#define SensorPin A2 //pH meter Analog output to Arduino Analog Input 2 #define Offset 0.00 //deviation compensate #define LED 13 #define samplingInterval 20 #define printInterval 800 #define ArrayLenth 40 //times of collection int pHArray[ArrayLenth]; //Store the average value of the sensor feedback int pHArrayIndex=0; void setup(void) { pinMode(LED,OUTPUT); Serial.begin(9600); Serial.println("pH meter experiment!"); //Test the serial monitor } void loop(void) { static unsigned long samplingTime = millis(); static unsigned long printTime = millis(); static float pHValue,voltage; if(millis()-samplingTime > samplingInterval) { pHArray[pHArrayIndex++]=analogRead(SensorPin); if(pHArrayIndex==ArrayLenth)pHArrayIndex=0; voltage = avergearray(pHArray, ArrayLenth)*5.0/1024; pHValue = 3.5*voltage+Offset; samplingTime=millis(); } if(millis() - printTime > printInterval) //Every 800 milliseconds, print a numerical, convert the state of the LED indicator { Serial.print("Voltage:"); Serial.print(voltage,2); Serial.print(" pH value: "); Serial.println(pHValue,2); digitalWrite(LED,digitalRead(LED)^1); printTime=millis(); } } double avergearray(int* arr, int number){ int i; int max,min; double avg; long amount=0; if(number<=0){ Serial.println("Error number for the array to avraging!/n"); return 0; } if(number<5){ //less than 5, calculated directly statistics for(i=0;imax){ amount+=max; //arr>max max=arr[i]; }else{ amount+=arr[i]; //min<=arr<=max } }//if }//for avg = (double)amount/(number-2); }//if return avg; }