Motor Age How2 #11 - Performing Relative Compression Without An Amp Clamp
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- Опубликовано: 14 мар 2017
- Don't have a high amp clamp for your scope? No problem - you can still perform a relative compression test using this method. Pete explores the possibilities in this edition of How2.
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Short and sweet. Tools for our tool box. Thanks Pete for all your help.👍
This is great info Pete, this would be very helpful when checking a car out off the shop, I have been there with no amp clamp! Thx for sharing this.
Fantastic video, Pete. I’ve learned a lot from you and the channel. Thank you!
Great info and explanation once again,Thanks Pete
I use a low amp clamp on the 60 amp scale and set up as a probe on a 2 volt scale all the time to do relative compression test.
Great job Pete! I look forward to your videos and you never fail to deliver.
Thanks Joe. Glad you find them useful.
Great explanation
AC Coupled ! Nice ! That is ingenious !
Great teaching skills, thanks for sharing what only study and experience can provide. Greatly appreciate the lessons!!!!!!!
I found out if u have a new starter helps too u will get a great pattern I use low amp clamp on my 98. town and country and got the best pattern on my modus ultra
Thanks for this great video. I,ve just bought a scope last year and other test equipment and wasnt looking forward to spending more on an amp clamp at this moment.
For the longest time i used a low amp clamp set 2 volts at 2 seconds 60 amp ac coupled. The cables that are too big i would install a cable that i made 1 foot long and put it inline. Then i broke down and bought a high amp clamp. Scanner danner teaches the low amp clamp method. Great video i never knew about the low voltage method. One more tool for the tool box.
Good Evening Pete Meier motor age Take care and have a great day Pete Meier
Great tutorial thank you 👍
From Nick Ayivor from London England UK 🇬🇧
Low amp clamp .. yes set to 60 amps an use your voltage setting on a 2 voltage scale that will read 200 amps will work
That's awesome
Hate to say it but I have used this method for quite sometime, A change in currant results in an opposite change in voltage, As long as you have a scope that is fast enough to catch it. there are other test that can be performed using this method I will let you discuss these in future videos. Great information Pete I appreciate time and effort that you put into your videos on behalf of all of the professional technicians "Thank You!"
Thanks for taking the time to comment. I'm hoping that techs like yourself will share their experiences and techniques here so we can all learn from one another.
great information thanks for the great videos you have done . you have enough information on your scope to work out the engine speed on crank this is very importing information that some modern engines will not start if the crank speed is not right more then 200 RPM . may be you should do a update and show us out to work it out it very easy . but I let you show us how to work it out . just only last week I was asked to diagnose a car that was hard to start with the ECU light on with a crank angle sensor code this car had already had two new crank sensor but was still very hard start so I did the same test your doing in your great videos and work out its was only cranking at 140 rpm with a new battery and no voltage drop ( will there always some but it was ok ) to the started cables or the ground but with test I could see the starter motor had almost 500 amp and was very noisy that was interfering with the inductive crank sensor ! so this 5 min test I found out this car just needed a starter motor and the crank sensor was ok . so working out the speed of the engine with this test is very important
Excellent video. Minor point - the first still photo of the BOB shows the meter leads reversed just as in the second still photo of the BOB where you point out that the leads are reversed.
Damned if it isn't! Good catch - no matter how many times I go over the edits, there is always the possibility of mistakes. Thanks for bringing that to my attention.
Your students are paying attention.
lol! Good to know...
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Could this method be used to measure Fuel Injector Current draw at the wire of the injector?
I have never tried that approach but I don't think it would work real well. I'm thinking there wouldn't be the same amount of load on the source as there is with the starter. Use a low amp clamp for the best results, and place your clamp at the fuse that powers all the injectors to see them in one capture.
Snapon modis edge scope work for this?
Absolutely!
Say your using a snap on verus edge instead of swapping polarity could you just use the invert waveform feature 🤔
Absolutely! On any scope with an invert function!
Hello, Pete. Would you recommend an Amp clamp with a multimeter? I have never seen you use one?
I've had issues with an amp clamp on a multimeter, especially when looking for very low current draws. Noise from the overhead lighting in the shop, meter sample rate and accuracy are a few of the reasons I prefer to use a scope with my amp clamp.
I was just asking because I have a pico scope and I would like to use an inexpensive amp clamp.
Check with the folks at AESWave.com. They have a selection of amp clamps - high, low and micro - that would be great fits for your Pico
I am a bit confused. Should I simply hook my scope on battery terminals for a voltage change measurement or AC Coupling is something special?
If you want to get a pattern similar to the current pattern most relative compression waveforms show, simply invert the pattern OR switch the leads (pos to neg, neg to pos). No need for AC coupling.
When I swapped polarity my oscilloscope blew up
What brand did you have, and how did you attach it?
@@MotorAgeMagazinePicoscope I had channel A for trigger from coil on plug signal wire with ground strap connected to BATT-, channel B connected to battery with reverse polarity. As soon as I touch the alligator clip from channel be to the Batt+ it shorted and smoked my test leads and scope
@@namechane1758 Did I read that correctly? You had channel A ground to B- and channel B ground to B+?
@@MotorAgeMagazine So, is the answer that you can't set up a reference channel to an ignition event if you're using reverse polarity on your relative compression test?
@@mahlerob All channels must be ground referenced the same. If you want to add an ignition reference, I would recommend setting up your scope normally and using the invert function to flip the battery voltage capture. Make sense?
I don’t find this helpful, because you did not demonstrate it. Some of us want to see action