Arduino, Vibration Sensor SW420

Example Code
int pin_LED = 13;
int pin_EP = 9;

void setup() {
    Serial.begin(9600);
    pinMode (pin_LED, OUTPUT);
    pinMode (pin_EP, INPUT); //set EP input for measurment
}

void loop() {
    long measurement = TP_init(); //Vibration sensor.
    delay(50); // default is 50
    Serial.print( "key U:" ); Serial.print( " [" ); Serial.print( measurement ); Serial.print( "] " );

    if (measurement > 500){
            digitalWrite(pin_LED, HIGH);
            Serial.print( "Vibration Level: Earthquake." );

    } else if (measurement > 100){
            digitalWrite(pin_LED, HIGH);
            Serial.print( "Vibration Level: Shake Tea." );
            digitalWrite(pin_LED, LOW);
    } else {
            digitalWrite(pin_LED, LOW);
            Serial.print( "Vibration Level: Very Quiet." );
    }
}

long TP_init(){
    delay(10); // default is 10
    long measurement=pulseIn (pin_EP, HIGH); //wait for the pin to get HIGH and returns measurement
    return measurement;
}