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Offline sx57Topic starter

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need an oscilloscope on a very low budget
« on: December 04, 2022, 09:50:58 pm »
hello dear friends
I want to make a web site about cables and chargers for cell phones like apple,Samsung and etc.
As you know modern phones use switched-mode power supply chargers capable of power delivery or quick charge and other fast charge standards.
I wanted to review such chargers, specially their output quality ,parameters like ripple and noise that need an oscilloscope.
I live in Iran and everything is very pricey under heavy sanctions and I have about 60 dollars budget .so I can buy hantek PSO 2020.
Do you think this oscilloscope can measure ripple and high frequency noise well enough considering that switching frequency of modern chargers is very high?
Is the sampling rate enough? if I am right the true sampling rate of this model is 48ms not 96ms.maybe even lower.
What about the bandwith do you trust the hantek in that regard?
There is also hantek 6022BE with two channels and no ac coupling . don’t know if that is a better option.
I found some owon models for about 2 to 3 times the price and I could not afford them.
Do you think I must save more money and buy one of them? i mean owon rds 1021 or 1022.
My most important need is to verify if the chargers output good quality dc current for the phones. if you think that I have to measure other parameters other than ripple and noise please notify me.
Thank you all .

 

Online wasedadoc

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Re: need an oscilloscope on a very low budget
« Reply #1 on: December 04, 2022, 10:49:17 pm »
Note that m is an abbreviation for milli which is a thousandth (1/1000) whereas M is an abbreviation for Mega which is a million (1,000,000).
 
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Offline Manul

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Re: need an oscilloscope on a very low budget
« Reply #2 on: December 04, 2022, 11:30:31 pm »
I would also build an electronic load, prefferably variable. Using phone as a load is not very scientific and may lead to various inaccuracies. Decent multimerer is a must for accurate voltage measurements. You may want to measure voltage at maximum load. That indicates cable quality (voltage drop). Crappy cables might drop a lot, which is also a sign that they are likely less mechanically robust and may break easily.

Now the noise measurement is more difficult. I recommend you to study the subject. You should use ground spring, not ground clip. It will depend what point you probe. Probably you want some nominal bypass capacitor directly at probing point. You might want to use common mode filter, because your measurements may get polluted by common mode noise. Is 20Mhz bandwidth enough? Borderline. 20mV per division is certainly not very sensitive. Is it on 10X or 1X? If it is 1X, then at 10X it will be 200mV per division, beware!

I would also test isolation voltage of the chargers. This would be destructive and requires special equipment. But knowing that cheap chargers regulary shocks and kills people, that is really relevant test.
 
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Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #3 on: December 05, 2022, 08:24:30 am »
Thank you.very helpful points .what about oscilloscope models i mentioned or any other suggestions?
 

Offline MrAl

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Re: need an oscilloscope on a very low budget
« Reply #4 on: December 05, 2022, 01:54:25 pm »
Thank you.very helpful points .what about oscilloscope models i mentioned or any other suggestions?

Probably want to stay away from some models.
Look for the thread in the Test Equipment section with title "What brand name oscilloscope" or something like that there is a big discussion about scopes and that some are not very good.

Here it is:
https://www.eevblog.com/forum/testgear/best-brand-name-for-an-oscilloscope/
 
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Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #5 on: December 05, 2022, 01:57:33 pm »
thanks mate i will look into it.
 

Online Gyro

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Re: need an oscilloscope on a very low budget
« Reply #6 on: December 05, 2022, 02:09:36 pm »
Certainly the VDS1022 (preferably the 1022I isolated version) over the 6022BE, it performs much better, and [Edit: as you say,] the 6022BE doesn't have AC coupling capability, so it wouldn't be possible for it to display low level ripple superimposed on the DC supply.

More of an issue with cell phone chargers is safety rather than ripple. DiodeGoneWild shows many teardowns of electrically unsafe adapters (you may have some difficulty with his accent)...  https://www.youtube.com/channel/UCQak2_fXZ_9yXI5vB_Kd54g/videos
« Last Edit: December 05, 2022, 02:14:55 pm by Gyro »
Best Regards, Chris
 
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Offline xmris

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Re: need an oscilloscope on a very low budget
« Reply #7 on: December 05, 2022, 06:47:21 pm »
thanks mate for this link... real epic videos there like SMD soldering using ... soldering gun :-}
READY.
 

Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #8 on: December 05, 2022, 08:23:09 pm »
Thanks alot mate.
 

