#define AVG_COUNT 3

////These are the variables used for the first tacho.
unsigned long last_pulse_time_1; //time of the last measured pulse, from startup.
int interval_index_1;
unsigned long inverval_1[AVG_COUNT];
unsigned long num_pulses_1;

void pulse_1()
{
  unsigned long current_time = millis() //store the current time.
  interval_index_1 ++;
  if(interval_index_1 >= AVG_COUNT)
    interval_index_1 = 0;
  interval_1[interval_index_1] = current_time - last_pulse_time_1;
  last_pulse_time_1 = current_time;
  num_pulses_1 ++;
}