Warning! Technical read to help sleeping patterns...
As you indicate Cam, front end circuitry, is as a guide, specific technology aligned. IIS was originally based around the VR sensor with a missing tooth gear wheel, assigned to crank or cam timing in a 4 stroke motor, IIS was also originally applied to my two stroke Suzuki GT750, as a "CDI".
Missing tooth also incorporated a trial of optical high resolution encoder wheel from HP and a slotted precision opto sensor to decode the position of the segments, as many as 256 ( or 360/1024 from memory ) 256 aligns to 8 bits while 360 required 9 bits, 1024 10 bits, was also a quad output device so could encode forward and reverse shaft direction. Cumbersome to deal with a Uprocc of 8 bits architecture, simplified. Also on the optical precise disc was an index tract, very clever and while not very expensive, the project was getting complicated.
Jump forward, slotted simple opto coupler was produced for road trials, iis was designed on a hard segment for trigger event, while other opticals ( Lumention for one ) and DMC, this technique has a major design flaw in my view, the sensor transistor was cut off most of the rotation, then illuminated for the trigger event, leaving the signal line back to the ignition module susceptible to external electrical interference. The obvious methodology is too invert that function, "grounding" the sense wire(s) back to the module and hence far less susceptible to external noise. My background included design and calibration of Oil refinery metering equipment, erroneous signals a no no.
Off we went, simple slotted opto and the reports were positive. Yet i knew an optical device is not best for reliability inside a crank case cover or indeed oil ( ducati VR's live in the engine oil bathing ). Fabricated an intermediate opto to Hall Effect encoder pcb, the slotted opto had a NPN transistor buffering the output to ignition module. I could then test the module front end to be the final Hall Effect IIS, all the while using the slotted opto option while the new HE pcb was designed and field proven, first with Neodymium Curie Point was too low, then onto Samarium Cobolt.
Stayed with Unipolar HE devices while others chose Bipolar or latching, that was the final design, however the iis used current sense switching not voltage. This allowed for maximum EMI robustness in crank encoder to module wiring, did not use 4-20ma loop rather just a 0-20mA loop circuitry, which for little reduction in reliability a visual led for each sensor including TDC on the crank pcb, and a further opto coupler at the module end, ensuring maximum interference robustness. Being current triggered, no loss of sense voltage mattered overall.
A slotted opto had purpose for initial R and D plus assessment pending properly engineered robust technology as HE offered in all matters. HTH j.
