Oscilloscope specs

[EagleMark]

I've been looking at osiliscopes, just for troubleshooting EFI system conversions I do. Wondering what specs to look for? Don't need anything fancy just don't want to be checking a wire say near a spark plug wire and burn it up! :doh2:

I've found one that is powered by USB and is very small, pocket size whoch would be handy and portable. It also has a probe to pinpoint the area in question. Last time I played with one was high school a looooong time ago and until now have never seen one other than very large benchtop type...

[Ira]

I like my Fluke 98 for working on cars. A USB scope would tend to mean it connects to a computer unless it's the $79 one on eBay where it uses USB for programming and memory. It looks really cool but I'd wonder about it's ability to stand large surges. or even gentle drops. What do you think you need a scope for?

Ira

[EagleMark]

Yeah the one I was looking at was a cheapy on eBay. But I thought the usb was for power but your probably right it may be for programming or downloading... since my laptop is usually used around the car it would be fine to be needed by computer...

[Ira]

I've got a:

http://www.easysync-ltd.com/product/520/ds1m12.html

Which I've been very happy with. It's not perfect, but when it's not critical or not really fast stuff, it's a lot easier than pulling out the Tek scope. Never tried to use it on a car though. I'm sure it would work, but accidentally connecting to a plug might take out the scope and the laptop. Here's another place you might look:

http://www.saelig.com/category/PSPC.htm

Ira

[EagleMark]

I've got a:

http://www.easysync-ltd.com/product/520/ds1m12.html

IraThat looks pretty handy and has lots of other options like datlog signal generater and price isn't bad either.

I'm thinking even a cheap entry level osilliscope would handle any voltages from ECM, PCM etc... but I'm sure if you probed a spark plug wire you would fry any of them. But if you were looking for electrical noise in a ECM wire you should be able to find a spike related to a nearby spark plug wire...

[joecar]

Voltage on solenoids/injectors ranges to hundreds of volts, you need an in-line attenuator (10:1 or 20:1).

There are capacitive and inductive probes for probing ignition secondary voltages, the capacitive probes give a truer proportional voltage signal.

[EagleMark]

Hundreds of volts from an injector? How's that?

I'm not intersted in checking spark plug wires or coil wires, just EFI wiring to ECM and sensors...

[joecar]

The inductive kickback voltage from an inductive component can reach several hundred volts.

For example, when an injector is turned off (current flow is interrupted), the kickback reaches about 100V or more for about 0.2 milliseconds.

Without an attenuator the voltage exceeds the oscilloscope's input rating (can damage the A-to-D converter).

[joecar]

Look at the green waveform in the attached pic...

While injector is on voltage is zero, and when injector turns off voltage kicks up to 120V before returning to 13V.