Reading signal frequency

Using Arduino Programming Questions
2

What are the intervals for frequencies do you use?

Try this:

#include <FreqMeasure.h>

void setup()   /*----( SETUP: RUNS ONCE )----*/
{
  Serial.begin(14400);
  FreqMeasure.begin();
}/*--(end setup )---*/

double sum=0;
int count=0;

void loop() {
  if (FreqMeasure.available()) {
    // average several reading together
    sum = sum + FreqMeasure.read();
    count = count + 1;
    if (count > 30) {
      double frequency = F_CPU / (sum / count);

      unsigned long speeding = (frequency*0.3)/2; // calculate speed
      Serial.print("Freq:");
      Serial.print(frequency);
      Serial.print("       ");
      delay(5000);
      sum = 0;
      count = 0;
    }
  }

}