usb scopes/logic anlysers

#1
Hi all, it's been a while since i've started a controversial thread so here goes i need to get myself a scope

and i'm considering three of my options

1, look on ebay and pay next to nothing for a used scope and probably find it's completely un suitable for what i need

2, usb scope specifically this one http://www.hobbylab.us/default.aspx
has anyone used/seen/heard of it?
or this one http://www.picotech.com/usb-oscilloscopes.html?source=Google&campaign=Osc


3,other scope's? anyone got one they can reccommend that they have used before?

the reason i'm looking at the usb scopes is mainly because i need to be able to record a "session" and the highest likely frequency i'll be looking at is 100khz
 
#2
THis will obv start the 'My favourite oscillyscope' listing.

I tried a PICO yonks ago (parallel) type. It was pretty good.
I don't know whether the new ones can do 100kHz data logging. Sample, process and send 100kHz signal would be pretty impressive if it can. Let me know too...

I now use Tektronix because I'm not tight (wallet).

The new Teks have FFT and PC connections.

A 'session'? How long is a piece of string?
Well, digital scope I use can store some, but it isn't a full blown high speed data loggers.

A quick look at Agilent scope show they have a reasonable amount of memory, but you'll have to stretch that old wallet of yours. But if your session is all day at 100kHz then you''ll be out of luck.

My personal preference is the 'all in one box' type scope, but I'm not knocking PICO as they appear to give excellent value for money.

If you go for the PICO, pls let me know how you get on, because you can't have too many scopes.

PS. I, too, wouldn't touch Ebay for something like this unless buying direct from a pukka Dealer/Distributor. I like warranties.
 
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BrendanP

Senior Member
#3
A CRO is the greatest thing since oral contraceptives IMHO

I was wondering where you had been DPG, family keeping you busy?

I read a review in Silicon Chip for a CRO from Dick Smith. They gave it a good rap so I bought one. I haven't had a 'scope before so my opinion means little. This does the job for me. Its 200Mhz/ twin trace. It was under $300 I think.

Damn, just checked, looks like they don't carry them anymore.

They've still got this real poverty pack model for $98 bucks. If times are tough it would be better than nothing.

http://dseau.resultspage.com/search...pe&sessionid=47c67ec50537beea2741c0a87f9c075e

A CRO is the greatest thing since oral contraceptives IMHO. Any of the young players on the forum would be well advised to put the screws on mum and dad for one if they can. Maybe the $98 el cheapo even.

(I just reread your post DPG, my reply doesnt really help you but other readers might be after a cheap 'scope.) Best of luck.
 
#4
i'm leaning towards the hobbylab one from canada it acording to the specs does what i want and it's a nice price

i've also downloaded the program it works with and it's very nice and straightforward with no fancy graphics... :)

my local dick smith has a 10mhz scope for $128 i think from memmory, which i'm going to get sometime down the track

i should have specified session lengths the longest likely session may get up to a couple of minutes at most

it's going to be used for debugging interface signals betweens pics avrs and various other chips

the spectrum anlyser might get a workout as well
 
#5
Fair enough, I misunderstood your requirements in your original post.

You said/typed "highest likely frequency i'll be looking at is 100khz".
I assumed/guessed that meant a , for example, 100kHz sine wave or similar.
That Hobblylab only has a sampling rate of 200kHz which will not be any good for 100kHz sine wave. (Even my home-made dsPIC scope was faster than that).

But the logic side looks OK.

It'd be nice to write a nice high-speed recorder onto SD wouldn't it.
 
#6
I've got one of those $98 ones from Dick Smith and it works fine. It depends what you want it for, and in particular whether you are doing mainly digital, or analog, or audio, or RF or switch mode power supplies or whatever. USB scope sounds like the simplest option for recording huge amounts of data.
 
#9
ok the week has come, it arrived,

i got the DISco scope from hobby lab,for $169USD
so far very impressed, the software is nice and stable still allows me to run the compiler + winamp + several copies of adobe reader + enigma browser at the same time

as advertised it's dual channel

i've attached two of the traces i did today

1 is a 20mhz crystal and the other is the 50hz mains it could pick up just by holding the probe next to the extention lead
 

Attachments

Tom2000

Senior Member
#10
1 is a 20mhz crystal...
I don't get it. How can a 200 KHz scope give you a clean display of a 20 MHz sinewave?

I looked at the scope specs on their site. I couldn't find a max frequency or sampling rate spec. By any chance are there more comprehensive specs in the manual that came with the scope that might explain what you're seeing?

