The Autonerdz Community Forums - Advice regarding scope wave forms

scopeman

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Advice regarding scope wave forms
Aug 9^th, 2016 at 2:14pm

Hi ,

I have just got hold of a 2 channel pico scope and was doing some tests to see how the scope is.
I have attached a screen shot of the waveform ,it's a primary ignition current (waste spark coil ) can anyone tell me why the middle of the ramp curves up then down ? car runs fine ..Is this ramp normal ?
Also have done a camshaft sensor test ...why does the square wave have the curves at the end are these a ground issue or normal noise ?

Thanks

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Vauxhall_Astra_2003_Petrol_20160809-0004.png (20 KB | 393 )

Vauxhall_Astra_20160809-0001.png (29 KB | 440 )

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scopeman Freshman Member Offline I'm an Autonerd Posts: 10 lancashire United Kingdom Gender:	Re: Advice regarding scope wave forms Reply #1 - Aug 10^th, 2016 at 5:16am Anyone any ideas as to why the wave forms have that spike on the ignition coil current and the the cam sensor curves after the trailing edge?
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Robski Guru Member Offline Posts: 262 Yorkshire Great Britain Gender:	Re: Advice regarding scope wave forms Reply #2 - Aug 10^th, 2016 at 7:39am which model scope ? where are you coupled for the CMP sensor ? include primary voltage with the coil current & repost. + car details ?
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scopeman Freshman Member Offline I'm an Autonerd Posts: 10 lancashire United Kingdom Gender:	Re: Advice regarding scope wave forms Reply #3 - Aug 10^th, 2016 at 11:01am Hi it's an old model 3223 2 channel ...cam sensor probes connected signal wire of cam and negative lead to battery ground.Current clamp was connected close to ignition coil feed .car is a 1.6 petrol vauxhall astra G 2003 z16se.
Back to top	Vauxhall_Astra_2003_Petrol_20160809-0004.psdata (3293 KB \| 266 ) IP Logged

scopeman Freshman Member Offline I'm an Autonerd Posts: 10 lancashire United Kingdom Gender:	Re: Advice regarding scope wave forms Reply #4 - Aug 10^th, 2016 at 11:02am second image posted is the original file as in previous post.. Car runs fine..just wanting to know that the scope is fine as only just got it.Did injector voltage and current wave form and they look OK .Just not sure about the images i posted.
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Tom Roberts

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Re: Advice regarding scope wave forms
Reply #5 - Aug 11^th, 2016 at 8:32am

scopeman wrote on Aug 10^th, 2016 at 11:02am:

just wanting to know that the scope is fine as only just got it.

I don't see anything there that would make me suspect you have a scope problem.

The first image looks like you may have more than one component down the line from your current probe test point.

The second one looks like voltage drops caused by the coil current loads.

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Tom Roberts
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scopeman

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Re: Advice regarding scope wave forms
Reply #6 - Aug 11^th, 2016 at 9:32am

Tom Roberts wrote on Aug 11^th, 2016 at 8:32am:

scopeman wrote on Aug 10^th, 2016 at 11:02am:

just wanting to know that the scope is fine as only just got it.

I don't see anything there that would make me suspect you have a scope problem.

The first image looks like you may have more than one component down the line from your current probe test point.

The second one looks like voltage drops caused by the coil current loads.

Hi Thanks Tom for the reply.I changed the usb lead and re scoped the cam and coil today.Both wave forms look good now so hopefully resolved.Attached new files below.

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Vauxhall_Astra_2003_Petrol_cam_filter_applied-0002.psdata (5068 KB | 343 )

Vauxhall_Astra_2003_Petrol_cam_no__filter-0003.psdata (5069 KB | 316 )

Vauxhall_Astra_2003_Petrol_coil_primary_current_2-0007.psdata (4102 KB | 305 )

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Tom Roberts Autonerdz Administrator Picogroup Offline Autonerdz Founder Posts: 8,595 Olympia Washington USA Gender:	Re: Advice regarding scope wave forms Reply #7 - Aug 11^th, 2016 at 10:12am scopeman wrote on Aug 11^th, 2016 at 9:32am: I changed the usb lead and re scoped the cam and coil I can't explain that. Makes no sense to me. I suspect something else changed as well.
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scopeman

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Re: Advice regarding scope wave forms
Reply #8 - Aug 11^th, 2016 at 11:56am

Tom Roberts wrote on Aug 11^th, 2016 at 10:12am:

scopeman wrote on Aug 11^th, 2016 at 9:32am:

I changed the usb lead and re scoped the cam and coil

I can't explain that. Makes no sense to me. I suspect something else changed as well.

This is what baffled me as i connected everything the same way with same settings but different usb lead .Could be that the other usb lead was intermittent as scope was on front passenger seat with my laptop? not really sure but like i said as soon as i set up this morning i got the waveforms without any problems.What do you think could have changed as leads and clamp were in same position as yesterday and used same pre set settings on the scope.Will be trying some more tests tomorrow if weather persists.

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scopeman

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Re: Advice regarding scope wave forms
Reply #9 - Aug 12^th, 2016 at 10:10am

Well , have been testing today and i now know that the usb lead is intermittent as i used the old one and after wiggling it some of the signals were acting up so swapped back to the good one and all was fine.Also i experimented with moving the leads closer to other components and got some interference when doing so,so i might not have put the leads in the exact same position when i tested . Seems the usb cable may have masked other issues . Just glad the scope is fine and working . Wink

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scopeman Freshman Member Offline I'm an Autonerd Posts: 10 lancashire United Kingdom Gender:	Re: Advice regarding scope wave forms Reply #10 - Aug 12^th, 2016 at 10:16am While on this thread does anyone know how to be able to open the compression test files.I I did the test today but cannot open the file ,it says pddata?
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Andrew Phoenix

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Re: Advice regarding scope wave forms
Reply #11 - Aug 12^th, 2016 at 12:46pm

scopeman wrote on Aug 12^th, 2016 at 10:16am:

While on this thread does anyone know how to be able to open the compression test files.I I did the test today but cannot open the file ,it says pddata?

Are you attempting to open it with PicoScope 6? pddata files are for Pico Diagnostics. It's easiest to open PD and click 'load' from the File menu.

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Have you tried turning it off and on again?

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scopeman

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Re: Advice regarding scope wave forms
Reply #12 - Aug 13^th, 2016 at 6:32am

Andrew Phoenix wrote on Aug 12^th, 2016 at 12:46pm:

scopeman wrote on Aug 12^th, 2016 at 10:16am:

While on this thread does anyone know how to be able to open the compression test files.I I did the test today but cannot open the file ,it says pddata?

Are you attempting to open it with PicoScope 6? pddata files are for Pico Diagnostics. It's easiest to open PD and click 'load' from the File menu.

Hi yes i i have tried to open it with pico 6 and also with the pico diagnostics that i downloaded to do the test with. . This is the error i get " value cannot be null.parameter name.source"

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