Ignition primary's and injector voltage

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Ignition primary's and injector voltage

Postby Guest » Sun Jul 01, 2007 11:28 am

Hi,
I have a 4 channel automotive kit, I want to be able to capture an ignition coil primary and injector voltage on road test.
Can someone suggest a "setting" i could use on the scope so that i can "capture" the point of misfire.
The ECU on this vehicle is turning off injector 4 (supposedly in response to a misfire) i want to be able to capture what happens just prior to the injector being switched off ! then return to the workshop and "replay/study" the capture. Is this possible ?

Regards all
Dave
Guest
 

recording

Postby Autonerdz » Sun Jul 01, 2007 5:10 pm

Hi Dave,

May I suggest primary voltage and current along with your injector and maybe the IC command. This would provide you will all the information about primary trigger and validate the primary drive as well.

You will want to be certain to use the 20:1 attenuators for the primary voltage and injector. You'll be looking at nearly 400 volts on the primary kick and 80 to 100 on the injector if it is not clipped. Always use the attenuators when you anticipate more than 50v inputs. If you got your kit from Autonerdz, you have an attenuator for each channel.

Dial samples up to the max and put lots of time on the screen. If using PicoScope 5, enable 'save on trigger' to record (this is broken in the latest 5.16.2 release of PicoScope 5 when using a 3000 series)

I suggest using PicoScope 6 for this task. It can maintain a much more robust sample rate at the longer time bases and no need to do a 'save on trigger' since it always is recording the last x number of screens.

High speed streaming mode in PicoScope 6 begins at 200ms/div. At this time base, with samples dialed up, you will sample at 1MHz per channel on each of the four channels with your 3423 scope. You can't do this with PicoScope 5.xx.

Another technique you can use is to repeat trigger on the injector kick. Since you know this signal fails, the scope will then stop recording when the injector is not firing. This can help you capture the event on a single screen.
Tom Roberts
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Postby Guest » Sun Jul 01, 2007 8:49 pm

Hi,
Thank you very much for your reply, very informative ! helps me a lot

Kind regards

Dave
Guest
 

welcome

Postby Autonerdz » Mon Jul 02, 2007 4:19 am

Your welcome, Dave. Glad I could help.

Be sure to visit The Autonerdz Community Forums too. We are a global cult of automotive lab scope diagnosticians sharing a wealth of information and discussion. Lots of Pico stuff too, of course :shock:
Tom Roberts
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