counting pulses from an encoder 0-7,5 V

This is my VI and my signal measurement:

[IMG]http://i.imgur.com/mfttanz.png[/IMG]

How can I count the pulses from the encoder with this VI? I want to count it like in this VI:

[IMG]http://i.imgur.com/xRzz0Lr.jpg[/IMG]

So that I can measure the angle of a motor-driven frame using a 24 VDc motor.