Exploring the Picoscope as a diagnostic tool - relative compression testing

This is a high def version of a video I posted a few weeks ago. When I uploaded that video I used a compression algorithm that wasn't quite right, and this version should be easier to watch. Thank you to Curiosity and others for noticing. Other videos of labscope diagnostics are in the works and should be ready in a few weeks.

This video is the first of a video set describing the power of an automotive labscope (in this case a Picoscope) as a diagnostic tool. This first video goes into an introduction, followed by a practical description of how to perform a relative compression test using starter motor current draw to estimate cylinder compression. The theory behind the test, the limitations, and why it works are described in some detail.

For part 2, of this series, discussing secondary ignition waveforms, go here

This video is an amateur effort, published in good faith but with no guarantees as to accuracy or safety. DIY auto repair can be inherently dangerous, so consider those risks before deciding to try and repair your vehicle. Any misadventure you encounter if you decide to repair your vehicle is your responsibility.

Four stroke engine gif recorded with permission from Wikimedia commons, published by Zephyris under CC3.0 license.

Music “The Engagement” by Silent Partner, used with permission under Youtube audio list.

[sapperjohn]

hats off for not becoming just another old timer (no offense) who says "bah! i hate all the electronics in cars today" its relevant, and you adapted! kudos

[elcheapo]

The Pico is an invaluable tool, and its price reflects that. All of your videos are educational and excellent. You have a way of explaining things that anyone can follow. Looking forward to the next video. Thank you for sharing!

[howacarworks]

You are a natural teacher. Your explanations are fantastic, and very clear. One of the best videos on YouTube that deserves 100x these views!

[TheDisgruntledMechanic]

Thank you! please continue to make these Lab Scope videos!

[johneric]

Excellent work, good communication skills. Way to always return back to the basics, especially for hobbyists like myself. Much appreciated. [ I heard you mention Eric O towards the end of your video. I watch that guy's YouTube channel sometimes too. I'm making an assumption here that we're both talking about the same guy.

[gordonfreeman]

Lab scopes are great tools that will be even more relevant as cars become more advanced. But they are expensive! Anyway great video.

[stuzman]

Hey Dave! I never noticed anything out of the ordinary with the original video, but this one looks good to me from what I can tell. And you probably know this, but you can set ruler cursors inside the software between your ignition peaks. Looking forward to your secondary ignition waveform

[IntradeMotors]

I use the other Pico compression software gives green bar and % of relative compression. you have to sometimes go right to starter with ampclamp to get propper non fail reading.

[jnarez]

Great video please do some more using the pico, do a cylinder pressure transducer

[rwrobs]

Hi Dave !!...great video. I just bought myself the 2 channel 4000 series Picoscope a few weeks ago and have been using my "drive only in sunny weather" 2001 Corvette as my "guinea pig" for testing...I'm up to doing the relative compression test using my Pico 2000 Amp clamp (same as yours) and a "sync probe" I purchased from AES Wave. for whatever reason the Amp clamp was unresponsive...do you think a bad clamp ??...now if I set my scales up on the high amp clamp to a low scale would I be able to check say my fuel pump...I have used my low amp clamp to check my fuel pump and it worked great...just want to check to make sure it's not defective...I used the compression test in the Pico's diagnostic program the other evening and that worked fine...just connect to the battery terminals and crank.. Thanks !! p.s. Using the sync probe what probe do you tell the Pico you are using ???...  I don't see any clamp named "inductive" clamp in the drop down menu...I guess you use either secondary positive or inverted ??

[Ilikeryche]

I don't understand what you did with the ruler. What did you measure when making those marks with the ruler at an angle? Good Video.

[theoxygen]

Thanks for making yourself available I'm kind enough to share your knowledge, What scan tool in your opinion would be good for a hybrid vehicle? I am not a mechanic nor do I work in that field, I know that the high-dollar ones will do the job in most cases but I can't afford that so I I'm just trying to find me one that will work and give more than just a few coats here and there

[anurag]

Is it possible to do these kind of diagonistics with picoscope 2000 series of oscilloscopes?

[eriginez]

Very nice vidio...im new to pico can i remove waveforms from files..thanks in advance

[davidpaterson]

A couple of points. You said in your video – “Exploring the PicoScope as a diagnostic tool - relative compression testing” (time stamp 4.40) - that an internet connection was required to access the help files which are found in the drop down sub-menus under the 'Automotive' menu. You did add a written comment to the screen, and you are right, you don't need an internet connection for these files: they are in the software! There are just over 150 of these generic files in the software.

Maybe you initially confused this feature with the 'Waveform Library' accessible from the 'File Menu'? You DO need an internet connection to access the 'Waveform Library' - as well as a user name. You need to sign up for the free forum access, and then use that same user name to access the 'Waveform Library', which is itself only available when connected to the instrument, and to the internet!

It’s worth noting that the 'Waveform Library' currently has over 3600 vehicle-specific examples in it. This data base can be searched by make, model, VIN, component, fuel type, etc. Further, many people don't appreciate the true value of this resource. Once you find a file which corresponds to the vehicle or component you wish to analyse, you can use this file as your test file, and it will appear 'ready-to-go' with the same settings, thereby removing the need to make any adjustments to your own settings. Just select the file, hook up to the car and you're ready to go!

New users - especially those who consider the tool to be expensive - may not know that apart from this powerful FREE resource, which enables Free file sharing and the instant use of known good waveforms from a worldwide community of experienced PicoScope users, they also get FREE software updates for the life of the tool :)

PicoScope comes with 2 software programs - PicoScope 6 and PicoDiagnostics - both of which can be downloaded free, and used in demonstration mode - without buying a PicoScope. Users can see for themselves the features, including all the comprehensive help files which show both generic vehicle information, as well as a massive indexed manual and a tutorial on using the PicoScope software.

PicoScope has been designed to get new users started with the oscilloscope, which is one reason why it has pre-set menus, though these can be turned off, allowing the more experienced user to use the plethora of other features. This makes PicoScope so versatile and in my mind the best tool in the world for learning about the operation and diagnosis of any vehicle system.

Those who use price or 'it's too complicated' as excuses not to move forward with the changes in technology are really shooting themselves in the foot! Relying uniquely on the 'trusted' scan tool and its limitations is a big mistake!

Perhaps an explanation of the differences between the scan tool and the oscilloscope and a broader understanding of how and what they 'see' would make an interesting video, and encourage more people to make the transition to ‘proof testing’ with PicoScope, as opposed to trailing along oblivious to what is actually happening during a particular event, just because the scan tool has indicated a 'problem' - or because it hasn't indicated one, and the vehicle ECM is merrily adding fuel to compensate for a problem which isn't there, or isn't the cause of the problem!?

PicoScope gives us that vital information to make sound judgements about the state of operation of almost any component, circuit or vehicle system. Understanding this is key to getting away from the traditional methods which we used to employ, and to getting to grips with finding the origin of faults and to fixing them first time around!

Learning should be a continuous and fun part of our everyday work. PicoScope has certainly played an important part in keeping me interested and faintly informed, even though I no longer work on vehicles.

In the hope that this helps a few people ;)

[PackardBelltoll]

i wish you could have showed me how u connected it . I would have gave you a 5 star.