Likewise, their logic analyzer spec says that they use an 8 MHz sampling rate. In the manual, do they interpret that spec? Stuff like minimum-duration pulse that it will capture?

I'd looked at that scope, briefly, in the past, but didn't pay any attention to it because of what, I thought, would be its limited frequency range. You've given me reason to take another look at it.

It sure provides a bunch of features for the money. And, since my Tek CRO is useless for debugging serial logic events, this little gizmo would be a worthwhile piece of gear to add to my home lab.

Thanks,

Tom
 
#12
I don't get it. How can a 200 KHz scope give you a clean display of a 20 MHz sinewave?

I looked at the scope specs on their site. I couldn't find a max frequency or sampling rate spec. By any chance are there more comprehensive specs in the manual that came with the scope that might explain what you're seeing?

Likewise, their logic analyzer spec says that they use an 8 MHz sampling rate. In the manual, do they interpret that spec? Stuff like minimum-duration pulse that it will capture?

I'd looked at that scope, briefly, in the past, but didn't pay any attention to it because of what, I thought, would be its limited frequency range. You've given me reason to take another look at it.

It sure provides a bunch of features for the money. And, since my Tek CRO is useless for debugging serial logic events, this little gizmo would be a worthwhile piece of gear to add to my home lab.

Thanks,

Tom
it certainly boggles the mind a little bit, hippy might have an explanation, but i'm thinking i might send them an email about it.
 
#13
Check it out DPG.
Both your piccies had mS timescales - both look like 50Hz.

A 200kHz sample rate has no chance of showing a 20MHz crystal. You may get something at higher harmonics/mulitples of the sample rate if the anti-aliasing is poor.

If that image is truly from a 20MHz crystal, and not accidental hum being picked up, then it suggests something is wrong.
 
#14
Check it out DPG.
Both your piccies had mS timescales - both look like 50Hz.

A 200kHz sample rate has no chance of showing a 20MHz crystal. You may get something at higher harmonics/mulitples of the sample rate if the anti-aliasing is poor.

If that image is truly from a 20MHz crystal, and not accidental hum being picked up, then it suggests something is wrong.
yep worked it out well part of it the scale down the bottom should actaully say MCS not MS it might be a tiny bug

it must be somthing harmonic or somthing of that nature for a 20mhz wave there has to be 20 cycles per Usec i'll have a better look tomorrow when i'm not tired...
 

Tom2000

Senior Member
#15
Oops! Dippy, I should have caught that. <embarrassed>

However, despite the limited frequency response in o'scope mode, that's awfully tempting to buy for just the logic analyzer function.

Tom
 
#16
Don't worry Tom, when I first saw the piccy I thought it said nS!

For 1mS (nS?) I was going to throw my Tektronix out.

(I have witten a couple of PIC and dsPIC apps for 'scope onto 128x64 GLCD and the fastest I could get the PIC to sample at was about 200ksps if I remember correctly (prob not). It could just about display a 20kHz sine wave but without fancy interpolation it looked steppy. I never got round to external ADCs. I did, however, see the clear effects of aliasing.)

Obv. logic you can run it a lot faster. No ADC obv again.

I'm sure that device will be fine for Logic and audio freq stuff, but for checking the sine wave of a crystal or ultra-sonic it'll be a no-go.

For those apps it looks reasonable value for money. An entry level PicoScope will cost a lot more than that, but does up to 20 MS/s sampling rate and 2 MHz analogue bandwidth.

Cliches: Horses-for-Courses and You-get-what-you-pay-for.
:)
 
#17
so far i'm quite happy with it it fits in perfectly with what i need
the logic part is very good as well

for the higher speed stuff i have a proper analogue osciliscope on it's way

i think the problem was probably somekind of interference i'm going to build a properly regulated power supply as i'm guessing that usb ports aren't exactly very smooth on the power front
 
#18
Have you tried connecting the probes together or scoping a battery via various resistances? If there is any nasty ripple then that will indicate something is slightly amiss. I get about 3mV noise on my scope with leads connected together.

I just scoped my USB 5V and get about 20mV noise with 50mV p-p 1kHz blips.
 

D n T

Senior Member
#20
Lookinh for a USB oh silly scope?

I wouuld like to get on that is a little more mobile than the 100 dollar dick smith one, although it does the job well. I found this on in my altronics cattle dog, have a look at :
catalogue number: Q0145
page 125 in the 2007 - 2008 catalogue, although check the net at the altronics . com site.
Its only $300.00 although I don't know if it comes with a probe
 
#21
DPG:"here the ripple i get"
- from your USB? Shorted cables?

