Which oscilloscope and/or logic analyser?

[spec]

I used to think the same way, but times have changed. I had set up my latest hobby bench, years ago, with two scopes, the analog one an HP 1725A 275MHz scope and the digital one was a low cost Rigol 50MHz unit. Over a few years, I used the analog scope less and less until it basically just collected dust, while the inexpensive Rigol digital unit did everything I needed to do. Then I upgraded to a Rigol DS2202 digital scope and never looked back. I've still got the 1725A, but it sits on a storage shelf. Nowadays, a beginning hobbyist, with limited budget is probably better off buying one of these sub-$400 digital scopes brand new rather than buying an old, retired Tek or HP analog scope. It also becomes imperative that the new user study and understand the aliasing problem and sampling limitations inherent in such a device. I would recommend to the beginner a minimum spec of 1GSample/second and the more the better.
Although I don't get out to commercial labs as much as I used to since retiring, none that I've seen use analog scopes anymore, but they do spend good money on high performance digital units like 10Gsa/sec and so on.

Hmm. nicely put RR,

I did imply that a traditional scope was more emotion than sense.

A good 1 GHz sampling scope (with an implied theoretical absolute maximum bandwidth of 500 MHz) would be nice, but very expensive I would think.

And, of course, it depends on what kind of electronics you do.

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[spec]

better still, there are some osci kits on ebay for AUD70 or so

What sort of performance would you get for that price?

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[case-sensitive]

no idea, but its only the PCB board and the LCD screen. No housing and nothing, so may well be the AUD350 creature just the main ingredients. I think an USB osci was about AUD 80 or 90. Runs of USB power, no screen and much else. So I guess there is not much to a low budget digital osci anymore.

 

[earckens]

tried a digital scope at the shops, has the same amount of self induced noise if you crank it up (max frequency, max amplification) as a CRT one (I was thinking its the probes or the rotten contacts on my old one). CRT one has way sharper lines and unlimited resulution (not 480 x 640 pixels).
USB one would be fun, full screen resolution and way cheaper

What do you define as a "digital scope": can you give an example? And what is the difference with an USB scope to you?

 

[Veraxis]

I did imply that a traditional scope was more emotion than sense.
...And, of course, it depends on what kind of electronics you do.

I would agree that DSO's are generally the better option these days, especially for digital applications. The ability to store one-shot waveforms in memory makes them massively superior to analog storage for measuring digital signals and analog transients. A lot of DSOs also have other data processing features such as an FFT mode to look at the signal in the frequency domain, effectively turning it into a spectrum analyzer, albeit with relatively high resolution bandwidth and lower dynamic range compared to a proper frequency-swept SA.

For repetitive waveforms both are perfectly usable. I have heard arguments going both ways saying that analog or digital scopes have more or less noise, but I'm not really convinced that there is much difference. The noise on a DSO looks different due to the quantization of the trace. DPO-type scopes with variable brightness from averaging multiple traces do a good job of simulating the "softer" looking noise of an analog scope, but they tend to be expensive. Either way, the noise is still there.

The only area where I think that an analog scope has a noticeable advantage is in X-Y mode, as an analog scope does not rely on sampling-- the deflection plates in a CRT make it a natural X-Y display. Additionally, many DSOs do not take an external Z or blanking input, which can make it difficult to view video signals in X-Y mode. The quality of the X-Y mode in a DSO will depend a bit more on the exact model in question.

 

[spec]

A lot of DSOs also have other data processing features such as an FFT mode to look at the signal in the frequency domain, effectively turning it into a spectrum analyzer, albeit with relatively low resolution bandwidth and dynamic range compared to a proper frequency-swept SA.

Hmm- interesting.

