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Author Topic: Best oscilloscope choice?  (Read 39672 times)

Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #45 on: January 23, 2016, 09:53:44 AM »
2) the U.S. Education spares no expense on getting the good stuff.
when a school upgrades their equipment theres usually 30-50 scopes that get sold out the back door.
ive gotten a few this way over the years.

Surplus, yes, they sell old oscilloscopes in official auctions or something. These are mostly ones from 1980's, at least 20 MHz and two channels. Positive about that, is that they sell them cheaply, because they sell many of them, and thus really have no time to test whether they work or not. These scopes often end up in ebay, and the sellers also don't test them very thoroughly, as they sell many of them. So when seeing that the oscilloscope is one of such, there is a good chance to get an oscilloscope cheaply, which is better than its price may indicate. What shows that they may be some of these, is when they sell several oscilloscopes of the same type at once. I think my oscilloscope may also be one of these, as the seller in ebay sold two oscilloscopes of exactly the same type. And the other things, such oscilloscopes are sold quickly, thus they mostly are not cleaned at all, so another indication is that the oscilloscope is not made shiningly clean. Finding that it is one of these oscilloscopes, increases the trust that the seller doesn't try to cheat you with a scope that is worst than shown.

So indeed, the best option is to get some 20 MHz 2 channel oscilloscopes from 1980's. This may also be the cheapest option, because there is the biggest supply of these. I have always thought that, i told about the less powerful ones only for these who are true minimalists, and like to restore very old oscilloscopes. As this is a fun which many people cannot resist ;)

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Re: Best oscilloscope choice?
« Reply #45 on: January 23, 2016, 09:53:44 AM »

Offline Paul-R

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Re: Best oscilloscope choice?
« Reply #46 on: January 23, 2016, 05:03:46 PM »
I don't think it is worth spending a lot and buying a new scope as a first one because we learn so much with the first one bought. When we know what we NEED, by looking at blurred and indistinct scope shots, then spend the cash and get the right one.

Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #47 on: January 25, 2016, 10:18:16 PM »
Some warn against the Heathkit and Bell & Howell oscilloscopes. They especially warn against Heathkit and Bell & Howell school oscilloscopes, and old Heathkit oscilloscopes with vacuum tubes. But i found a video https://www.youtube.com/watch?v=hoAmzsz_bJY which shows that a Heathkit IO-4205 oscilloscope works  perfectly. This is a 5 MHz two channel oscilloscope made in 1980's, it is solid state, has triggering and modern probes fit to it, by schematics it can be used both with 120 V and 240 V mains power. Heathkit IO-4105 is a one channel version of it, but it has an external triggering. If true, this may be the cheapest reasonable option, because these oscilloscopes are the cheapest in ebay. Like there is one Heathkit IO-4105, that costs $53 with free shipping to America http://www.ebay.com/itm/Heathkit-Oscilloscope-10-4105-Working-Unit-Ships-FREE-/281908425196?hash=item41a30d31ec:g:mEsAAOSwJkJWlpeo , this one has though only a dot on the screen, but is said to be "in good overall working condition".

Some what they call school oscilloscopes, are Heathkit IO-4540, which is also named Bell & Howell I0D-4540. Heathkit and Bell & Howell oscilloscopes often seem to be completely identical, often with the exact same numbers. These look like completely identical to Heathkit IO-4105, but they are warned against and thus may not be the same inside. I found only one video in youtube about such oscilloscope, and it showed what was said to be its own calibration signal. This supposed to be sine, but it was a kind of distorted, weirdly angular. Maybe the oscilloscope's calibration signal was bad, maybe the distortion was caused by the oscilloscope, but whatever the case, it indicates a low quality of the oscilloscope. So for these reasons these oscilloscopes likely should be better avoided, in spite that they cost less in ebay than Heathkit IO-4105.

Perhaps this is all i could say about buying old oscilloscopes, from the little knowledge that i have. Hope it was anyhow useful for anyone.

