USB oscilloscope wanted

[Andrew Cowan]

Hi

I am thinking about buying an oscilloscope, and for my price range, a USB 'scope looks best.

After a quick search, the PicoScope 2203 turned up best, at £159. Does anyone own one or know of a better one?

It is just for analyzing basic circuits - will 5MHz be enough?

Picoscope 2203:
5MHz
2 Channels
USB interface
1M ohm impedance
500ns to 200s per division (time)
20V max
Protected against voltages over 100V
Includes wave generator
Supports Triggers
Includes Spectrum analyser
Full specs:
http://www.picotech.com/picoscope2200-specifications.html

I don't know anything about oscilloscopes - so does this one look like it is a nice one?

Times in the past I wish I had had one:
Checking signal from oscillators
Checking servo signals
Checking power supplies for smoothness
etc.

Could this one do that kinda thing?

Thanks,

Andrew

 

[Dippy]

Uh oh! This will now start the my-favourite-scope thread.

There have been numerous threads and digressions on this subject.
In fact almost as many as there are types of 'scope.
I won't mention my 2 scopes that I use as you want a USB based one.

You will get many suggestions but DO be aware that some USB 'scopes from not-so-famous brands have pretty slow sample rates.

Although not the cheapest, PICO have a good reputation generally though apparently there have been some Forum moans. But, on the other hand, if they sell 10,000 and 20 people moan (of which 60% will be inexperienced newbies) then that is pretty good I'd say. It wouldn't worry me.

Also, with PICO (and poss others), you can get them specially calibrated. This costs, but certainly means that they are good enough to calibrate. This is unavailable to some a.n.other brands and confirms the old saying 'You can't polish a turd' Just kidding, but a semi-serious point... can you trust an unknown instrument?
(Not that anyone cares when they see something on Ebay for a fiver).

Anyway, check this thread:
http://www.picaxeforum.co.uk/search.php?searchid=120411&pp=25&page=2

... and wait for the list of "mine was real cheap and is perfectly good"...

 

[Andrew Cowan]

Hooray! This will now start the my-favourite-scope thread.

Glad I made you happy.

That link you posted doesn't work (for me (says sorry no matches)). I'm glad that PICO are a good brand - that scope seems everything I want for a good price, even if that is viewed as not the cheapest.

Just so I know what is what, can someone post some things that would require an oscilloscope that can read frequencys of over 5MHz?

Also, is a frequency generator still useful even if it can only make +-2V?

Thanks,

Andrew

 

[Dippy]

I'll reply to keep your thread bumped to get input from others...
Sorry, that link went funny I must have copied the wrong thing. I just got it from one of the many search results from *scope. It was a thread from a couple of months back where people were suggesting USB scopes.
Someone (I can't remember who) got a very reasonabley priced one, but the posted pictures appeared to show aliasing (or they didn' set it properly as it was a new toy). Not good if aliasing.

"...that would require an oscilloscope that can read frequencys of over 5MHz?"

- Checking crystal osc Over 4MHz, checking MOSFET gate switching, checking quality of square wave leading/trailing edge to name but a few.

I would always suggest getting something a bit better than you need today as you don't know what you'll need in a few months and having to buy a 'better' one is uneconomic.
But then I'm good at spending other people's money!

 

[eclectic]

Andrew.

Looks like a great piece of kit.
I'm seriously tempted myself, by the 2204/2205.

But, £159 ......

Don't forget to add

Probes... say £20
Delivery ..say £15

And the hideous VAT! (unless you or your benefactor are exempt.)

e

Added. Dippy is exactly right.
Don't spend any money yet.
Think what you might need in 2/3 years. (University ?....)
Then, later, buy the upmarket verson.

 

[higgeh]

im gonna put on my sensible hat

is it worth putting out so much money when your only checking a couple of signals

i got a shitty old oscilloscope and it does the job. jus get something simple.

 

[Andrew Cowan]

Ouch - rises to £192 including that darn VAT and economy postage. I can get probes cheaply from somewhere else.

So, what do you think? I'm 16, and about to start doing AS electronics, then I will do electrical engineering at university. Should I get this one (right at the top of my price range), or nothing (wait until I have more money)? Currently I only want to check a few signals, but in the future, I may want to check more.

I a nutshell, although that one is fine for my current needs, do you think that when I am at university and working with more complex circuits I will want a better one? If so, I won't get one now.

Thanks,

Andrew

EDIT:
I've found a company that sells surplus and second hand oscilloscopes - http://www.stewart-of-reading.co.uk/Oscilloscopes.htm Do you think a good old 'Normal' 50MHz oscilloscope is better than super 5MHz USB one?

Alternativly, I could pick up a £40 20MHZ scope for me to mess around with now, and then I could buy a proper one when I go to university. What do you think? That place looks better than ebay - they say they test all equipment, and it can be calibrated for an extra cost.

Andrew

 

[Dippy]

The spec looks good for PICO you mention. PICO are a reputable firm.
Personally, I'd go for a purpose built stand-alone BUT the USB devices have some nice features. If you want to spend >£700 then go Tektronix.

Ebay? Sorry, not for me. I want warranty and backup. I want support if there's a problem. You may be lucky. But for me (job) then I'd forget Ebay. Many will disagree.

SurPLUS stuff can be fine. My first scope was an ex-Gov Telequipment analogue storage scope circa 1807. Lasted 6 months.

You'll regret it if you don't buy a good digital storage.

 

[Ralpht]

A 5Mhz scope just won't cut it, unless your'e only going to look at audio frequencies.The PICO USB scope may be a good reliable piece of kit but it will be very limited in what it can do.
Read up on scopes and the bandwidth issues related to them. Just something as simple as the rise time of a 250millisec pulse will be hard for a 5 meg scop to display properly.