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[case-sensitive]

What do you define as a "digital scope": can you give an example? And what is the difference with an USB scope to you?

https://www.jaycar.com.au/25mhz-dual-trace-digital-storage-oscilloscope/p/QC1932 this one I tested at the shops, can get a 100MHz at ebay for less
USB scopes for AUD100 at ebay:
Hantek 6022BE PC-Based USB Digital Storag Oscilloscope 2 Channels 20MHz 48MSa/s
PC USB 2CH 20M Digital Oscilloscope 48MS/s + spectrum analyzer + data recorder A
had a look at the kits, start at AUD30, but 1MSPs means 100kHz, pretty pointless. Maximum 2MHZ for about AUD100. So, no.
I see, the other 2MSPs gets 1Mhz, so 2 samples per wave, not too accurate.

 

[Nigel Goodwin]

start at AUD30, but 1MSPs means 100kHz, pretty pointless.

Not at all, you can do a hell of a lot with a 100KHz scope - so not 'pointless' at all.

I've recently built one of these:

www.banggood.com/Orignal-JYE-Tech-DS0150-15001K-DSO-SHELL-DIY-Digital-Oscilloscope-Kit-With-Housing-p-1093865.html

I find it very useful, makes a worthwhile addition to my Rigol DSO and pair of analogue scopes.

Generally the higher spec the better, but a huge leap in specification only really provides a fairly small leap in usefulness.

 

[case-sensitive]

I guess 200kHz will do for audio, am lucky if I can hear 15kHz. and all that weird stuff it shows at 20MHz and 5mV/cm, its there with and without probe attached. The buzz in my speakers is really annoying (maybe same level as a mozzie), but I cannot see anything in the osci. If I cannot quantify it somehow its really just try something and listen. Would be easier to disconnect the speakers and measure something.

 

[earckens]

Not at all, you can do a hell of a lot with a 100KHz scope - so not 'pointless' at all.

I've recently built one of these:

www.banggood.com/Orignal-JYE-Tech-DS0150-15001K-DSO-SHELL-DIY-Digital-Oscilloscope-Kit-With-Housing-p-1093865.html

I find it very useful, makes a worthwhile addition to my Rigol DSO and pair of analogue scopes.

Generally the higher spec the better, but a huge leap in specification only really provides a fairly small leap in usefulness.

What applications do you use it for? I may be wrong but for normal microcontroller applications that would not be sufficient (ie 10 to 50MHz operating frequencies)?

 

[case-sensitive]

I may be wrong but for normal microcontroller applications that would not be sufficient (ie 10 to 50MHz operating frequencies)?

with 1MHz sampling rate the air is getting thin for 10MHz applications. For audio which ends at 20kHz its sufficient. If something happens at 80kHz, 20kHz is 2 octaves down and human hearing at 20kHz is pretty limited... HiFi definition initially was up to 10kHz and hearing test at a factory is to 8kHz or so, pretty useless for audio

**broken link removed**

12 bit vertical resolution, howsat. The others have 8. AUD22 for the kit and another 10 for the housing

 

[earckens]

On Eevblog there is an interesting discussion about same subject: https://www.eevblog.com/forum/testgear/hantek-dso5000p-decision/ ..there seems some concern about Hantek quality (problematic firmware), and there is an interesting reference to Rigol scopes. As already pointed out here sampling rate should be a minimum 1Gsa/s, regardless of frequency. And I can indeed see a higher correlation between price and sampling rate then between price and frequency.

What surprises me too is that a Rigol DS1054Z -which is a very decent 4 channel 1Gsa/s 50MHz scope can be bought cheaper in Europe then via Aliexpress or Banggood in China: excl. TVA about 330, in China about €470 incl. shipping but with the risk of customs charges.

 

[Nigel Goodwin]

What applications do you use it for? I may be wrong but for normal microcontroller applications that would not be sufficient (ie 10 to 50MHz operating frequencies)?

It would be unusual to need 50MHz for microcontroller applications, as the high frequencies are the internal clock rate, which you can't access, and even with an external crystal would rarely have any need to check it.

It's crazy not to have a scope at all just because you can't afford an expensive one for the very rare occasions you might need it.

Most signals on microcontrollers are relatively low frequency, so easily covered by audio range performance.

So 'normal' microcontroller use only calls for a low frequency scope, other than on very rare occasions.

I've recently been using my Rigol, actually for measuring the SPI clock frequency I'm using - but it requires nowhere near 50MHz to do that.