If it's from USB it's about the same as I get.

Which makes your crystal measurement a bit worrying unless you erred with the connections?

I've just scoped a 20MHz xtal using a Tektronix. It showed about 3.5V p-p in Xtal2 and 4.5V p-p in Xal1 pin. The 'measurement' function gave 20.000 - 20.06MHz frequency result. Pretty good for a 10 year old box.

I would guess that your graph was a bit of signal getting past filter or a bit of mains hum being picked up. I'd be interested to see what it would make of a 4MHz crystal or maybe lower down the scale - say 40kHz where 'more signal' will be getting past anti-alias filtering.

Do you have a calibrated signal/function generator? I'd certainly be testing this device before trusting it.
 
#22
DNT: I went to Altronics site, pasted your code number and 'No products found'.

They seem to do a number of unknown brands of CRO, none seem to have the option of calibration so you'll have to trust the Beijing Boy's mass produced set up.

This is always my issue with instruments - you've GOT to be able to trust them. If calibration (or availability of a genuine unique calibration certificate) is NOT an option then either, A) The supplier is just a 'box shifter' or , B) the product ain't good enough to justify calibration. The third option of the product being so perfect it doesn't need it doesn't really apply to most things :)

Please don't think I'm scoffing. I'm just saying that just because it claims to be a 'scope it DOESN'T mean it's accurate. And the price is usually proportional to performance. So, before parting with your cash check it out? How? Well, buy calibrated Tektronix plus a calibrated TTi Function Generator and compare it alongside :)
 
#23
On these new-fangled DSOs, do you get the comfort of a real time trace at slow timebases eg 5 seconds per division - eg if I wanted to look at the voltage across a motor as it starts up over a period of 10 seconds then does it trace it out in real time?

...fed up with doing it on my analogue scope in a dark room with a digital camera set on 10 seconds exposure as a storage mechanism :eek:
 

Tom2000

Senior Member
#24
You folks have gotten me really thinking about these things.

I did a bunch of searching and reading, and found this Dynon EL-080.

It's a 60 MHz (40 MHz?) scope, 16-channel logic analyzer, power supply, arbitrary waveform generator, and clock generator. It runs about USD $500. It's been around a while, so it should be a mature product, with well-debugged software.

One nice touch: it comes with a good set of probes and all the cables for the logic analyzer.

The same company offers the S2X100 50 MHz dual channel DSO for about USD $250.

The EL-080 looks very tasty. Does anyone have any experience with it?

Tom
 
#25
Looks neat/cool/groovy.

No mention of any accuracy on spec sheets though - unless I missed something??

It seems to have the edge on a simillrly priced PICO product:
http://www.picotech.com/ultracompact-oscilloscopes.html
- though PICO are brave enough to quote a 100ppm time-base accuracy.

Will it match the 50ppm timbase accuracy of even the cheapest Tektronix?
http://www.tek.com/site/ps/0,,3G-19558-SPECS_EN,00.html

Though I'll freely admit the PC based ones have a lot more features..... but are they 'flash' over 'accuracy'?? I'll never know.

Anyway, if you trust it (on what basis?) and it's good enough then that, in itself, is good enough. It just depends on your priorities.

Good luck, it looks nice.
 
#27
the ripple was with the leads shorted toegther

i'm still getting the 50hz buzz even with the laptop unlugged although it does dull down quite a bit

i dare say that my usb port is probably very noisy, and what probably doesn't help is the powerboard about 1ft away
i'm probably picking all sorts of interference from all over the place

i need to pickup a shielded pair of cro leads as well
and then i need to build a properly regulated power suply for it as well

at the end of the day i did get it mostly for looking at 3.3v and 5.0v logic signals most of which will barely hit 30khz anyway,

i do have a proper osciliscope on the way that i'm going to use for looking at things like crsytals and generally anything that the usb scope can't see

being realistic though for $169Usd i think it's worth it,
 
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Tom2000

Senior Member
#28
Though I'll freely admit the PC based ones have a lot more features..... but are they 'flash' over 'accuracy'?? I'll never know.
Thanks for your wisdom, Dippy. You saved me from instantly dragging out a credit card. (Actually, I was about thiiiiiiissss close to ordering it about 12 hours ago, but thought it would be a good idea to pause, think, and research it all a bit more.)

Guess I need to to some more reading and research.

Tom
 

Tom2000

Senior Member
#29
being realistic though for $169Usd i think it's worth it,
For the logic analyzer alone, I agree with you 100 percent!