Free Energy | searching for free energy and discussing free energy

Re: Best oscilloscope choice?
« Reply #47 on: January 25, 2016, 10:18:16 PM »
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Offline TinselKoala

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Re: Best oscilloscope choice?
« Reply #48 on: January 26, 2016, 06:04:32 AM »
And now... RM503 and the Four Oscillators present:  Lissajous for You #2  (Best of)

http://www.youtube.com/watch?v=q55-CTCd2k4

Offline Nink

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Re: Best oscilloscope choice?
« Reply #49 on: January 26, 2016, 06:12:19 AM »
And now... RM503 and the Four Oscillators present:  Lissajous for You #2  (Best of)

http://www.youtube.com/watch?v=q55-CTCd2k4

Beautiful

Free Energy | searching for free energy and discussing free energy

Re: Best oscilloscope choice?
« Reply #49 on: January 26, 2016, 06:12:19 AM »
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Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #50 on: February 02, 2016, 09:56:16 AM »
Yes these Lissajous were really beautiful. This was an old tektronix with vacuum tubes, i guess, some of these are very precise instruments.

From my little knowledge, i try to explain how these old repetitive sweep oscilloscopes work, also called recurrent sweep oscilloscopes. Because these who may think about buying such old oscilloscope, should have some idea of what they get.

They made recurrent sweep oscilloscopes already in the 1940's and maybe even before. These made in 1940's look almost exactly like Eico 460, though they sold Eico 460 until 1976 or such.

These oscilloscopes were generally made before the triggering oscilloscopes. All i know about how they work, they say they feed a small amount of the input signal, to the horizontal sweep oscillator. I don't get a clear idea of how it works from that, but i understand that this somehow enables to synchronize the horizontal sweep oscillator, with the external signal, so the horizontal sweep frequency becomes some harmonic of the input signal frequency.

I noticed that recursive sweep oscilloscopes have a scale on the horizontal scale fine tuning knob, which triggering oscilloscopes almost never have. So i guess, you change the horizontal frequency, until luckily the signal on the screen stops for a moment. Then from that scale you can calculate frequency, though it is likely not very precise. Or some maybe enabled to find a Lissajous pattern with the external signal. Or you find frequency with an external function generator and a Lissajous pattern, if you luckily have one.

Then you switch to internal synchronization, turn the horizontal frequency knob again, and luckily can get the signal to stay still on the screen. Then, knowing the frequency before, it is possible to calculate the times. From the oscilloscope's settings at that time, it is not possible to find frequency, because the frequency is unknown, and depends on the frequency of the signal. Some simpler oscilloscopes, i understand, had a very slight internal synchronization, so no switch to switch it off, but they synchronized at the frequency very near the signal's frequency, so with some rough approximation, it was also possible to find the frequency.

It is also possible to synchronize with the external signal, like Eico 460 can do that. This is why on these scopes, the input is called external sync, not external triggering. And on this sinometer oscilloscope, it is also ominously called external sync. That way it should be possible to compare two signals, when the frequency of the external sync is known. Because it should synchronize always the same way then, the synchronization only depends on the external sync, and not on the input signal. Thus it should also be possible to measure a phase difference. Or that can be done with Lissajous, which is difficult or impossible though, when the shape of the signals is too complex.

Thus it may be possible to measure time characteristics with the recurrent sweep oscilloscopes, but this is much more difficult, inconvenient and much more imprecise, compared to the triggering oscilloscopes. If precise measurements of time characteristics are necessary, then these oscilloscopes may be useless for the task. The recurrent sweep oscilloscopes, when they were good, were very good for certain tasks, but not for others. This is why they were sold a long after the triggering oscilloscopes were widespread, as a "maintenance class" oscilloscopes.

This sinometer oscilloscope also may be a recurrent sweep oscilloscope, not a triggering oscilloscope. So this may be an additional pain, in addition to ways how it is a scrap otherwise. I'm telling this because i know that it is difficult to convince some to not to buy that sinometer oscilloscope, as it looks so appealing. This oscilloscope is an example of the new wave of chinese scrap products which start to enter the market. Be cautious about these, as they often are not what they look, or are believed to be. I mean, some of the cheap things they make, are still useful, but at one point they may become useless, or likely will, considering how the things develop further, and more "innovations" are added.

