This Mitsu has a bit strange trigger type. It is hall, because of the three wires. The ignition is wasted spark, the trigger is Coil type, but alternating positive and negative to distinguish 1-4 and 2-3 cylinders. DC: ~2.5V, amplitude: ~2.5V. I recorded the trigger signal:
I process the signal with LM1815 with series condenser so it is theoretically universal considering trigger type (hall and VR). In 50% of cases, LCD displays right value, otherwise rough half of proper RPM. I thought about graetz but then I loose the information whether 1-4 or 2-3 cylinder needs spark.
Any ideas, how to condition the signal?
By the way, how to upload files to wiki? http://www.squirrelpf.com/msavr/upload.html is not working any more...