Offline Paul Moir

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Re: need an oscilloscope on a very low budget
« Reply #9 on: December 06, 2022, 06:48:02 am »
I have no opinion which oscilloscope you should buy, but would like to say that AC coupling is not difficult to make yourself.  This is the input section of a Textronix 465 100MHz oscilloscope.  The AC coupling is provided by C3 in series with the input signal.  You could add this externally since it doesn't matter much where in the input path it is placed.  It doesn't need to be 0.19uF:  0.1uF should be plenty for looking at 50Hz since it would be like a 33Kohm resistor.

The operation of the selector switch isn't easy to understand from the schematic, but in the middle "GND" position it discharges C3 through R3 in case a high voltage DC charge has accumulated in C3.  This is to prevent the voltage from being applied to the input when the switch is further turned to the "DC" position.  R4 prevents the capacitor from accumulating a charge when the switch is in the "DC" position.
 
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Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #10 on: December 06, 2022, 08:56:11 am »
I have no opinion which oscilloscope you should buy, but would like to say that AC coupling is not difficult to make yourself.  This is the input section of a Textronix 465 100MHz oscilloscope.  The AC coupling is provided by C3 in series with the input signal.  You could add this externally since it doesn't matter much where in the input path it is placed.  It doesn't need to be 0.19uF:  0.1uF should be plenty for looking at 50Hz since it would be like a 33Kohm resistor.

The operation of the selector switch isn't easy to understand from the schematic, but in the middle "GND" position it discharges C3 through R3 in case a high voltage DC charge has accumulated in C3.  This is to prevent the voltage from being applied to the input when the switch is further turned to the "DC" position.  R4 prevents the capacitor from accumulating a charge when the switch is in the "DC" position.
thanks a lot friend. this way i can make one if i buy 6022be. i think 6022 is not gonna do what i need so i am thinking on increasing the budget. i am doubtful about pso 2020 too. hope others share their suggestions and experiences.
 

Online Adrian_Arg.

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Re: need an oscilloscope on a very low budget
« Reply #11 on: December 06, 2022, 10:41:34 am »
At some point they lent me a hantek 6022be or BL I don't remember well, it had a built-in logic analyzer, for hoobist use it works well, I have seen that they also use it in automobiles, the bad thing I see, few trigger modes, it has no coupling CA (you can make a homemade one), in windows 7 it works fine, in windows 10 it was labeled, we are talking about a 60 dollar team, but to begin with it works,

in spanish
En algun monento me prestaron uns hantek 6022be or BL no recuerdo bien, tenia analizador logico incorporado, para el uso hoobista funciona bien, lo he visto que tambien lo usan en automotores, lo malo que le veo, pocos modo de trigger, no tiene acoplamiento CA(se puede hacer uno casero), en windows 7 va bien, en el windows 10 se me tildaba, estamos hablando de un equipo de 60 dolares, pero para empezar funciona, 
 
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Offline tatel

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Re: need an oscilloscope on a very low budget
« Reply #12 on: December 06, 2022, 12:40:58 pm »
I'm not an expert at all, but I have many times read on this forum that 20mV/div is "useless to see PSU ripple/noise". Not sure if that really holds true. 20mV/div is the published input sensitivity of hantek PSO 2020. Hantek 6022BE has 10mV/div input sensitivity (about $70 on aliexpress). Gyro's recommendation, OwonVDS1022 has a published input sensitivity of 5 mV/div ( $85 on aliexpress for the non-isolated version, $116 for the isolated version VDS1022i) I don't think your budget will allow for any oscilloscope with 1 mV/div input sensitivity

I  think Owon VDS1022(i) is probably better for you than Hantek 6022BE for a little price difference. Also, Hantek is well known for their dubious specs.

You could be interested in Gyro's excellent thread about Owon VCS1022i
https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/

Dave's video about "How To Measure Power Supply Ripple & Noise" has very good info and tips about what you are aiming at, I think


 
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Online BillyO

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Re: need an oscilloscope on a very low budget
« Reply #13 on: December 06, 2022, 04:13:11 pm »
@sx57.

The Hantek 6022BE is not a great scope.  There are huge limitations and it does not even meet it's rate 20MHz bandwidth.  It's is more like 15MHz at the very best.

However, the Hantek 6074 is a much, much better scope.  Yes, I know it is $150, but compared to the 6022BE is is worth it.

Here are a short list of the advantages:

Has AC coupling
Has 4 channels
Exceeds it's bandwidth rating ** (see below)
Comes with two x1/x10 probes and two alligator clip cables.
1GSa/s - (20 times better than the 6022BE)
More trigger modes (edge, pulse, video, alternate)
Greater vertical sensitivity range 2mV to 10V  vs 20mV to 5V

** When used with only 1 channel enabled it has 250MHz bandwidth!!  This decreases as you add channels until you have all 4 enabled where it still delvers better than 80MHz bandwidth.