Offline TinselKoala

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Re: Best oscilloscope choice?
« Reply #51 on: February 02, 2016, 10:32:40 AM »
Determining frequency using the RM503 precision low-frequency oscilloscope:

http://www.youtube.com/watch?v=teXXF0a_WoI

Displaying a stored waveform from an analog oscilloscope:

http://www.youtube.com/watch?v=HcHg5gGB5xk

 ;)

Free Energy | searching for free energy and discussing free energy

Re: Best oscilloscope choice?
« Reply #51 on: February 02, 2016, 10:32:40 AM »
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Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #52 on: February 02, 2016, 01:12:46 PM »
Displaying a stored waveform from an analog oscilloscope:

http://www.youtube.com/watch?v=HcHg5gGB5xk

 ;)

Yeah that's clever, but... I figured out something else. It is possible to use gschem, to draw waveform, and as it is a vector graphics editor, then its file is easy to use for all kind of calculations, like with using python. That way it is possible to easily calculate power, from the waveforms of voltage and current. Power is still V * I, but all is about calculating the average power.

And, pretty sure there is software, that is capable of transforming a picture into a vector form. Or calculations can be done directly from a bitmap form as well, but better if it were a bit normalized, like lines made to a single pixel. But all that is a too high tech for me, i stick to gschem, and do it manually. ;)

Offline TinselKoala

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Re: Best oscilloscope choice?
« Reply #53 on: February 03, 2016, 08:17:40 AM »
Back in the "good old days" we would tape some tracing paper on the scope screen, transfer the scopetrace with a pencil, then cut out the waveform areas carefully with scissors and then weigh them on an analytical balance. This method can be surprisingly accurate if you do a little calibration testing beforehand.

Free Energy | searching for free energy and discussing free energy

Re: Best oscilloscope choice?
« Reply #53 on: February 03, 2016, 08:17:40 AM »
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Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #54 on: February 03, 2016, 03:49:44 PM »
This is not an easy task, to take an image, and transform it into curve, which then can be used for calculations. I tried to find a software which transforms an image into such curve, i couldn't find. I tried to transform the picture in gimp, the difference of gaussians, etc, give an outline of the trace, two lines, but none are one pixel thick, and it is impossible to eliminate all the background dots. Thus such image cannot be used for calculations. So still it has to be done manually. Like load the image to gimp, then create a transparent layer, and draw to it one pixel dots. Then save that layer as xpm, which then can be converted to a table of numbers, and then some curve fitting program can be applied to it. There are many these. This method can provide very accurate results, and very nice graphs, but it's quite a work.

So i still stick to this manual drawing with gschem, mostly quite rough approximation is enough. Or when one wants to do it better, one may do it with inkscape or such, where i think too it is possible to add a transparent layer, and save it hopefully in some very simple vector graphics format, which then can be used for calculations, or then as a data for curve fitting.

Now does anyone understand what i'm talking about?

Offline TinselKoala

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Re: Best oscilloscope choice?
« Reply #55 on: February 04, 2016, 11:15:46 PM »
This is not an easy task, to take an image, and transform it into curve, which then can be used for calculations. I tried to find a software which transforms an image into such curve, i couldn't find. I tried to transform the picture in gimp, the difference of gaussians, etc, give an outline of the trace, two lines, but none are one pixel thick, and it is impossible to eliminate all the background dots. Thus such image cannot be used for calculations. So still it has to be done manually. Like load the image to gimp, then create a transparent layer, and draw to it one pixel dots. Then save that layer as xpm, which then can be converted to a table of numbers, and then some curve fitting program can be applied to it. There are many these. This method can provide very accurate results, and very nice graphs, but it's quite a work.

So i still stick to this manual drawing with gschem, mostly quite rough approximation is enough. Or when one wants to do it better, one may do it with inkscape or such, where i think too it is possible to add a transparent layer, and save it hopefully in some very simple vector graphics format, which then can be used for calculations, or then as a data for curve fitting.

