New to secondary ignition scoping, some questions

Hi, I just started scoping the secondary since it provides lots of information from what I've seen, first this forum provides a lot of good info about actual testing and not just reference and perfectly centered/shaped waveforms, I kinda know what to look now that I started checking on the car I found some (normal) signals.

First it's a DIS, V6 engine Coilpack, wasted spark system, I'm using a hantek setup (non automotive), ht25 probe, so what I found and at the beginning threw me off is that the coil towers are inverted (on each pair, left side puts the negative spark and right side the positive)?

Example, coils are arranged like this

Coil A: Cyl 1-4
Coil B: Cyl 2-5
Coil C: Cyl 3-6

So I started scoping from cylinder 5, it was just at the middle and more exposed, I got the classic waveform jumping all around, set my trigger and time scale, it's stable looks kinda ok, lets try another cylinder from the same front bank (1-3-5), number 1 doesn't trigger anything, well let's try number 3, same, went back to number 5 and I got the previous waveform, so I get the trigger down and I can see the inverted waveform, I thought that was for the wasted exhaust spark so where is my power stroke positive spark? 

I was expecting to see the wasted spark always negative independent of what cable I'm scoping, so the job would be just as easy as setting the right trigger for the positive spark and just put the probe on the other wires but with this system the left side of the coil tower (1, 2, 3) puts the negative spark @ the power stroke while the right side (4, 5, 6) fires a positive spark.

So in order to correctly measure this kind of system I have to measure the positive sparks with the trigger set to the fire line for the right sides of the tower (4, 5, 6)  and for the left side (1, 2, 3) I have to invert the reading to get the negative ones and that is my power stroke spark?

Sorry if this is really noob question 

 

Wether the secondary will show up as :negative/upside down or as positive/upside up depends on the direction of the current flow. This direction does not change within the same cylinder, it is the same during the waste spark event as it is during the power spark event. So yes,  you visualize all the negative firing cylinders with the same scope settings but you'll need them to reconfigure to get the positive fired ones shown on the screen. If you put sufficient time on the screen you will be able to distinguish waste spark from power spark in the same capture.

What scope exactly are you using? My guess is unfortunately the scope and its software is pretty finite for what you're trying to achieve: putting more time on the screen will force the hardware beyond it's limit to show a reliable waveform. The invert function seems to lack functionality with regards to the trigger settings in inverse mode.

You may want to try the 'open hantek' software as this probably will yield better results than the one that comes with the scope originally.

Hi, thank you for your response, that makes total sense, I don't why I was expecting a power stroke spark as positive and the exhaust/wasted spark as negative, but now I get it, I'm using a hantek 6022BL, the official hantek software is really bad, I had a bad time trying to get the signature from the probe, but now I switched to the OpenHantek, now the issue I think it's related to the trigger (it lacks a hardware trigger), if I put the trigger at the fire kv level it doesn't trigger too often, I had to lower the trigger to the top of the remaining oscillations and the wasted spark is also caught by the trigger, here I start looking at the positive spark cylinders, 4, 5, 6, then I switch to the negative ones and invert the signal, then I try to improve the triggering setup but that were the limitations show up, I heard good things about the HScope with the automotive module, have you guys tried that one?

Also I was hoping to set the trigger to x10000 since that is the attenuation setup from that x25 probe but I don't see that scale in openHantek and I think I get a better reading with just setting the x1 and 200mv range.

You´ll find some information on the Hscope in this thread:

www.scannerdanner.com/forum/diagnostic-t...cording.html?start=0

The jitter on the trigger is due to the deficient sample rate: the displayed sample rate of 500 k samples/sec translates into 10000 sampling points on your screen with the 2ms/div setting. This is too little for capturing all relevant events within the 20ms overall screentime. So sometimes you/the scope gets lucky and other times not so much....

To capture an inverted wave form properly really needs a falling trigger.