USB oscilloscopes – are they any good?

[Enough!Participant @enough]

Posted by Robin Graham on 13/08/2017 21:07:14:

no longer have a machine with a parallel port

Don't know what it's like where you are, but around here you can pick up an old pc for next to nothing. There are stores that specialise in off-lease hardware and the older stuff is just taking up room to them. If you look at it for long enough, they throw it at you.

Or there's the Sally-Anne etc.

[V8EngParticipant @v8eng]

If you still want to experiment using Duncan's offer, would a USB to Parallel (printer) adapter work? i've seen them in the Maplin catalogue.

(Other suppliers as well no doubt).

 

Edited By V8Eng on 14/08/2017 00:01:11

[Geoff TheasbyParticipant @geofftheasby]

Stewart of Reading have been in business for years and sell good, reasonably priced, used test equipment. (No relation)

Geoff

[SillyOldDufferModerator @sillyoldduffer]

Posted by Robin Graham on 13/08/2017 21:07:14:

I might even bid on eBay for an analogue (any scope is better than none!) but these are often offered 'as seen' by people who I suppose dismantle labs and have little idea of what they've got – it lights up. Might be worth a punt though.

…

Personally I'd avoid buying an 'as seen' oscilloscope. My experience of trying to fix them has been disappointing, even armed with a Manual and Circuit Diagram. The problem seems to be that some oscilloscope innards are both complex and delicately balanced in terms of component values. As the instrument ages more and more parts drift out of spec until the thing stops working for non-obvious reasons. (No smoke.) Diagnosis is difficult and a fix may require multiple parts to be changed. Also, the best way to debug an oscilloscope with another oscilloscope!

Of course, my advice can be safely ignored if you have the aptitude and wherewithal to do this kind of work.

Dave

Edited By SillyOldDuffer on 14/08/2017 09:47:52

[Swarf, Mostly!Participant @swarfmostly]

Posted by Geoff Theasby on 12/08/2017 14:47:05:

SNIP

Furthermore, I recently acquired an AVO 8, one of my life's ambitions. The difficulty of obtaining the right battery is of no consequence, since any cheap (£5) digital multimeter will be more accurate for testing resistors than the AVO. Surely most people have more than just the one multimeter?

Geoff

Geoff,

Of course you're quite right as far as resistance measurement is concerned. I have a Fluke 8020A which has done very well over the years (once I got Fluke to replace the poisoned LCD display). It still does very well, I keep it for Sundays! I recently replaced its PP9 battery with a long-life lithium based battery of identical envelope. I also have a little hand-cranked Megger whose Ohms range comes in useful for low resistance measurements.

For an 'every day' meter I also have a sub £5 digital multi-meter that is powered from a sub-AAA 12 volt battery – you don't want to leave those switched on by mistake, those batteries are almost as rare as the AVO 8 15 volt battery. Using that instrument's 200 Ohms range seems to flatten the battery.

Regarding the AVO 8, I just like the idea of maintaining it in the condition in which it left the Avo factory. When I bought it in the 1970s for £37 10s from Watts Radio in the Apple Market, Kingston, they were the pinnacle of desire for radio and electronics hobbyists. A few industry colleagues claimed to be able to get me an AVO 8 much more cheaply but theirs wouldn't have come with a document showing indisputable legal ownership!!! I subsequently found both a leather case and even a spare movement in the Lisle Street emporia.

Off topic but it might help someone: be careful when buying a 'tong' multimeter – the cheaper ones only measure AC current via the tong, not DC current!

Best regards,

Swarf, Mostly!

[Neil WyattModerator @neilwyatt]

Oh dear, I have quite a collection, at least five or six analogue ones, including a huge Eagle, (my Dad had two used everyday AVO8 kept for Sundays) and a Taylor Transistor Tester, I converted to a multimeter. I only use the cheap digital ones now, cheaper, more accurate and less stress when using the high current ranges!

Neil

[Neil WyattModerator @neilwyatt]

On an analogue scope the frequency is much 'softer' tan on a DSO as it's really the frequency where the wave shape starts to distort (e.g. digital signals start to look like sine waves…) and you can often get usable, if distorted, traces up to twice the frequency or more depending on what you are trying to do.

[Geoff TheasbyParticipant @geofftheasby]

Yes Dave. If you have the experience and the skill. In a start-up I was involved in, we equipped the Chief Engineer with used professional gear from Iwatsu, Kokusai, Anritsu etc., plus Marconi, H-P and Rohde & Schwarz, that's where I learned to use a Spectrum Analyser. Both the MD and Chief were brilliant, then there was me, who did everything else! Great times.

Geoff

[MuzzerParticipant @muzzer]

+1 for the likes of Siglent. You can get a (brand new) 2 channel 100MHz DSO for under £300 delivered. They are pretty much what you'd get from Tektronix for 2-3 times the cost. I know, having used both.

When you see the equivalent products from the likes of Pico, you have to ask yourself why bother. They cost more and you can't use them without a PC.

Murray

[Stuart BridgerParticipant @stuartbridger82290]

This topic has rekindled some interest. It's a long time since I used scope in anger. Only ever used analogue scopes, but a spell in a repair and calibration shop gave me a lot of experience on a variety of vendors. Having browsed the RS website. I see that they have a huge range. I am amazed that you can get a very well specified 100MHz digital scope for around £350 with their own brand. RS have never been the cheapest, so I guess you could get cheaper elsewhere. Like others have said, I see little point in getting a USB model, when you can get a standalone unit for these prices.

[Robin GrahamParticipant @robingraham42208]

Thanks for further replies – I think the verdict is coming down firmly in favour of a standalone unit. The Siglent on Amazon which Murray gave a link to looks good, though weirdly (unless I've missed it) they don't give a figure for the ADC resolution – a fairly fundamental spec I'd have thought. Presumably that means it's 8 bit.

This has turned into one of those shopping expeditions where you start with a sort of provisional budget of £n, then think 'but £(n+n/2) would get me so much more', and that becomes the new baseline. Then £2n, and so on, and before you know where you are nothing less than £10n will do.

Thanks for your warning about buying 2nd hand unseen Dave. It reminded me of the time I took a failing scope to the electronics shop at work and was met with a dejected 'well I suppose we can have a look, but it might take some time, can't you buy a new one?'. I think I understand why they said that now. I certainly don't have scope repairing skills myself.

Today the local water board (subcontractors actually) dug a trench outside my house and managed to puncture the water main resulting in the release of possibly thousands of gallons of water – some of which has found its way into my subterranean workshop. And completely dissolved my 4-channel 5GHz LeCroy it seems! A claim will have to be made . So electronics on the back-burner for the mo while I get to the swabbing out. All part of the rich tapestry of life I suppose.

Robin

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