Can anyone explain how the tech reader works on a PS 2.
i understand it reads the sold black dashes on the flywheel however how does it do this?
thanks
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The reader is a reflective sensor, it has an IR emitter and an IR receiver (photo transistor) in a single package. When you look closely at the face, you see two rectangular lenses, one is the IR emitter and the other is the IR receiver. The white stripes reflect back to the IR receiver and cause current to flow between the emitter and collector. The black stripes don't reflect much and very little current flows.
The reason so much is said about the spacing to the flywheel tape can be gleaned from the following response chart, at around .75mm from the tape is the maximum sensitivity.
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Thanks you are the best, not only do you know how but you know how to explain.
I greatly appreciate you sharing your knowledge.
I'm accomplished at looking things up. 
This just happens to be something that's in my wheelhouse since I actually designed a product using this very technology, the Chuff-Generator. I use the same kind of sensor on that as the one used for PS/2 tach reader boards.
AAMOF, I even made a replacement PS/2 tach reader board using a different but similar sensor as is used with the factory PS/2 tach reader. Replacement MTH DCS Tach Sensor Board
