Help regarding PH sensor

I am currently using this board. Sensor de pH Arduino / Medidor de pH + Módulo de Leitura - Usinainfo

I’ve tried this code to run my Ph sensor.

#define SensorPin 0          // the pH meter Analog output is connected with the Arduino’s Analog
unsigned long int avgValue;  //Store the average value of the sensor feedback
float b;
int buf[10],temp;

void setup()
{
  pinMode(13,OUTPUT);  
  Serial.begin(9600);  
  Serial.println("Ready");    //Test the serial monitor
}
void loop()
{
  for(int i=0;i<10;i++)       //Get 10 sample value from the sensor for smooth the value
  { 
    buf[i]=analogRead(SensorPin);
    delay(10);
  }
  for(int i=0;i<9;i++)        //sort the analog from small to large
  {
    for(int j=i+1;j<10;j++)
    {
      if(buf[i]>buf[j])
      {
        temp=buf[i];
        buf[i]=buf[j];
        buf[j]=temp;
      }
    }
  }
  avgValue=0;
  for(int i=2;i<8;i++)                      //take the average value of 6 center sample
    avgValue+=buf[i];
  float phValue=(float)avgValue*5.0/1024/6; //convert the analog into millivolt
  phValue=3.5*phValue;                      //convert the millivolt into pH value
  Serial.print("    pH:");  
  Serial.print(phValue,2);
  Serial.println(" ");
  digitalWrite(13, HIGH);       
  delay(800);
  digitalWrite(13, LOW); 

}

When I connect the VCC pin to arduino 5v it gives the result [Ph: 17.48] while not dipped into any liquid. Isn’t it supposed to give PH readings around 5 to 8. Dipping the sensor into the water is also not chaning any value.

Can anyone help me regarding how to get the correct PH value I can’t find anything helpful in the internet.

What is the actual voltage you measure on the A0 pin with your multimeter? Is it what you expect? If not, check your wiring: make sure the sensor actually has power, and that there’s a reasonable voltage at its output pin. This should be the same as what you measure at the input of the Arduino.

What is the actual analogRead() value you get when sampling that voltage? Is it what you expect based on the result of the first measurement?

Make sure those readings are correct before trying to do the math.