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Automotive oscilloscope diagnostics



dann2707

ClioSport Club Member
Hi all and morning Porl,

So basically I've got myself a scope kit (picotech 2204a) which is a two channel kit.

I've spent the past 2 weeks watching some YouTube videos and their capability in terms of individual tests you can do in the automotive industry with them such as:

Relative compression tests
Pulse testing using a piezo sensor
Alternator, battery and starter tests
Injector testing
s**t loads more

I got it to play around with really and have no immediate problematic vehicles to work with but I want to make sure if anything does start to fail I'm prepared and know how to use it for what I'm trying to diagnose.

Anyone used this particular kit using the picoscope software?

Just want to get an idea of who's used them before and other tests they can be used for.
 

Touring_Rob

ClioSport Club Member
Hi all and morning Porl,

So basically I've got myself a scope kit (picotech 2204a) which is a two channel kit.

I've spent the past 2 weeks watching some YouTube videos and their capability in terms of individual tests you can do in the automotive industry with them such as:

Relative compression tests
Pulse testing using a piezo sensor
Alternator, battery and starter tests
Injector testing
s**t loads more

I got it to play around with really and have no immediate problematic vehicles to work with but I want to make sure if anything does start to fail I'm prepared and know how to use it for what I'm trying to diagnose.

Anyone used this particular kit using the picoscope software?

Just want to get an idea of who's used them before and other tests they can be used for.
Not picoscope but I've used proper oscilloscopes to diagnose car issues many times, oddly never on anything that doesn't have an aftermarket ecu though - not sure why. perhaps accessibility of ecu connector and easy use of test modes that most aftermarket units have.

How does the compression test work? Did yours come with a sensor for that? sounds handy for keeping a record.
 

NorthloopCup

ClioSport Moderator
How does the compression test work? Did yours come with a sensor for that? sounds handy for keeping a record.

To do the compression tests at work using the imib (bmw oscilloscope) it works off an amp clamp to measure the current draw. Very clever how it works, and when I was shown at the bmw training centre the imib vs a proper compression tester, the results were remarkably close.

Very good for being able to see wave patterns on sensors as well, which is essential for certain diag work.
 

Touring_Rob

ClioSport Club Member
To do the compression tests at work using the imib (bmw oscilloscope) it works off an amp clamp to measure the current draw. Very clever how it works, and when I was shown at the bmw training centre the imib vs a proper compression tester, the results were remarkably close.

Very good for being able to see wave patterns on sensors as well, which is essential for certain diag work.
Thats pretty smart - I take it you have to select which engine the car has before it will give you a result? I'd guess they know what the current draw for that particular engine should be so by measuring the current and comparing it to their gold standard result they have see a %decrease etc.
 

NorthloopCup

ClioSport Moderator
Thats pretty smart - I take it you have to select which engine the car has before it will give you a result? I'd guess they know what the current draw for that particular engine should be so by measuring the current and comparing it to their gold standard result they have see a %decrease etc.
Yeah but it’s reasonably basic in terms of choice, so 6 pot, 4 pot, 3 pot, petrol or diesel.
But we actually have a test module now where they turn off the injectors and measure the speed that the engine slows down on each individual cylinder. That’s also very, very accurate for the readings you get.
 

Touring_Rob

ClioSport Club Member
Well, it would be quite easy to make a device which tells you if you have one (or more) low compression cylinders without actually giving you a cylinder pressure figure.

For me the impressive bit is that they can give a figure with such basic input data and get it ball park accurate. Measuring crank speed is nice way to do it too and potentially easier to get an accurate figure for pressure.

In the Scorpio cosworth, ford managed (In the 90s) to run the engine full seqiencial, with knock control from the crank sensor alone by measuring acceleration accurately enough. Was pretty smart at the time!
 

dann2707

ClioSport Club Member
Well, it would be quite easy to make a device which tells you if you have one (or more) low compression cylinders without actually giving you a cylinder pressure figure.

For me the impressive bit is that they can give a figure with such basic input data and get it ball park accurate. Measuring crank speed is nice way to do it too and potentially easier to get an accurate figure for pressure.

In the Scorpio cosworth, ford managed (In the 90s) to run the engine full seqiencial, with knock control from the crank sensor alone by measuring acceleration accurately enough. Was pretty smart at the time!
On the vids I've been watching you can select compression test on the software and ensure you're using another channel for a reference cylinder so basically a coil plug activation. That cylinder is then your reference as its almost always nearly at tdc. It then overlaps the cylinder pulses as you then enter the firing order of the car.

Picoauto have loads of case studies where the scopes applied. I read this one today and it goes into lots of detail.

Probably going to have a play with my mrs car as its very basic and easy to get access to everything.


The compression tester is a nice way to check quickly if everything is good. Great for buying a car as you're not then removing all the spark plugs to do a compression test haha.
 


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