I noticed that the logic analyzer software has canned routines for analysis of SPI and I2C interfaces. That's a really nice feature that might come in very handy at 3 AM, when you can hardly keep your eyes open.

Tom
 
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#30
Dear Martin,

have a look at the DATA SHEETs for these products.
PICO as slow as 200 seconds pr div. Tek 50s per division. Elab 5s per division.
http://www.picotech.com/document/datasheets/PicoScope2200.pdf
for example.
Yep, I understand that - what I was (trying) to ask was whether you see the trace going across the screen in real time like a normal 'scope or it sits and captures the waveform over 50 seconds at 5s/div and then displays it all of a sudden. e.g if you were measuring a pot wiper that you were waggling, could you make a 'etch-a-sketch' type waveform in real time or would you have to wait 50 seconds to see the results?
 
#31
...and I too, was researching the Pico range, but their online forum is quite revealing in parts with alleged:
- quality control
- noise
- doing a mischief to your PC since they are USB powered with common ground so if you do something odd/silly with the ground connection on your probe, it ends up inside your PC (I believe some PC scopes have optical coupling which would seem a Good Idea)
- 'freezing up' and needing to be replaced

I just keep looking at the Tek TDS2014B....please persuade me not to..... ;)
 
#32
Yes, you can use a DSO as an 'etch-a-sketch' .
Literally if you connect another pot to the x-axis.
Use it to store pictures by connecting another signal to the Y (brightness)input.
Having said that though, I'm talking about the one I had at work (Gauld) which cost > £10k, so check the spec of whatever you buy first.
 
#33
I just like the old-fashioned capabilities of putting a probe on an output that's meant to always be at zero but there's a suspicion that it's sending out short pulses randomly and rarely...
...so you turn the brigthtness right up and stare at the screen waiting to see a pulse somewhere on the display.

I suppose these days you set a delayed trigger on the input and just wait for the DSO to capture it when it happens and then you can analyse it in all it's gory details by zooming in, doing maths on it with traces from other channels, downloading the picture into your PC to post here etc etc

I think I need to see one in action - would Tek lend me a demo TDS2014B for evaluation as just a one-mad-band-in-a-street? (EDIT: oops "one-mad-band-in-a-street" -> "one-man-band-in-a-street" - now there's a good name for a group!)
 
#34
Believe me, you can do all sorts of 'mischieves' when testing things with (particularly mains) power supplies and scope ground leads. It's not the unique territory of a USB scope whatever make. But it is the territory of forgetfullness, stupidity and Newbies.

I did a stupid the other day shorting grounds via mains, and was saved by the Current Limiting on the TTi supply. Nearly popped a Tektronix. I like to think it was forgetfullnes (!) 3 amps through my Tek ground, ooh!

So, if you made cockup, would you sooner blow up a £300 notebook or a £1k Tektronix??

How can you have an optically coupled ground?


Martin, of course Tektronix will give you one, just ask for one of each model to test on a permanent basis. If the lads at Tek have had a grumpy weekend then your request will give them a good laugh.

They probably read this Forum every day and see all the tips on how to scrounge a free sample.

Of course, these days, if you said you would like to do research into the effects of using a 'scope on Global Warming, then you'd get a grant. Remember to throw in all the cliches, such as 'embracing new technology' , 'celebrating the cyclic nature of the environment', 'I love cheap CFLs which only last 6 months'. And how, by moving all manufacturing to China, we can reduce our own country's CO2 output and be very smug.
 
#35
:eek:cfls that last 6 months

i've got one here in my garage i screwed it in about 11months ago turned it on and havn't turned it off since

yet i've got two in the upstairs hallway and bathroom and niether have lasted any more than 4 months

it seems the more they get turned on and off the sooner they fail,

the whole manufacturing issue is happening over here as well, and it's starting to be the case with the food industry we're growing less and less and importing more and more
 
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#36
Absolutely, and if your wall switches are getting-on a bit that will affect lifes. Some are not recommended in enclosed or pendant fittings.

All 6 of my Chinese £1.99 'Pro-Lite' have failed within 20 months, 3 within 4 months all used in open fittings indoors. One actually went up in smoke and set my alarm off.
Only 1 out of 7 of my £4.99 German made Osrams have failed in over 5 years including 2 outdoor in sealed fittings.
So, if I hadn't been so much of a tight-wad I should have bought all Osram and the delivery distance is less. But then everyone in the world is becoming a tight-wad, I want the cheapest, hence the success (and regular disposal) of cheap poor quality products.

