Product information    
♦ Meeasures your RPM without need for installing magnets. Note: This version is for the eLogger
   V3 and the V2, which we have been selling since early 2006. The eLogger V2 has the large
   white letters "V2" (or "U2") on the bottom of the circuit board, near the RPM/Temp pins. 
   Click here for instruction manual. If you are not sure what eLogger version you have,
   order this optical sensor.