 

[spec]

For audio which ends at 20kHz its sufficient.

Afraid it is not quite so simple.

With audio amps you can get oscillations from 2MHz to around 6MHz, and with MOSFETs the sky is the limit.

You can also get artifacts at any frequency: x over distortion for example.

Even taking the highest audio frequency of 20KHz, many audio amplifiers respond to 100KHz and higher, which means that 100MHz is only two decades higher. So if you are investigating/designing frequency stability a scope with a high frequency response is essential.

Then there are class D audio power amplifiers, which involve relatively high switching frequencies.

Plus, there is a host of other aspects in audio work especially when you get into the digital audio field.

With scopes of any breed, I have found that the critical factors are frequency response, resolution, low noise, and good triggering, assuming of course that all the fundamentals are in place: reliability, accuracy, ease of use.

You can't always go by paper specifications and, say a Tektronix scope with an equal specification to a lesser make, will have a far superior performance in practice.

A scope may have a stated frequency response but what happens at higher frequencies; with one scope the response may drop like a brick, but with another scope the response may drop gracefully at unit slope- there is a vast difference between the two. Also, some scopes do not even meet their stated frequency response and/or are not flat in their pass band.

Just to make it clear- I am not trashing any scope however humble, and the scopes that I used when an electronics newbee were very humble but still extremely helpful in investigating practical electronics.

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[earckens]

I've recently been using my Rigol, actually for measuring the SPI clock frequency I'm using - but it requires nowhere near 50MHz to do that.

Nice to read your comment, I am learning every day here. What MCU's do you mainly use? Did you never feel the need to use a logic analyser on items like SPI?
Edit: I read your signature url, now I understand

I recently set up my new-old Tektronix to verify signals on ultrasonic sensors and I find it amazing what you can get out of a classic analog scope. I know from this thread now that there is quite a difference in usage/application/limitations between analog and digital scopes but as JLNY said earlier I will get acquianted with my purchase first and then as time goes by and I get more knowledge about possible digital scope alternatives start to look further there.

 

[Nigel Goodwin]

Nice to read your comment, I am learning every day here. What MCU's do you mainly use? Did you never feel the need to use a logic analyser on items like SPI?

My main 8 bit one is the 16F1827, which is an enhanced 14 bit series device. But I've fairly recently started using the 16 bit 24FJ64GA002 for the extra speed, facilities, and particularly memory space. Both devices have internal clock oscillators making them simple to use, saving any messing about with crystals etc.

As for logic analysers, I have a USB one, but haven't ever used it - I've not really had any occasion to - particularly as my Rigol scope is sat 9 inches from my left elbow at this very moment, so it's much easier to use that.

 

[Nigel Goodwin]

Afraid it is not quite so simple.

In practice it pretty well is

You make some valid points, but they are all extremely minor - and only of any concern in a tiny number of rare occasions.

ANY scope is extremely useful, and higher spec ones are marginally better - but it's only rarely a concern.

 

[earckens]

ANY scope is extremely useful, and higher spec ones are marginally better - but it's only rarely a concern.

The diy kit you referred to earlier has just one channel which in my opinion seriously limits its usefulness for any serious work.

 

[Nigel Goodwin]

The diy kit you referred to earlier has just one channel which in my opinion seriously limits its usefulness for any serious work.

For it's cost it's extremely useful, and far better than no scope at all.

Certainly double beam is useful, but you probably only use the two beams in far less than 10% of occasions.

And to be honest, you probably don't 'need' two beams on many of the occasions you use them, it just makes it more convenient - often you use one of the beams for sync, and the other for actually viewing, which you can do on most single beam 'proper' scopes.

 

[spec]

In practice it pretty well is

You make some valid points, but they are all extremely minor - and only of any concern in a tiny number of rare occasions.

ANY scope is extremely useful, and higher spec ones are marginally better - but it's only rarely a concern.

As I said, it depends what you do.

I would not agree that they are minor points let alone, extremely minor.

I did not say that any scope was not useful. What we are discussing is the characteristics of a scope for all around use.

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