Now does anyone understand what i'm talking about?
I certainly do. Back in the "Ainslie" day, I demonstrated how to do this process manually from a good photo of an oscilloscope trace. It is very tedious, takes about 4 hours to process a single image that way. But the results are accurate enough to be able to make valid conclusions.
I also used another technique to determine areas under a curve using pixel counting.

Now, of course, thanks to the generous donations of some forum members, I have an oscilloscope that does this math integration automatically for me.

Free Energy | searching for free energy and discussing free energy

Re: Best oscilloscope choice?
« Reply #55 on: February 04, 2016, 11:15:46 PM »
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Offline conradelektro

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Re: Best oscilloscope choice?
« Reply #56 on: February 05, 2016, 09:51:33 PM »
I got this scope (UNI-T UTD2102CM):

https://www.reichelt.de/Oszilloskope-Spektrumanalyser/UTD-2102-CM/3/index.html?ACTION=3&GROUPID=4044&ARTICLE=123971

Is this a good scope?

I would appreciate comments from the experts.

I bought it mainly because it was easily available in my part of the world. The price measured against it's capabilities was reasonable. And it is totally modern and can also be connected to the PC via USB. So, it is a fully functional stand alone scope or it can be handled like a PC-scope with a program running on a PC.

It can also store images on a USB-stick. Funny enough, the capacity of the USB-stick should not be more than 8 GB, otherwise the scope behaves strangely when trying to store an image file on it. It seems to be the supported file system.

One can argue, that the knobs and keys are not as rugged as on highly priced scopes (e.g. from TEKTRONIX).

When I looked (about three years ago), a very good scope would have costed EUR 1500.-- and more.

And yes, it is a very steep learning curve to use a scope properly. But the modern digital scopes are more forgiving than the older analogue ones. Specially the storage capabilities are very helpful. Also the mathematical functions help a lot.

The scope becomes outdated if looking at fast computing equipment. Even microprocessors are running now beyond 1 GHz. One needs 32 channel logic analysers or mixed signal scopes (12 GHz sampling rate)  to see what is happening on a 3 GHz bus:

https://en.wikipedia.org/wiki/Logic_analyzer

Greetings, Conrad

Offline Paul-R

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Re: Best oscilloscope choice?
« Reply #57 on: February 10, 2016, 06:30:33 PM »
Back in the "good old days" we would tape some tracing paper on the scope screen, transfer the scopetrace with a pencil, then cut out the waveform areas carefully with scissors and then weigh them on an analytical balance. This method can be surprisingly accurate if you do a little calibration testing beforehand.
Its a bit Barney Rubble, TK. Try a planimeter. Somewhere, there is a DIY planimeter page.

Offline Nink

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Re: Best oscilloscope choice?
« Reply #58 on: March 02, 2016, 06:06:23 PM »
I had a 200Mhz Tektronix 475 about 20 years ago I left back in Aus.  Looking to buy a scope and the 475's seem to be selling ~ $300 US on ebay without probes and  that seems reasonable .  Is anyone still using these,  there seems to be a lot of them on the market but I didn't want to buy something that fails 2 weeks later, overheats, knobs break etc. Anything to look out for when buying one, any models, years to stay away from. Was thinking a 475 (200MHz, 2mV/div)  or 475A (250MHz,  5mV/div). 


Offline ayeaye

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Re: Best oscilloscope choice?
« Reply #59 on: October 14, 2016, 09:18:26 PM »
The thread about how to measure power with analog oscilloscope is now there  http://overunity.com/16911/measuring-power-with-analog-oscilloscope/#.WAFXS7Np_iY . For using analog oscilloscope for overunity experiments, it is absolutely essential to use some method to measure power with these oscilloscopes, no matter what are the shapes of the signals. One may say that doing it in any other way than pixel counting, is "not professional" or whatever, but the same transforms of the picture of the oscilloscope screen have to be done also for pixel counting. So if one thinks that it necessarily has to be done by pixel counting, then please add to that thread the details of how to do it by pixel counting.

 

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