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Offline tvlTopic starter

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Is An Oscilloscope Practical
« on: January 02, 2019, 07:26:30 pm »
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« Last Edit: March 10, 2019, 12:19:32 am by tvl »
 

Offline tooki

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Re: Is An Oscilloscope Practical
« Reply #1 on: January 02, 2019, 07:30:21 pm »
I’m not sure what your end goal is, but I (as someone who does electronics purely as a hobby), I found that getting a scope massively improved my understanding of real world circuits. Without a scope, we’re essentially blind to signals.

So if you are going to do electronics, my vote would be an unqualified “yes!”

But if you’re going to do more electrical work, the value drops tremendously. (Never mind that scoping mains safely is non-trivial when not using a specially isolated scope like the Fluke ScopeMeters.)
 

Offline tggzzz

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Re: Is An Oscilloscope Practical
« Reply #2 on: January 02, 2019, 08:00:34 pm »
For anything "mains related" make very sure you have the right probes, lest you damage your equipment and/or yourself.

Never disconnect a scope's protective mains earth.

FFI about probing, especially w.r.t. safety, see https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/
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Offline soldar

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Re: Is An Oscilloscope Practical
« Reply #3 on: January 02, 2019, 08:01:45 pm »
I've been toying with the idea that maybe I should purchase a scope for myself. I have interest in viewing the waveform from my new AC standby generator and possibly checking some power supplies, but other than that, I'm not sure if a scope would do me much good. I'm wanting to learn some new things with my free time, but I'm not so sure how far I would get with a scope.

I've been looking at the Siglent SDS1202X-E ($359.00) ....... I'm sure this is way more scope than I need, but I'd appreciate some guidance. Is there anything else available that will serve me just as well, cost less and still provide accuracy OR is it best I get something like the model I'm looking at just in case I do "like what I see".  Or better yet, is a scope a waste of money for someone like me???
A scope will give you a view of what is happening in a circuit which no other instrument can give you. If you just want to see the output of your genset then it is probably not worth buying one unless you have plenty to spend. If you are going to be building and troubleshooting electronic circuits then yes. If you are not entirely sure you can always buy a cheap/used unit and move up later if warranted or resell it if it turns out you are not using it.

I have a *really* old Hameg and it works fine for my limited needs. I do not need it often but when I need it I really do need it.

I remember when I was beginning and I had an audio amplifier which I had built and I just could not get it to work. After too many wasted hours trying to troubleshoot the darn thing I got a scope and hooked it up and immediately the cause became apparent: the dang thing was oscillating at some hundred KHz. Of course, there was no way to see this on my multimeter.
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Offline GregDunn

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Re: Is An Oscilloscope Practical
« Reply #4 on: January 02, 2019, 08:05:04 pm »
Yes, if you're looking at signals, a scope is vital.  Even when looking at DC, many meters provide a filtered value which obscures noise and ripple behavior.  I just built a linear power supply and seeing the actual trace of the voltage input to the regulator made it an easy job to optimize the capacitance so that the result stayed above the dropout value regardless of the load.  It also shows any spikes on the waveform which might indicate issues.

And, of course, measuring mains voltage is always a concern unless you can isolate it adequately from neutral; but even then, some kind of scope is extremely helpful to see what your AC looks like.  Distortion or asymmetry might indicate power distribution issues or even home wiring problems.  You won't be able to analyze those with a meter.
 

Offline james_s

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Re: Is An Oscilloscope Practical
« Reply #5 on: January 02, 2019, 08:09:42 pm »
This seems like one of those cases where an older, basic analog scope would be ideal. Something like a 20-50MHz instrument which you should be able to pick up for <$50 with a little luck depending on your location. Unless you've got money to burn or are planning to seriously pursue electronics as a hobby there is little benefit to spending hundreds on a fancy new scope.
 

Offline james_s

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Re: Is An Oscilloscope Practical
« Reply #6 on: January 02, 2019, 08:24:45 pm »
Well don't rush out and pay top dollar for an old scope, but you might find one for little or nothing. I've given away two scopes over the past few years, there are a lot of older analog scopes collecting dust in closets and garages, it's worth a look around.

There are lots of ways of learning electronics, books, youtube videos, websites, it helps to have an idea of what you want to do.
 

