float calibration = 21.24;
const int analogInPin = A1;
int sensorValue = 0;
unsigned long int avgValue;
float b;
int buf[10],temp;
void setup() {
 analogReference(DEFAULT);
 Serial.begin(9600);
}

void loop() {
 for(int i=0;i<10;i++)
 {
 buf[i]=analogRead(analogInPin);
 delay(30);
 }
 for(int i=0;i<9;i++)
 {
 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++)
 avgValue+=buf[i];
 float pHVol=(float)avgValue*4.5/1000/6;
 Serial.print("phvol = ");
 Serial.println(pHVol);
 float phValue = -5.70 * pHVol + calibration;
Serial.print("sensor = ");
 Serial.println(phValue);
 delay(500);
}