Secondary ignition

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Mark J

Secondary ignition

Post by Mark J » Sun Dec 15, 2002 3:33 pm


I am trying to map the advance curve on my Race bike prior to modifying the ignition curve. I am doing this using an ADC11 and will use the fastblock converter to catch and log the trace at a reasonable rate. To do this I have a little box that combines the signal from the inductive pickup and the signal from the HT and passes it to Ch1 (fastblock only works on a single channel). Advance should be the time difference from signal from inductive pickup and that from secondary ignition. Should be simple - except...
I can't get a reliable signal from the secondary pickup connection. I am using a MI074 secondary ignition pickup. Is there a trick to using this? I have only managed to get a proper trace once all other times it is as if the unit is not coupling properly? (This occurs also when I connect directly to the ADC 11 and don't go via my box)
Any advice/help gratefully appreciated

Mark J

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Joined: Wed Sep 25, 2002 9:35 am
Location: Cambridgeshire, UK

Post by matthew » Mon Dec 16, 2002 10:58 am


Sorry to hear you're having problems with this. I'm sorry to say that, ignition spikes are too thin for the ADC-11 unit to detect.

The ADC-11 can achieve 10,000 Samples per second in Fast-block mode. Which equates to 100us; an ignition spike only has a width of about 20us. This means that the software is likely to miss the trigger point although occasionally it will hit it (which explains why you have achieved one trace).

If the wave form has a leading edge which remains elevated (ie - it stays above 2kV throughout the duration of the ignition signal, like this one), then you could trigger off a much lower threshold ... but bear in mind that your readings will always have an error up to 100us, and you are unlikely to see the spike on your screen.

(The recommended Automotive unit is the ADC-212/3, which is more than capable of triggering off the trace in question).

Best Regards,
Matt Everett

Pico Software Engineer

Mark J

Post by Mark J » Tue Dec 17, 2002 7:37 am


Thanks, must have dropped a decimal place :oops: .....

Mark J

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