still won't be useful for anything serious. Maybe I'll get a ~$30 one from amazon just for this purpose, and @rfoster, a 10X probe sounds like a good idea!

author: jonpaul
author_rank: Super Contributor
timestamp: April 05, 2023, 04:52:39 pm
content: in 1950s..1960s we did everything with a basic 1 or 2 ch analog perhaps 5..10M BW.By 1970s 100M TEK 465, 475 were the workhorse.In Paris I find old analog scopes made in Fraqnce or Germany for perhaps 5..50 EU.Fine for most work.But probing a mains line for transients is NOT easy or likely to find the issues with ANY scope.A power transient analyzer is needed as the events may occur ONCE in a week.Call your utility company if the power has such issuesJon

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 04:56:23 pm
content: Quote from: jonpaul on April 05, 2023, 04:52:39 pmThis is cool, but there is no need to post this in every topic that mentions scopes.Yes, in the old days we had to deal with analog scopes. Thankfully old days are over and we actually have good equipment now.

author: jonpaul
author_rank: Super Contributor
timestamp: April 05, 2023, 06:03:43 pm
content: my point is that an engineer or tech can make best use of almost any scope and that a simple analog scope is fine for 90% of workENJOY!Jon

author: ataradov
author_rank: Super Contributor
timestamp: April 05, 2023, 06:20:58 pm
content: Was this thread started by an engineer or a tech?Suggesting to a beginner to use old 5.50 EU analog junk is just a bad advice. Suggesting anyone to use an analog scope in 2023 is a bad advice. If you already have one and have nothing else, sure. But getting a new one is just a waste of time and money.

author: james_s
author_rank: Super Contributor
timestamp: April 05, 2023, 06:44:10 pm
content: A scope is definitely not the right tool for this job, and those really cheap scopes are little more than toys. They're fine for playing around with arduinos and such but they aren't serious tools. A multimeter with a decent analog bargraph and min/max mode is a much better tool for the job you have in mind. Looking at the waveform on a scope isn't likely to tell you much, as somebody else said it's very difficult to trigger on glitches in an AC waveform.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 05, 2023, 07:01:14 pm
content: Quote from: wraper on April 05, 2023, 01:32:32 pmYou're right if the fickering can be seen with our eyes it happens relatively slow and thus a meter should show it.

author: Bud
author_rank: Super Contributor
timestamp: April 05, 2023, 07:24:49 pm
content: You can do the entire stack of audiophoolery with it and be paid for life.

author: james_s
author_rank: Super Contributor
timestamp: April 05, 2023, 09:48:10 pm
content: That all said, scopes *are* fun to play with, so if you just want a toy and 60 bucks isn't going to compete with putting food on the table then go ahead and pick one up, there's lots of learning you can do with a very cheap scope, just don't expect it to solve many actual problems.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 05, 2023, 10:45:12 pm
content: You need to be careful to measure AC line voltage with a scope.

author: BillyO
author_rank: Super Contributor
timestamp: April 06, 2023, 12:26:07 am
content: Just like to mention several things.First, for $60 you can get something like a DSO154Pro (the one with the built in battery and the 18MHz bandwidth). It's no $15,000 Tek or Agilent, or even a $600 Siglent, but it can be a useful tool for many things. Audio, Arduino projects, old 8-bit computers from the 70's and 80's, DIY digital farting about with 74LS series logic, etc.. However, do not ever hook such a thing up to mains. Ever.Second, generally a scope is not the right tool to muck about with mains for a load of reasons, least of which is the HV probe you should be using for such things would easily cost $200 by itself. That's assuming the scope is already isolated.So, no, this is not going to end well with a "$60" scope.Finally, ataradov could relax a little.

author: james_s
author_rank: Super Contributor
timestamp: April 06, 2023, 01:07:17 am
content: I have a nice Tek DSO and a proper HV differential probe, I can and have looked at the mains waveform, there isn't really all that much to see, it's pretty much the same thing you see on the scope by just touching the probe with your finger to act as an antenna.I actually tried to use it to diagnose an issue once, when powering my house from my inverter generator the bedroom light which is on a dimmer flickers slightly when dimmed. I connected the scope to the wall and found a nice clean looking sine wave that looked significantly nicer than what I get from the utility. I tried everything that I could think of and couldn't see any sort of glitch or anomaly, something must be there but it's not anything I could figure out how to trigger on. Point is unless something is drastically wrong you probably won't see the problem on a scope.