Offline rstofer

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Re: Is An Oscilloscope Practical
« Reply #7 on: January 02, 2019, 08:35:22 pm »

I'm not even sure of my end goal. Would a scope help ME better understand real world circuits WITHOUT any formal training in electronics? Or would that be difficult at best?


In the electrical realm, they're pretty useless.  Even if you know a utility waveform is trash, what are you going to be able to do about it?  I don't probe mains, there's nothing there I can improve.

For electronics, if your goal is to learn electronics as a hobby, yes, a scope is almost required.  Watch W2AEW's transistor video to see examples of how he uses a scope.



If you want to do educational circuits, I have a couple of points to make:  First, you not only need to see the output, you need to be able to generate the input.  In the video above, the author doesn't make a point of showing his signal generator.  Second, there is a cheaper and better way to get started.  Consider the Analog Discovery 2.  It has a 2 channel signal generator, a 2 channel scope, a 2 output power supply, 16 bits of digital IO and a host of 'tools' in software.  For students and those just coming in to the hobby, this is an ideal tool.

Watch the lab videos to get an idea of how the AD 2 is used in practice.  The first 2 or 3 lab videos should get you started.  Take the whole class if you want but the math does get going by chapter 3.

https://learn.digilentinc.com/classroom/realanalog/

To follow along with the course, you probably need the "Pro Bundle"
https://learn.digilentinc.com/classroom/realanalog/
and the analog parts kit
https://store.digilentinc.com/analog-parts-kit-by-analog-devices-companion-parts-kit-for-the-analog-discovery/

You can download the Waveforms software and play in Demo mode just to get a feel for the tools provided.

Just look at the Features:
https://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/
« Last Edit: January 02, 2019, 08:36:56 pm by rstofer »
 

Online Kleinstein

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Re: Is An Oscilloscope Practical
« Reply #8 on: January 02, 2019, 08:44:00 pm »
There are different ways of learning electronics. One is more hands on the real instruments and a soldering iron.
At least for the beginning a lot can be done without a scope, e.g. with just a DMM. So there may not be a hurry to get the scope and one could wait for a good offer.

One can also learn quite a bit from the theoretical side - e.g. reading and using simulators.

There are also cheap scope like tools, like using the soundboard or a µC board. This maybe sufficient for the very basic experiments, though these are quite limited (e.g. low BW so one may not see an OP oscillating).
 

Offline rstofer

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Re: Is An Oscilloscope Practical
« Reply #9 on: January 02, 2019, 08:51:11 pm »
Understanding circuits requires Ohm's Law E=I*R or Voltage = Current times Resistance.  This is the first important concept and it is profound.  Here's an example of how it would show up in a hobby environment:

Say you have a red LED and you find out somewhere, like the datasheet, that it will drop 1.65V (Vf spec) with a current of 20 mA (If spec).  You have a 5V supply and you know you want to drive the LED in accordance with the numbers above.  How to size the dropping resistor?

Well, the resistor has to drop what the LED doesn't (series circuit, same current through every component) so (5 - 1.65) or 3.35V at 20 mA.  R = E / I = 3.35 / 0.020 = 167.5 Ohms.  Well, the closest I have is the common 220 Ohms, good enough!  I chose a bigger resistor to guarantee lower current.  The LED won't be maximally bright but it will be bright enough.

https://www.alliedelec.com/m/d/6355b8aba0b01578df0bb7b871ceefd7.pdf

The point is, you can't even light an LED without Ohm's Law.  Or, you could just remember 220 Ohms for a red LED on 5 volts.

Actually, you might try 470 Ohms and find it bright enough.  Maybe even 1000 Ohms.  But at least you know the lower bound - 167.5 Ohms

Right after that we get to circuit analysis and things get more complex.  I really like the Real Analog program at Digilent (linked above)   You might try the Electrical Engineering program at Khan Academy.
 

Offline soldar

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Re: Is An Oscilloscope Practical
« Reply #10 on: January 02, 2019, 09:53:50 pm »
I'm not even sure of my end goal. Would a scope help ME better understand real world circuits WITHOUT any formal training in electronics? Or would that be difficult at best?
No, a scope is not going to help you understand. I would recommend a lot of reading online, videos, etc. that explain how things work. Then, when you want to build and troubleshoot that is when you need the tool.

