Repl cone/wheel for optical tachometer

This pocket sized 6-digit LCD optical tachometer has a measuring range of 30 to 30000 rpm. The unit operates by sensing reflected light from an integral source, and will sense any rotating shaft if there is sufficient contrast e.g. a keyway. Alternatively self-adhesive reflectors may be affixed to the shaft. Requires 4 x AAA size alkaline batteries (not supplied).