So, why oh why, are some right-on Governmnts planning to make them mandatory?
Trendy. Darned politicians.
LEDs.... the answer.

And don't get me onto the subject of a new printer being cheaper than a set of ink cartridges.... jeez no wonder landfill is full of old printers.

:END of Sunday Rant.
 

papaof2

Senior Member
#37
landfills and other rants ;-)

But then everyone in the world is becoming a tight-wad, I want the cheapest, hence the success (and regular disposal) of cheap poor quality products.

So, why oh why, are some right-on Governmnts planning to make them mandatory?
Trendy. Darned politicians.
LEDs.... the answer.

And don't get me onto the subject of a new printer being cheaper than a set of ink cartridges.... jeez no wonder landfill is full of old printers.

:END of Sunday Rant.
I have a couple of (reletively expensive) LED bulbs for outside security lighting. At less than 2 watts draw, I consider them "exterior nightlights" (and even these are on a dusk/dawn sensor). With light output comparable to a 10 watt incandescent bulb, they provide just enough light to make the holly bushes at the corners of the house unusable for concealment - without the light pollution and power needs of standard floodlights.

Printers are today what snapshot cameras were in the early/mid 20th century - a way to sell supplies. Kodak sold entry level cameras at (or below) cost to encourage people to take more pictures, resulting in more sales of film and processing. Even Xerox tried to lock copier customers in with "Your warranty is invalid if you use non-Xerox paper or toner" - that did not survive a court challenge.

Inkjet printer manufacturers tried the same warranty wording about ink and found no greater success. People bought after market cartridges and the cheapest of us (or those who printed a lot) refilled the cartridges (although I've found a source of cartridges for my Canon printer that's so cheap I've stopped refilling). Then the manufacturers went to "smart" cartridges with embedded chips that prevented the printer from recognizing the amount of ink in a refilled cartridge, thus creating a market in "chip resetters".

CFLs are fine for some things, but be very careful of the light color when putting them in a woman's makeup area. The first time a female politician (or a politician's wife) finds herself looking bad because of the lighting, there's a good chance for exceptions to be made to the mandatory CFLs. In addition to the short life, some CFLs start up slowly - maybe a half second or more to produce *any* light output; not good when the first impulse is to flip the switch again...

What relation to PICAXE? Being cheap (and the state of Georgia being under almost total outdoor water use ban), I'm building a PICAXE controller to automate irrigation of the wife's flowers with collected rainwater. Since this is a gravity flow system (less than 3psi), standard irrigation valves don't work; thus I'm collecting pieces from industrial suppliers (DC valves instead of AC) and will use a PICAXE to monitor and control water flow (measuring in gallons delivered, not just the number of hours the water is turned on).

John
 
#38
inkjet printers.....
over here in our little eschelon of society donw here in southwest sydney, a large number of us went through an interesting process with the lexmark printers

the pricing used to be at the point where what we used to do is buy a printer with a black cartridge and the color cartridges for $49 then with the refill ink only costing me $6 from the markets

the cartridges would only survive maybe 3 refils then were cactus

so instead of getting new cartridges we just got the printer that came with the cartridges which was cheaper than the cartridges were alone

it worked to the point where we had 7 lexmark printers on the garage floor still in their boxes and plastic,

needless to say the wife kindly donated them to one of the local charities as we couldn't even sell them

kind of sad is't it?
 
#39
Blimey. And I bet you're not the only one with a pile of pinters for exactly the same reason.

Even the 'replacement' (non-orirignal) cartridge market is highly touchy. I bought non-Epson cartridges for my Epson recently. First time I've done that - due to paranoia that they'd bung up. But my R800 drinks cyan even when just printing black.
Due to legal reasons they are a slightly different geometry and don't click-fit so well but they work fine.
Did you see that HP have come to a deal with Staples in US&UK? Something along the lines of We (HP) will give you (Staples) a wedge of cash if you promise ONLY to sell HP cartridges fo HP printers.

It just amazes me (but not surprises) that with all this obsession with CO2 and recycling that something isn't done 'at source' i.e. incentivising the manufs NOT to encourage waste.

Now look, you've got me onto ink-jet cartridges...
Epson R800 review: Fantastic, best I've seen, but so heavy on the juice that it's gotta go. I think £100 per year on ink is enough don't you? (It hardly get's used). It's the printer equivalent of a feline alchoholic: drinks like a fish and always cleaning itself.

Anyway, enough, I'd just change a cartridge. Cyan out again..... but not Epson this time.
 
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