If you do not know if you need something then you don't need it. When you get to the point where you think you need a scope for a particular purpose then you need it. You will know you could use a scope for a purpose when you have the knowledge. The scope does not bring the knowledge. You have to supply that. You need to gain the understanding first. Then you need the tools to use that knowledge that you have. Again, you can spend hours learning from online resources without spending a dime and without leaving the comfort of your chair.
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Offline tooki

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Re: Is An Oscilloscope Practical
« Reply #11 on: January 03, 2019, 02:40:37 am »
I do not have formal training in electronics, and I found a scope to be enormously helpful in learning. When you’re reading up about electronics, it’s all theoretical when it’s on paper. Building a circuit brings it to life, and for that, you need test gear to measure and see the results.
 
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Offline Mr. Scram

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Re: Is An Oscilloscope Practical
« Reply #12 on: January 03, 2019, 03:30:01 am »
No, a scope is not going to help you understand. I would recommend a lot of reading online, videos, etc. that explain how things work. Then, when you want to build and troubleshoot that is when you need the tool.

If you do not know if you need something then you don't need it. When you get to the point where you think you need a scope for a particular purpose then you need it. You will know you could use a scope for a purpose when you have the knowledge. The scope does not bring the knowledge. You have to supply that. You need to gain the understanding first. Then you need the tools to use that knowledge that you have. Again, you can spend hours learning from online resources without spending a dime and without leaving the comfort of your chair.
I disagree, honestly. Both an oscilloscope and a multimeter are tremendous tools to help you understand what's going on. Without knowing what's going on in your circuit, it's very hard to get a good grasp on what is happening when and why. As you can't see electrons, both tools serve as your eyes as a substitute.
 
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Offline IanMacdonald

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Re: Is An Oscilloscope Practical
« Reply #13 on: January 03, 2019, 10:13:51 am »
A trainee once asked my why I was using a 'scope to check a DC supply rail. I explained that it was supposed to be DC, but that didn't guarantee that it was DC.

A multimeter may give the same reading whether it's DC, pulses or poorly rectified AC. For example the inexperienced guy checks a computer PSU with a multimeter, sees +5 and +12, decides it can't be the PSU and starts swapping a whole load of parts that aren't faulty.  |O

The experienced guy checks it with a scope and gets the fault rightaway, that there's a substantial AC ripple on one of the lines.  :-+ Not only that but the nature of the ripple suggests a dried-up electrolytic on that rail. He peeks in through a ventilation slot and sees the bulging object behind it. Fault diagnosed.

 
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Offline Jwillis

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Re: Is An Oscilloscope Practical
« Reply #14 on: January 03, 2019, 10:45:28 am »
I'm not as experience as most people here with even less experience with an oscilloscope.Wish to some day get a proper DSO. But I already find my analog an indispensable tool to find whats going on in a circuit. I would be completely blind without it and learn absolutely nothing. 
 

Offline IanMacdonald

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Re: Is An Oscilloscope Practical
« Reply #15 on: January 03, 2019, 11:55:33 am »
"proper DSO"

DSOs do have advantages, for example storage on an analog scope will cost a fortune and involve a massive unit. However, it's the difference between seeing for yourself and having a computer tell you what it thinks it sees. The latter might sometimes be more accurate, but can also be wildly off and you won't necessarily know. For example with aliasing.  Obviously price and quality play a part here!
 

Offline soldar

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Re: Is An Oscilloscope Practical
« Reply #16 on: January 03, 2019, 12:17:53 pm »
Well don't rush out and pay top dollar for an old scope, but you might find one for little or nothing. I've given away two scopes over the past few years, there are a lot of older analog scopes collecting dust in closets and garages, it's worth a look around.
I agree. When you don't really know if you are going to take seriously into a certain hobby then the best course is to buy something used / low cost which can let you begin and give you a feel. If you want to get involved more deeply you can then get better equipment.  There are USB oscilloscopes on ebay for very little or you can get a used older model.

