does this pertain to the spectrum optical sensor:
Installing the RPM Sensor in your ModelThe Optical RPM sensor should be installed so that its face (the flat part opposite the wiring) is
facing a spinning surface on your model, such as the prop hub, flywheel, spinner, axle, gear, etc.
The sensor’s face should be mounted so that it is about 2-4 mm from the spinning object. It is not
a bad idea to test the sensor at various distances using Live Mode (see your Recorder instruction
manual) to determine the best distance before permanently mounting the sensor, if this can be done
safely. The sensor can normally be glued into place, or mounted with heatshrink or tape to a selfconstructed
bracket (brass tubing usually works well), depending on where you are mounting it.
The surface to which the sensor is pointing should have alternating light and dark areas. The dark area must NOT be shiny or reflective. It should
be flat. For best results, half (180 degrees) of the surface should be light, and half should be dark. If you are mounting the sensor near a spinning
hub that is constructed light colored material , a black magic marker (if the result is not shiny), flat black paint, or flat black electrical tape can be
used to color half of the circumference black. Or, if you are mounting it next to dark colored spinning object (such as black plastic), you can use
white paint, white tape, or a white paint pen to make half of the circumference white. Note that if you are mounting on a black plastic spinning
object, make sure that the plastic is flat. It may be necessary to lightly sand it to take off any glossy surface.