Someone probably already mentioned this but what about using a dual-sensor system (similar to the missile defense idea - you don't declare that there are "incoming" until you see them by two independent sensor types). You could, for example, test to make sure that one of your electrodes is getting very hot (with a thermocouple) and also look for a characteristic spark spectrum with UV and optical sensors. You could possibly add a final voltage or current sensor which would look for the appropriate load (an arc has a negative differential resistance I think). This would be a third sensor. Another thought which occurred to me (this is probably too "out there" to be an easy solution) is whether there is actually some kind of fuel nozzle which somehow aerodynamically raises the temperature of the atomized mixture enough to guarantee ignition. Sean On Sun, Sep 12, 2010 at 8:58 PM, Dwayne Reid wrote= : > At 03:05 PM 9/12/2010, Brooke Clarke wrote: > >>If you're forced to use the spark you might use a HV cap to couple RF >>into a spectrum analyzer and see where there's a strong signal (you >>might force it using a tank circuit) and use the RF to confirm the spark. > > Yeah - I plan to look for multiple RF frequencies from the current > sensor on the ground electrode. > > I need to monitor the ground electrode so that an arc somewhere other > than to the ground electrode is ignored (fail-safe). =A0I'm planning to > monitor for multiple frequencies for a couple of reasons: > > 1) a false-positive on one frequency does not by itself decide that a > good spark exists. > > 2) I fully expect that at some point, switch-mode continuous spark > ignition systems will appear. =A0I don't want to be sampling that > frequency and thus get fooled by a short across the spark gap. > > Sampling multiple, non-harmonically-related frequencies solves both > of those problems. > > Again - thanks for the ideas! > > dwayne > > -- > Dwayne Reid =A0 > Trinity Electronics Systems Ltd =A0 =A0Edmonton, AB, CANADA > (780) 489-3199 voice =A0 =A0 =A0 =A0 =A0(780) 487-6397 fax > www.trinity-electronics.com > Custom Electronics Design and Manufacturing > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .