If you want to measure the speeds of the the rotating bodies, you may also adopt the following hardware scheme. In this scheme, 2 counters will be accumulating the pulses coming from 2 sensors; normalize the counts and then show the RPMs (RPM1, RPM2) on the LCD. The 3rd sensor will deliver its output to the UNO via interrupt; UNO will be counting the incoming pulses; normalize these counts and show RPM3 on the LCD. This scheme will also give you Real Time processing of the events. Your SD card has nicely been accommodated in the setup. Now, write codes; test the codes; post the codes for the learning of those who have been involved with this thread.