How to use NewPing sonar.ping_median(iterations) in multi-sensor?

[lladam]

Hi,
I am using 4 ultrasonic sensors in my project and NewPing method, can’t get the right readings, need help please.
Thank
Adam

// ---------------------------------------------------------------------------
// Example NewPing library sketch that pings 3 sensors 20 times a second.
// ---------------------------------------------------------------------------

#include <NewPing.h>

#define SONAR_NUM 3      // Number of sensors.
#define MAX_DISTANCE 200 // Maximum distance (in cm) to ping.

NewPing sonar[SONAR_NUM] = {   // Sensor object array.
  NewPing(2, 3, MAX_DISTANCE), // Each sensor's trigger pin, echo pin, and max distance to ping.
  NewPing(4, 5, MAX_DISTANCE),
  NewPing(7, 8, MAX_DISTANCE)
};

uint8_t duration[3] = {0};
uint8_t distance[3] = {0};

#define iterations 3      // Number of sensors.

void setup() {
  Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
  for (uint8_t i = 0; i < SONAR_NUM; i++) { // Loop through each sensor and display results.
    delay(50); // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
    Serial.print(i);
    Serial.print("=");
    Serial.print(sonar[i].ping_cm());
    Serial.println("cm ");
   
    duration[i] = sonar[i].ping_median(iterations);

    Serial.print("duration[i]=");
    Serial.println(duration[i]);

    distance[i] = (duration[i] / 29 / 2);

    Serial.print("distance[i]=");
    Serial.println(distance[i]);
  }
  // Serial.println();
}