What can't I do with a $60 scope?

[Shoitah]

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.

[ataradov]

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.

[Whales]

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?

[Shoitah]

@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.

[rstofer]

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.

[ataradov]

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.

[Ed.Kloonk]

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?

My 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 to safely feed 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.

[andy3055]

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.

[mwb1100]

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.

[Shoitah]

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.

[Ed.Kloonk]

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.

I think the consensus is that a $60 scope is more likely to disappoint you than not.

[ataradov]

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.

[Shoitah]

@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.

[ataradov]

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.

[BravoV]

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.

[barshatriplee]

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.

[Shoitah]

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.

Sort 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.

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.

I'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.

[wraper]

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.

[Haenk]

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.

[rstofer]

I'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.

Most 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/B07F65SZMV

These 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...

[Giedrius115]

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.

[Shoitah]

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 splurging  on 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!

[jonpaul]

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 issues


Jon

[ataradov]

In Paris I find old analog scopes made in Fraqnce or Germany for perhaps 5..50 EU.

This 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.

[jonpaul]

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 work

ENJOY!


Jon