http://www.home.earthlink.net/~bkwhite54/id1.html

That link up there is for my web page and I have posted a waveform in it which has me puzzled.
The waveform in question is the secondary shot, ( lower on page ).
Can anyone explain what is going on at the .4 and.5 sec areas ?
This engine had a known problem of over rich fuel mix and the plugs were fouled and miss firing with very low firing voltages so I set the trigger to 1 KV, I think that explains the noise at the base of the waveform.
On this same vehicle I had a capture of the secondary at the coil wire with at least two or three spark events contained in that downward sloping line as shown at the .4 and .5 sec area.
Is the carbon fouling in the plugs acting as a capacitor and it takes that capacitance that long to dissipate ?
I have never seen ignition waveforms as precise as are displayed by the Pico Scope.

Brad White

I have a couple of questions if you do not mind

What engine and type of ignition system is this?

What pico are you using?  What mode and how many samples requested on this wave.The reason I ask is the timebase of  200ms a division is probably not best to view seccondary and it may be pushing the pico beyond its limits.

When I want to look at seccondary I usually use the save on trigger function so I can have better information usually the highest I go is about 20ms a division on a 8cyl this will usually show a full revolution.

Hi Brad,

Sam's right.  That's way beyond the limits of your 212/3 for secondary acquisition.

Even if you had your samples dialed up to the max 32,000 in block mode, the samples would be 85 microseconds apart.  

At 10ms/div they would be 5 microseconds apart.  A secondary firing line is about 10 microseconds, so more time than that will not reliably capture them.

You can do the calculations yourself with our sample rate calculator:

http://www.autonerdz.com/java/SampleRateCalculator.html

The 212/3 is still more powerful than most of the automotive scopes in use today but everything has it's limits.

The PicoScope 3000 series has it's limits too.  These are the most powerful automotive scopes available right now.  Even if you were using one of these with one channel deployed at 200ms/div, the samples would be 6 microseconds apart.  This would reliably capture the firing KV events, but that would be the limit.  After all, that's two seconds of time on the screen  :o

Thanks gang, I am not used to all this modern technology and sometimes I get lost.
It took me about an hour to figure out how to do a composite page but now I think I have it.
I'll read that web page of yours Tom and try to remember as much as I can because this Pico Scope is Great.
I used a Mac Quick Scope for years and never realized what I was missing.

Brad White.