I hope someone can shed some light on this. This is a capture from 1 cylinder on a waste spark ignition. The engine appears to run fine but I am confused as to why the firing voltage is so high unless I have my scope setup wrong. From my limited knowledge I think the rest of the pattern looks okay except the burn time is a little short. I don't see any indication that the fuel air ratio is out of the ball park. I also checked it on cranking with the plug leads grounded outside the engine via a .020" gap and the firing voltage is still high. Can anybody shed some light on this?

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James H wrote on Dec 10^th, 2016 at 9:34am:

The engine appears to run fine but I am confused as to why the firing voltage is so high unless I have my scope setup wrong.

James you need to select the Coloured Secondary Pos in the library.
Make sure you dont select the black probe.

Errr. Duh, Can't believe I missed that, If it seems impossible it is. lol

This is where the Probe is

Try the scope set up at 500ms/Div and the Sample Interval set at 6MS

This  will give you lots of time to see the changes in air fuel ratio across  the plug gap over time.

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Thanks Mike. There is hope yet. Does this all look normal to you?

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James H wrote on Dec 10^th, 2016 at 10:49am:

Thanks Mike. There is hope yet. Does this all look normal to you?

First of all turn the current probe around on the wire you have selected so as to see the current rise. ;)

I figure it was the current that the coil was drawing so I selected it as being a negative. 

How about this suggestion :)

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James H wrote on Dec 10^th, 2016 at 9:34am:

I hope someone can shed some light on this. This is a capture from 1 cylinder on a waste spark ignition. The engine appears to run fine but I am confused as to why the firing voltage is so high unless I have my scope setup wrong. From my limited knowledge I think the rest of the pattern looks okay except the burn time is a little short. I don't see any indication that the fuel air ratio is out of the ball park. I also checked it on cranking with the plug leads grounded outside the engine via a .020" gap and the firing voltage is still high. Can anybody shed some light on this?

I would agree and feel the burn time is borderline short in the capture you posted here in the opening post.

Thanks to both for the tips and suggestions. I tried the invert via the math channels Mike...neat

James H wrote on Dec 11^th, 2016 at 5:09am:

Thanks to both for the tips and suggestions. I tried the invert via the math channels Mike...neat

That's great.

Oh by the way there are a lot of Mikes on the forums but only one Mick ;)