Which Oscilloscope?

[rurwin]

What switched me of Velleman was when I bought one of their kits. It came with no schematic, no source-code, and the PIC processor had its security fuse blown so you couldn't even see the code it was running. Fortunately I intended to reprogram it anyway and I had a spare processor, but I had to trace the tracks on the PCB to find out how to do it.What is the purpose of a kit for a one character scrolling text display if it isn't educational? And how can you learn anything if you can't see the circuit or the code?

does sound pants. There seem to be other manufacturers making 'pocket oscilloscopes' :



I wonder if any are any good?

does sound pants. There seem to be other manufacturers making 'pocket oscilloscopes' :



I wonder if any are any good?

Without a proper probe nothing is going to be much cop at anything far higher than audio frequencies. I can't help thinking that the best "bang for buck" (I hate that phrase and can't believe that I just typed it!) would be gained by looking out for proper, full-sized test equipment being sold by e.g. a hobbyist downsizing / upgrading, etc. At least the internet is always there to research specific pieces of kit, check out user reviews and whatnot before parting with folding money.

unfortunately I cant recommend a velleman personal scope. I have one and it has been nothing but trouble. It will only work on alkaline batteries but eats them very quickly ! cant get it to work with NiCd or NiMh at all because it always crashes within minutes ! it wont boot up when powered by a +9V supply either ! not good at all

Is it not just that the alternative PSUs you've been trying are unable to deliver enough current?
Perhaps you need a more beefy power supply?

No I have been using a high quality regulated 5A bench supply...

Can anyone comment about the usefulness of these http://proto-pic.co.uk/oscilloscope-kit-digital-diy/ for general hobbiest use.

Thanks

5 million samples per second and analogue 1Mhz sounds good but I don't really know much either

What scope you use depends on

• How much money to spare
• What you want to look at
• What other functions you may need
• How long you think you will keep it

I have had old analogue scopes that were 30 years old function well and for a long time (last was a Tek 475). Digital scopes are nice and have lots of features I currently use daily a Tek MSO2024 (well out of most peoples budgets), but BEWARE There are many articles about on the net about choosing scopes but here are a few things to bear in mind

• Sampling speed must be higher than analogue bandwidth good factor 5X or more
• Beware of USB scopes unless you want to buy a new one when you buy a new PC and the software woint work on the new PC
• Check what voltages it will take as inputs
• how many trigger methods
• Sample depth that can be stored
• Can you transfer waverforms to PC direct or via USB pen drive

The biggest killer of most cheap scopes is a method known variously as

• Repetitive Sampling
• ETS (Effective Time Sampling)
• Iterative Sampling
• Other marketing names

Basically these are great for looking at sine waves, but useless at looking at things like high speed SPI or I2C transactions. I have seen some of these scopes be unable to display 3 bits of an I2C transaction at 400Kz on a 200MHz bandwidth scope. This is because below a certain timebase setting, what you see on the screen is made up from many sampling sweeps, hence the names like repetitive sampling.

This is often seen even on Rigol (also sold as cheap end of HP/Agilent) and similar scopes.

I personally have used Picoscope, and the scopes themselves are fine (a friend has done designs of their analog front ends on some of thei newer high end scopes), the software often lets them down, and in one case one customer had them in use for production built into test suites, and when they expanded the test suite 12 months later had to replace the old scopes with new scopes at £900 each as the models had changed. Then the software interface to control them in a test suite was totally different as well.

[rurwin]

Digital scopes these days have more and more features and they are getting harder and harder to ignore, but it's still the case that a scope of any type only tells the truth within certain parameters. Roughly speaking, that's a smoothly changing and repetitive signal at a frequency significantly below the bandwidth of the scope. Outside those parameters, an analogue scope will tell you the truth, so far as it is possible, albeit it may need some interpretation. However a digital scope will tell lies; it will delete entire features of the waveform, such as fast spikes and it will tidy up square waves and remove ringing. A cheap scope may even change the frequency of a signal or introduce a false signal due to mixing with the sampling frequency.

The answer is always to get to know the limitations and behaviour of your equipment. That's probably easier with analogue scopes where it is all about bandwidth. Digital scopes of course are easier to use and read... if you use them correctly.

Yes, the DPScope works well. Aimed at the hobbist market , but then thats what I am. Probably more info on the Pixaxe foum. The software is for Windows (sorry about that folks!)

I've been agonising for a few weeks about whether to buy a used "great big box" or a brand new "small usb box". In the end the size won out. That and the fact that it's easier to do a screen-capture on something running on a computer. I was also a bit concerned about a great big CRO getting damaged in transit.

I chose the DPScope as it gets good write-ups. I doubt it'll be here before Christmas though. I'll let you know how I get on with it.

Yes, the DPScope works well. Aimed at the hobbist market , but then thats what I am. Probably more info on the Pixaxe foum. The software is for Windows (sorry about that folks!)

I've been agonising for a few weeks about whether to buy a used "great big box" or a brand new "small usb box". In the end the size won out. That and the fact that it's easier to do a screen-capture on something running on a computer. I was also a bit concerned about a great big CRO getting damaged in transit.

I chose the DPScope as it gets good write-ups. I doubt it'll be here before Christmas though. I'll let you know how I get on with it.

Well it is rarer these days to even get NEW big boxes with CRO, they have LCDs. It is also rare they are damaged in transit (unless secondhand) as they packed similar to monitors/TVs/Laptops.

Anyway for anybody looking for lowend USB scopes this is worth a look, 5MHz bandwith 100Msps 14bit dual scope, logic analyser, pattern generator, and more. May consider one soemtime myself for pattern generation and the like. Already have bench scope/logic analyser

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1018&Prod=ANALOG-DISCOVERY&CFID=82299&CFTOKEN=83961379

In UK http://uk.farnell.com/digilent/410-244/analog-discovery-design-kit/dp/2143587

Anyway for anybody looking for lowend USB scopes this is worth a look, 5MHz bandwith 100Msps 14bit dual scope, logic analyser, pattern generator, and more. May consider one soemtime myself for pattern generation and the like. Already have bench scope/logic analyser

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1018&Prod=ANALOG-DISCOVERY&CFID=82299&CFTOKEN=83961379

In UK http://uk.farnell.com/digilent/410-244/analog-discovery-design-kit/dp/2143587

Looks nice. Bit more than I paid, but it does seem to have more bandwidth. A new big box wasn't really in the budget unfortunately. I doubt the scope will be used a huge amount. If it turns out that it's justifiable and needed, a big box will be bought.

Well I got my DPScope yesterday - bit of a delay due to Christmas post. Had a quick play and it seems to work quite well. Here's a screen grab of a sinewave output from the ADC on the Gertboard. (ADC driven by a Python script I wrote. It can only manage about 2 Hertz, but it works.)



Still playing, but early indications are that I like the scope and it's very portable

alexeames, I got my DPScope last week. I like very much the scope and it seems to work pretty well. I was able to display a 200 hz sine wave sent out from the sound card on my laptop. I used the DPScope software installed on the laptop (windows).
I would like to drive the DPScope from the Raspi and to display signals directly on it.
Are you able to run the DPScope software on the Raspi?
or the python script you referred is to drive the digital2analog conversion (maybe via pwm)?