Since you are considering engineering at uni, that will mean a lot of work, not just in the uni's lab - where you will have access to 'good' test gear, but at home. You will need the best you can afford. It's a waste of money to buy a cheap one now and find that in a year or so you have outlived its capabilities. Yes - 150 is cheap for a scope.

You will be bettor off in the long run to save up and buy a 50 - 100 meg scope a few years down the track.

 

[Dippy]

Ralph:"Just something as simple as the rise time of a 250millisec pulse will be hard for a 5 meg scop to display properly"
- Mmmm.... 250mS? You may like to clarify.

But I agree on the limitations.
My cheapest/old Tektonix has a sampling rate of 1Gs/S.

But, it can't do data-logging or Spec Analysis (New Teks can do the latter).
The AWG will be useful sometimes.

Bottom line Andrew:-
1. No-one here has got one so cannot comment.
2. It is low cost.
3. PICO have a good reputation, but remember a) You won't get Rolls-Royce at Mini prices.
4. Is it good enough for what you expect to be doing next year?

The last comment has to be mixed with some common sense and financial sense.
For some of the work I do, where I'm looking at precise-ish displays of <100nS per div then that PICO would be no good.

But if most of the stuff I was doing was say audio/low-ultrasonic/IR then that PICO looks fine. It also has a good range of time-base and, believe me, sometimes a very slow setting is very useful.

On the other hand, there is no point over-spending for a spec which get's used 0.1% of the time. If your job involves looking at things then you can use the work's Tektronix or LeCroys.

And there is always the PICO 3200...
No, it's up to you.

 

[eclectic]

Gambling, but losing less.

Andrew. Another way of looking.....

In five years' time, you might buy an up-market scope.
Whatever you buy today, will by then, be effectively worthless.

£200+ or £40, for a useful learning experience.

Hmmm?

e.

 

[demonicpicaxeguy]

i recently got this http://www.hobbylab.us/default.aspx

so far i've had no problems with it,i use it mostly for looking at low speed digital signals eg debugging the sdcard interfacing problem and anything requiring a higher speed i've got a 100mhz scope
i purchased off ebay for $150,

 

[Andrew Cowan]

Thanks for all your help.

I think the bottom line is that in a few years, I'll be wanting a better scope, so I won't get that one. As that was all I can afford now, I'll save up until I can afford a better scope. Thanks!

I'll buy the picoscope 3205 or 3206 (£599 or £799), when I can afford it - in 7 or 8 years probably!

Thanks again.

Andrew

 

[womai]

Andrew,

as you may remember, I have designed a low-cost scope that people can build themselves. PC software is finished as well. I am currently traveling, but when I get back next week the final printed circuit boards and all components for a few prototypes will be waiting. It won't be a Mercedes in terms of performance, but usable for audio frequencies and a bit above (sample rate up to 1 MSample per sec, bandwidth of approx. 500 kHz, because of the sample rate usable up to maybe 150 kHz). Total material cost in small quantities is around US$70 including a pair of simple probes. Since your budget is tight and I like to support electronics education, I'd be willing to send you one at material cost plus actual shipping cost from California. Of course provided the final proto works as intended . Let me know if you are interested.

Wolfgang

 

[Ralpht]

Dippy,

Hmmm - yes 250 mS is a tad slow. A 5 Meg scope could follow that easily. I guess it helps to re-read what is written before pressing the send button....sigh! The m and n keys are too close on this keyboard - either that or "Fat finger syndrome"

I meant to say, as a random number pulled out of a hat, 250nS or faster. That will give a B/W of about 4Meg which would be up against the limits of a 5Meg scope to display correctly. The scope will be able to display the pulse train reasonably OK, but individual pulses in that train are an entirely different matter. Especially the rise/fall times of the pulse.

I was alluding to the fact that sometimes it is nescessary to look at the rise (or fall) time of a pulse, not the entire pulse itself. A limited B/W scope like the 5meg pico mentioned will not be able to clearly show the transition from lo to hi (or vis versa ) of a simple 4meg clock in a cheap and slow uP system.

Yes there are a lot of variables involved and I have been a bit simplistic, but ultimately you get what you pay for in a cheap scope. I would put that pico scope in the cheap but good audio class, but not good for digital work.

 

[Dippy]

Ralph: I was teasing slightly.

You just needed to clarifiy that you really meant a pulse which had a rise-time of whatever, in effect the pulse length/duration may be irrelevant but the leading/trailing edge may be. Anyway, I knew (roughly) what you meant, but I didn't want Newbies to think that a PICOscope couldn't measure 4Hz

No, of course it couldn't resolve a 250nS rise time. The PICO appears to have some 'unique' technicques which allow it to resolve a repetitive wave better than it's actual sampling rate. So checking a 4MHz crystal on your PICAXE would be fine. (If you don't believe me then read the full spec on-line). I wouldn't look at the bandwidth spec in isolation, as the sampling rate/s and processing come into play too.

The trouble is that NONE of us here have got one or played with one so , when it gets to specifics, NONE of us know how good it is.
I'm sure for many things it is perfectly good, but when going very fast then there is an issue. As you imply, something has got to 'give' at that price.

Horses for courses innit as usual. And you don't get thoroughbreds cheap.

Personally, and remember it's 'work' for me, I wouldn't buy anything other than big-brand stand-alone 'scope which can be calibrated. To me it's a working instrument and not just a toy to show pictures. But, if I was still at school doing lower F stuff I'd be happy with a PICO. Certainly as the product can be calibrated then it puts it in a higher league than any unknown/cheaper brands that can't.