Thinking about an Oscilloscope and Signal Generator

[Ted]

As I'm moving along with some of my projects, specifically the Caterpillar diesel swap into the Land Rover and then also some other things that I may be doing on the RV, I'm thinking that it would be useful to have some sort of oscilloscope at the very least, and likely also a signal generator, to help figure out what the system needs and make sure things are working correctly.

When I was in school, oscilloscopes were all expensive, and not something practical to buy as a hobbyist. I also was a mechanical engineer, and have mostly avoided electrical stuff because I can't fix it with a hammer. Now I suppose things have changed, especially with the general shift towards digital interfaces over analog ad the continued forward movement of technology. There's lots of <$50 single channel O-scopes on eBay and other places. I have no idea if they're any good, but my first thought is that those would probably meet my needs just fine.

Similarly, a basic signal generator that lets me do varying types of waves with a PWM signal would be good to have, and it seems those are also easily attainable in the <$50 range.

Am I wasting my money with stuff like that? Are there better options? Should I just stick to using a hammer?

 

[Half Fast]

You’re wasting money. If you only need low frequencies, just go with an app on your laptop.

Example: http://www.zen22142.zen.co.uk/Prac/winscope.htm

A little googling will find many oscilloscope programs that use your existing sound card for I/O.

 

[flyingbrit]

A fundamental problem with a sound card is that it will not pass DC. DC coupling is essential for an automotive use 'scope.

 

[flyingbrit]

For a little more money you could get two channels which is far more versatile. For example:

https://www.amazon.com/Hantek-Oscil...cphy=9017003&hvtargid=pla-1127217624411&psc=1

 

[Ted]

I think I would prefer a dedicated unit to something that goes through the PC. I agree two channels would be nice to have vs. 1, especially as input/output is something to check of certain items. Plus, my PCs really are mostly junk (or work) and I don't want to have to carry one out to the shop.

 

[Half Fast]

A fundamental problem with a sound card is that it will not pass DC. DC coupling is essential for an automotive use 'scope.

Ah, good point. I didn’t realize Ted would need DC coupling.

 

[chartbundle]

I have a Rigol DSO I'm happy with, they're in the $350 range now. There are also decent multimeter styles for around $100-150. I don't think I'd go lower than that unless you really just need a graphing multimeter, and in my mind 2 channel is a must. There are a few with on-board CAN decoding too, which would be handy for 'modern' electrical systems I'd think. Some even seem to have their own on-board signal generator, but dedicated devices seem to be around $100 now.

 

[kontiki]

Only you know how much of this sort of work you will do. Most everything is digitally done now a days. The reality is once you capture the signal digitally (the A/D), you can post process on a lot of platforms. That's where it becomes an O scope, or spectrum analyzer or whatever. I'd identify the highest frequency of interest and make sure the sampling rate is around 10 times that.

 

[kshaw]

Have you looked into the NanoVNA? Lots of capability for a lower cost.

 

[Albany Tom]

When I was in school, the joke was that the EE's designed weapons, and the civil engineers designed targets. I had a new-then Heathkit 35 MHz scope because I was more than a bit of a geek. The new inexpensive mixed mode scopes are much less expensive, and much more capable.

Rigol and Siglent both make stand-alone scopes that will decode some common serial protocols. But 'common' depends on the application. I2C and SPI are common microcontroller protocols, but I'm not sure if they're widely used in vehicles. Last I knew, CAN was pretty common. I believe some Siglents can decode CAN, but not sure about Rigol. You might want to take a look at the Siglent SDS1202X-E. That's more or less entry level these days. Only 2 channels, but 200 MHz and it's supposed to decode CAN and LIN as well as I2C and SPI. I don't think you'd be happy with a stand-alone scope less than that. The VNA mentioned above, for radio work, is great. But my take on $50 stand-alone scopes and logic analyzers is that they're toys. (I could be wrong. I'm kinda spoiled as always having had a scope with actual knobs.)

One other thing to consider, though, is that dealing with data on a scope can be kinda miserable. At the low end, they do not necessarily have any way to get that data out to manipulate it, or even decode it if it's wider than the screen. A PC based USB logic analyzer may be a much better choice. Not sure what is in that market for decoding vehicle data, though.

All of the above is done without any knowledge of current diagnostic equipment for vehicles. It's very possible there are low end analyzers, beyond just odb2 scanners, that will let you play with the data.