Oscilloscopes

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addo
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Oscilloscopes

Post by addo »

Since we're awash with signal techies here (well, one shy of last year with the loss of our man in France), it seemed a good place to ask about used 'scopes.

Purely for looking at either stuff on the car, or consumer goods, what kind of descriptive advice can people offer? I'm thinking dual trace, but does it need to have a range higher than 20 Mhz?

Also I am tending to think a standalone CRO is the better choice; laptop interfaces aren't that cheap and it's a lot of mucking about. Digital storage types seem dear.

Fleabay offer a decent range; you'd get a 100MHz Philips/Fluke for $500 or less, but then again I can get a new warranted 20MHz Chinese unit for under $400.

What aspects of age-related degradation are to be expected on a used item? What are the "Chinoiserie" like in quality?

Anything else I've overlooked?

(And yes, Part II of the scheming would be a signal generator with amp to test out stuff like electrovalves...)

Thanks, Adam.
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Post by xantia_v6 »

For just about any automotive use, you really need digital storage, as waveforms are either slow or non-repetitive.

A PC adapter is probably the best value these days. Don't get anything too expensive, as it is easy to accidentally fry the front-end with an errant pulse from the ignition system.
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Post by addo »

Cheapest PC adapter in a local store is $300, and I then have the potential inconvenience of the laptop, its cabling and the scope interface - rather like the Fauxia arrangement.

Point taken about transients, though.

I've got time to think it all over; only took me eight months to get a Lexia clone sorted...
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Post by dnsey »

I guess it depends what sort of non-automotive uses you envision.

You can't go far wrong with a good second-hand Tektronix scope, but that might be overkill.

For automotive-only purposes, you might pick up a slightly outdated dedicated analyser cheaply. I had an old Crypton one for years, which I bought for virtually nothing, and was excellent for checking ignition faults etc.

There's plenty of free software which will run on any old PC, so you coud dedicate an ancient scrap laptop to the job, and a cheap USB soundcard will do as an interface for engine measurements. A couple of turns of insulated wire round an HT lead will pick up the ignition pulses fine, but I'd add a high value resistor in series, and perhaps a parallel zener diode to avoid any stray volts killing the soundcard.
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