The main thing is that a scope is just a tool that will allow you to gain information but it is of no use if you do not know what information you need.  If you have an audio amp or a power supply which you are troubleshooting you first need to understand the circuit and how it works and what signals you should expect at each point. The scope is not going to tell you that information. Once you know all that you use a scope to confirm the signals are what they should be or not. The scope does not tell you what they should be. You have to know that on your own.  Like a wrench does not tell you how to fix your car, it just allows you to do it if you know how.
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Offline Jwillis

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Re: Is An Oscilloscope Practical
« Reply #17 on: January 03, 2019, 12:20:05 pm »
All I have in a DSO is a Hantek 6022BE .It's not bad for some things but the software really sucks and crashes a lot.
 

Offline GeoffreyF

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Re: Is An Oscilloscope Practical
« Reply #18 on: January 03, 2019, 01:16:54 pm »
I think the Rigol 1054 is a good entry level scope. The two channel version is also fine but you may wish to measure more than 2 points in your circuits.

As a rule of thumb, a scope of a particular bandwidth is most useful for 1/5 of that bandwidth. A 50 mhz scope is of limited use above 10 mhz, which is fine if you are looking at Audio or microprocessor type stuff. The reason for this is that the main value of looking at a trace is the harmonics or capacitive/inductive effects on fast rise times.  For that you need the extra mhz.

Above about 200mhz, the skill set to get an accurate reading increases.

As already mentioned, be very careful with the ground lead.  If the unit under test is mains connected or grounded, I measure current between the scope ground and the ground of what I am testing before I proceed.
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Offline soldar

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Re: Is An Oscilloscope Practical
« Reply #19 on: January 03, 2019, 01:32:11 pm »
As already mentioned, be very careful with the ground lead.  If the unit under test is mains connected or grounded, I measure current between the scope ground and the ground of what I am testing before I proceed.
Yup. Before digging into a device study it carefully, especially the power supply part. If anything is not totally isolated from the mains I use an isolation transformer. 
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Offline BillyD

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Re: Is An Oscilloscope Practical
« Reply #20 on: January 03, 2019, 02:29:10 pm »
Given that you have already have some knowledge of repairing PCs I think it's likely that you'll go at least some way beyond looking at AC waveforms for at least some of the time.
Personally I'd consider those old analogue scopes very niche at this stage; while they're good for dealing with a nice clean regular repeating signal they quickly get frustrating with anything more complex.
Whereas even a basic DSO will let you capture and review both once-off digital and analog signals and waveforms with ease.
And, importantly, they take up a fraction of the space on the bench.
A DSO opens up a whole new world of 'seeing' electricity as others have mentioned above, it's probably one of the most exciting electronic tools you can get.

 

Offline jazper

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Re: Is An Oscilloscope Practical
« Reply #21 on: January 04, 2019, 02:14:23 am »
In that budget range you may be able to squeeze a rygol 4 channel scope which you can "tweak" to 100mhz - the venerable 1054z

4 channels are better than two, and even in its default guise of 50mhz you will get a lot of value out of it

If the hobby falls through, you can always sell the scope
 

Offline alsetalokin4017

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Re: Is An Oscilloscope Practical
« Reply #22 on: January 04, 2019, 02:22:55 am »
Of course you need an oscilloscope. If you didn't, you wouldn't be asking about one on this forum! More importantly, you _want_ an oscilloscope. You know you do! And you also know that cheap tools are no bargain. So get the most scope you can afford, bearing in mind that, at present, it's like a baby: you don't know what use it might be in the future.
Something like the Rigol DS1054z or the Siglent or GWInstek similar models will make you proud. If you are really on a budget and enjoy self-improvement hobbies you might consider a good used analog scope, but something tells me you can afford one of the entry-level DSOs.
The easiest person to fool is yourself. -- Richard Feynman
 
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Online tautech

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Re: Is An Oscilloscope Practical
« Reply #23 on: January 04, 2019, 02:32:06 am »
Years ago a great friend and Dr of EE said to me if he had to choose just piece of TE it would be a good oscilloscope....it can be a Voltmeter, Frequency counter, Spectrum analyser and of course a scope.

The compedant technician uses it for all these uses and I’ve sold many a SDS1202X-E into the repair industry.
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Offline joeqsmith

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Re: Is An Oscilloscope Practical
« Reply #24 on: January 04, 2019, 03:02:58 am »
I've given three analog and a digital one away over the past few years.   Maybe post your state.  Who knows, maybe someone has one that lives near by.   I had a guy want to give me an old Tec scope not too long ago.    Maybe check Craigslist. 

Good luck with your new hobby and retirement.


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