Do we need frequency to voltage converter to connect photo interrupter to NI myDAQ

[sushanth.raj]

i need to find the RPM of a motor using photo interrupter and NI myDAQ. Do we need frequency to voltage convertor for it. If yes were can i find the correct circuit for it.

[NIquist]

That could work but if you have a digital in on your MyDAQ it would be easier to read the pulses and convert them to frequency in software.  DAQmx read has that functionality built in (Counter > Single Sample > Pulse Frequency)