My advice is to save up a few more $$ rather than throw your money away on the 6022BE
Bill  (Currently a Siglent fanboy)
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Want to see an old guy fumble around re-learning a career left 40 years ago?  Well, look no further .. https://www.youtube.com/@uni-byte
 
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Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #14 on: December 06, 2022, 08:48:49 pm »
thanks a lot for your great assistance my friends. i no longer consider 6022be as it has a very bad reputation as you have clearly pointed out. i will save money to buy a better scope like owon or hanek 6074.i am still interested to hear more from you about hantek 6074bd,OWON VDS1022 or any other suggestions you may have.
OWON VDS1022 is between 120 to 160 dollars here while hantek is about 220 to 256 dollars.do you think the owon is good enough or should i save for the hantek 6074bd or something else?
« Last Edit: December 06, 2022, 08:54:28 pm by sx57 »
 

Online BillyO

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Re: need an oscilloscope on a very low budget
« Reply #15 on: December 06, 2022, 11:37:14 pm »
I was mentioning the 6074BC.  It is here for $153: https://www.ebay.ca/itm/291742464153

The Owon shares a lot of the issues with the Hantek 6022 (2-ch, low bandwidth, low sampling rate).  I think you will grow out of it quickly.

« Last Edit: December 06, 2022, 11:40:32 pm by BillyO »
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Offline donlisms

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Re: need an oscilloscope on a very low budget
« Reply #16 on: December 06, 2022, 11:40:49 pm »
An alternative to finding an oscilloscope that can directly interpret your power supply "signals" would be to use an appropriate amplifier, to make the signal easy for the oscilloscope to show.  I think an AC coupled amplifier with sufficient gain, even a simple one, could do the job.  Lots of gain for the ripple and noise, no gain for the DC. This preamplifier should be low noise itself, of course!
 
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Offline tatel

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Re: need an oscilloscope on a very low budget
« Reply #17 on: December 07, 2022, 01:37:54 am »
Now you are about to get analysis paralysis. It's knocking at your door. Don't let it get in.

USB scopes are recommended only when you can't afford an entry-level 4 channel benchtop scope or have some special portability needs. If that's the case, it seems most people think Owon VDS1022 is the worthiest one. There's no point purchasing a "more capable" USB scope if a cheaper one can do what you need it to do. The "more capable" one will remain always an USB device and it will always have the shortcomings of an USB scope.

Please note I am lucky enough to have one of these benchtop 4 channel scopes in the $500 range, so I don't have any user experience with USB scopes. I think Owon VDS 1022 could do all you need it to do, but you'll have to check it yourself.

Now, to make your decision, there are some pointers:

Dave's video explains, much better than most of us could ever do, what you need to measure PSU ripple/noise. Do you think VDS1022 is able to do what Dave says in that video? Check the specs. Has it enough bandwidth? Enough channels? Enough sensitivity?

Go to Gyro's  thread. Is people happy with Owon VDS1022? What do they say about how it works? How do they compare it with other USB devices? You should search the forum for threads about the different candidates. Only you know what device you can really afford.

If you read Gyro's thread, you'll find there is people who purchased the non-isolated version and converted it to the isolated version afterwards. It doesn't seem to save much money, but if your budget is so tight, it could allow you to make your initial expense lower while retaining the ability to upgrade in the future. Many purchased the non-isolated version, seem to be happy with it, and do not feel any need to upgrade to the isolated version.

You'll find also that many owners of Owon VDS1022 are using an unofficial software which seems to solve some shortcomings the official one has, see https://github.com/florentbr/OWON-VDS1022

Owon VDS1022 is Dave's recommendation if you have to put together an electronics lab for just $300 in all. See:

See what Dave says about USB scopes when you don't have to squeeze your wallet so much (go to 3:06 if you want but the whole video is worth watching):

You just need some hours of reading posts and to watch some videos, not just about VDS1022, but also about any other device you could be interested in. I think you have now enough pointers to do an informed decision, which can only be made by you.

It would be a little bit bizarre if, being you the prospective buyer, would be also you who doesn't read the relevant threads nor watch the dedicated videos, don't you think so?
 
