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Advice re oscilloscope choice for automotive diagnostics?

Question asked by Basil on Dec 8, 2011
Latest reply on Dec 12, 2011 by mkawasaki
I am relatively new to oscilloscopes, I wonder if someone could help me here to decide what type of bench scope I might need, please?

I have been using a Dataman USB scope ... scope.html for basic automotive diagnostic work, looking at injector and coil waveforms, reading the outputs of cam and crank sensors, both Hall effect and magnetic, watching thermistor voltage outputs, and looking at throttle position sensor outputs, etcetera. It is not an automotive specific device like, for example, some of the Picoscopes, but this has perhaps worked to my advantage, as rather than pushing on screen menu buttons to set up scaling automatically, I have had to think about what I am trying to measure and do it manually. It has helped me get a basic grasp of signal levels.

I now find carrying a laptop around and the Dataman scope, making sure the battery in the laptop doesn't go flat, being worried something's going to get knocked on the floor, blah blah, is a PITA and would also like a bench oscilloscope. Ideally I was asking about those with battery power options, but I think these will be out of my price range and I will have to continue to use a USB scope and the laptop when on the road, or inside a moving vehicle.

I now find myself realizing just how poor my grasp of scopes in general is. I need advice on whether I should be looking at analogue or digital bench scopes, what bandwidth I need to look for, and how many channels I really need. I certainly need two, but I have a Thurlby Thandar 20 MHz multiplexer ... lexer.html that might allow me view multiple injector or coil patterns on a single scope input. I have never tried it as I am told you need a scope with a degree of persistence to use it, and I don't think all USB scopes would have this? I would also ideally like a colour display scope, to make differentiating two or more traces easier, and I like the USB scope for its ability to show voltage levels and things digitally on screen. I suspect, but don't know, that these criteria will mean I need to look only at a digital scope?

The other thing I need advice on is depth of memory and real time sampling rates. I know Pico go on about how important this is for storing enough data to find an intermittent glitch.

Size and age of machine isn't a real issue now I have decided to consider a bench based instrument. My budget is $1000 max, so will be looking at used stuff. I quite like vintage stuff, so am not necessarily looking for anything on the basis of it "looking modern". I would not want something totally irreparable unless it was dirt cheap though. Can anyone give me some pointers please?

Thanks for reading.