This meter as regular tachometer measures the RPM of the DC motor displays the it in the LCD screen  with additional feature that we can inputting the desired RPM through the keypad then the Arduino  interfacing with motor driver makes the motor reaching the desired RPM using PID control .we can measure the the RPM of the motor with IR shaft encoder connected to interrupt pin "2"  when the motor rotates quarter of a turn the encoder the Arduino counts the turns and the time that the encoder takes to reaches this turn  .

This meter as regular tachometer measures the RPM of the DC motor displays the it in the LCD screen  with additional feature that we can inputting the desired RPM through the keypad then the Arduino  interfacing with motor driver makes the motor reaching the desired RPM using PID control .
we can measure the the RPM of the motor with IR shaft encoder connected to interrupt pin "2"  when the motor rotates quarter of a turn the encoder the Arduino counts the turns and the time that the encoder takes to reaches this turn  .