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Online BillyO

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Re: need an oscilloscope on a very low budget
« Reply #18 on: December 07, 2022, 02:33:47 am »
USB scopes are recommended only when you can't afford an entry-level 4 channel benchtop scope or have some special portability needs. If that's the case, it seems most people think Owon VDS1022 is the worthiest one. There's no point purchasing a "more capable" USB scope if a cheaper one can do what you need it to do. The "more capable" one will remain always an USB device and it will always have the shortcomings of an USB scope.

...

I don't have any user experience with USB scopes.

The fact is, the Owon VDS1022 is maybe the "worthiest" 25MHz USB scope.  Nothing more.  There are in fact USB scopes, with all the shortcomings (?) that implies, that will put the very best $500 benchtop 4 ch. scope to utter shame.  Just check out the Pico Technology 9300 or 9400 series USB scopes .. for fun.  They run about $40,000.

What it boils
down to is, any scope is better than no scope.  However, "just good enough" is usually not the way to go as your needs are likely to change.  It is always better to go with something that somewhat exceeds your minimum requirements so you are not in a position to have to trade up in short order.

But I agree with our learned friend.  Check out some user discussions, reviews on-line and youtube videos before making a final decision.

« Last Edit: December 07, 2022, 02:39:35 am by BillyO »
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Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #19 on: December 07, 2022, 10:30:26 am »
thanks everyone for your help.

@tatel:

i had seen dave's excellent video about how to measure ripple and i had read  about smps ripples and noise. but in the end i got a little confused, on the one hand i have read that 20 mhz must be selected for ripple and noise measurement and on the other hand there was a thread that people said that there may be a mess way beyond 20mhz that we will miss if we choose 20mhz bandwidth. i also learned that 5mv/div is enough for me because a good smps should have around 10mv ripple so lower than 5mv is not gonna be that important but i was worried that owon may be lying about it's specs. i was also confused about real bandwidth needed because if 20 mhz is not enough, why should we limit it to 20 mhz to filter he higher bandwidth noise? that's when i thought asking good people of eevblog will help me to find a good solution and they will tell me if the bandwidth is low or owon is lying like hantek or any other matter i need to know. i am gonna watch the other videos posted here.
 

Offline sx57Topic starter

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Re: need an oscilloscope on a very low budget
« Reply #20 on: December 07, 2022, 10:32:14 am »
I was mentioning the 6074BC.  It is here for $153: https://www.ebay.ca/itm/291742464153

The Owon shares a lot of the issues with the Hantek 6022 (2-ch, low bandwidth, low sampling rate).  I think you will grow out of it quickly.

unfortunately,6074c is not available in iran
 

Offline Doctorandus_P

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Re: need an oscilloscope on a very low budget
« Reply #21 on: December 08, 2022, 08:51:33 am »
With USB scopes, the usability of the software is a big concern. Picotech likely has the best software and their most affordable scope is the 2204A for EUR140, which is also in your price range.
https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview

Some of the entry level handheld scopes are also in that price range. Something similar to a Hantek 2D72 or OWON HD272S.

 
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Online Gyro

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Re: need an oscilloscope on a very low budget
« Reply #22 on: December 08, 2022, 10:29:01 am »
I doubt whether the Pico will be available to the OP.
Best Regards, Chris
 

Offline Doctorandus_P

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Re: need an oscilloscope on a very low budget
« Reply #23 on: December 08, 2022, 02:22:46 pm »
I doubt whether the Pico will be available to the OP.

Same here, but If I don't post it because of my doubt then the door is already closed beforehand.
 

Offline tatel

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Re: need an oscilloscope on a very low budget
« Reply #24 on: December 08, 2022, 03:20:48 pm »
The fact is, the Owon VDS1022 is maybe the "worthiest" 25MHz USB scope.  Nothing more.  There are in fact USB scopes, with all the shortcomings (?) that implies, that will put the very best $500 benchtop 4 ch. scope to utter shame.  Just check out the Pico Technology 9300 or 9400 series USB scopes .. for fun.  They run about $40,000.

You are right, of course. I just disregard top ranking USB scopes because OP says he has a really tight budget. AFAIK, any USB scope in that price range will probably suffer from USB bottleneck. That Owon seems to be able to do most of the work within the device itself, so it seems to work better than others, while using just full speed USB. Other devices using high speed USB 2 (so theoretically 40x faster) seem to work worse. Please correct me if I'm wrong, I'm always willing to learn.

My point is: should OP wait until enough money is saved to get a tool more than good enough, his project would have to wait also. Getting a good enough tool as soon as posible, he can go ahead with his project sooner rather than later. And he can always continue savig after the purchase, while having a working project.

@sx57 I'm guessing this stuff is heavily taxed in your country?
 
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