About Analog Electrical Conductivity Meter (SKU: DFR0300)

// # 
// # Editor     : YouYou from DFRobot
// # Date       : 23.04.2014
// # E-Mail   : [email protected]

// # Product name: Analog EC Meter
// # Product SKU : DFR0300
// # Version     : 1.0

// # Description:
// # Sample code for testing the EC meter and get the data feedback from the Arduino Serial Monitor.

// # Connection:
// #        EC meter output     -> Analog pin 1
// #        DS18B20 digital pin -> Digital pin 2
// #

#include <OneWire.h>

#define StartConvert 0
#define ReadTemperature 1

const byte numReadings = 20;     //the number of sample times
byte ECsensorPin = A1;  //EC Meter analog output,pin on analog 1
byte DS18B20_Pin = 2; //DS18B20 signal, pin on digital 2
unsigned int AnalogSampleInterval=25,printInterval=700,tempSampleInterval=850;  //analog sample interval;serial print interval;temperature sample interval
unsigned int readings[numReadings];      // the readings from the analog input
byte index = 0;                  // the index of the current reading
unsigned long AnalogValueTotal = 0;                  // the running total
unsigned int AnalogAverage = 0,averageVoltage=0;                // the average
unsigned long AnalogSampleTime,printTime,tempSampleTime;
float temperature,ECcurrent; 
 
//Temperature chip i/o
OneWire ds(DS18B20_Pin);  // on digital pin 2

void setup() {
 // initialize serial communication with computer:
  Serial.begin(115200);
  // initialize all the readings to 0:
  for (byte thisReading = 0; thisReading < numReadings; thisReading++)
    readings[thisReading] = 0;
  TempProcess(StartConvert);   //let the DS18B20 start the convert
  AnalogSampleTime=millis();
  printTime=millis();
  tempSampleTime=millis();
}

void loop() {
  /*
   Every once in a while,sample the analog value and calculate the average.
  */
  if(millis()-AnalogSampleTime>=AnalogSampleInterval)  
  {
    AnalogSampleTime=millis();
     // subtract the last reading:
    AnalogValueTotal = AnalogValueTotal - readings[index];
    // read from the sensor:
    readings[index] = analogRead(ECsensorPin);
    // add the reading to the total:
    AnalogValueTotal = AnalogValueTotal + readings[index];
    // advance to the next position in the array:
    index = index + 1;
    // if we're at the end of the array...
    if (index >= numReadings)
    // ...wrap around to the beginning:
    index = 0;
    // calculate the average:
    AnalogAverage = AnalogValueTotal / numReadings;
  }
  /*
   Every once in a while,MCU read the temperature from the DS18B20 and then let the DS18B20 start the convert.
   Attention:The interval between start the convert and read the temperature should be greater than 750 millisecond,or the temperature is not accurate!
  */
   if(millis()-tempSampleTime>=tempSampleInterval) 
  {
    tempSampleTime=millis();
    temperature = TempProcess(ReadTemperature);  // read the current temperature from the  DS18B20
    TempProcess(StartConvert);                   //after the reading,start the convert for next reading
  }
   /*
   Every once in a while,print the information on the serial monitor.
  */
  if(millis()-printTime>=printInterval)
  {
    printTime=millis();
    averageVoltage=AnalogAverage*(float)5000/1024;
    Serial.print("Analog value:");
    Serial.print(AnalogAverage);   //analog average,from 0 to 1023
    Serial.print("    Voltage:");
    Serial.print(averageVoltage);  //millivolt average,from 0mv to 4995mV
    Serial.print("mV    ");
    Serial.print("temp:");
    Serial.print(temperature);    //current temperature
    Serial.print("^C     EC:");
    
    float TempCoefficient=1.0+0.0185*(temperature-25.0);    //temperature compensation formula: fFinalResult(25^C) = fFinalResult(current)/(1.0+0.0185*(fTP-25.0));
    float CoefficientVolatge=(float)averageVoltage/TempCoefficient;   
    if(CoefficientVolatge<150)Serial.println("No solution!");   //25^C 1413us/cm<-->about 216mv  if the voltage(compensate)<150,that is <1ms/cm,out of the range
    else if(CoefficientVolatge>3300)Serial.println("Out of the range!");  //>20ms/cm,out of the range
    else
    { 
      if(CoefficientVolatge<=448)ECcurrent=6.84*CoefficientVolatge-64.32;   //1ms/cm<EC<=3ms/cm
      else if(CoefficientVolatge<=1457)ECcurrent=6.98*CoefficientVolatge-127;  //3ms/cm<EC<=10ms/cm
      else ECcurrent=5.3*CoefficientVolatge+2278;                           //10ms/cm<EC<20ms/cm
      ECcurrent/=1000;    //convert us/cm to ms/cm
      Serial.print(ECcurrent,2);  //two decimal
      Serial.println("ms/cm");
    }
  }

}
/*
ch=0,let the DS18B20 start the convert;ch=1,MCU read the current temperature from the DS18B20.
*/
float TempProcess(bool ch)
{
  //returns the temperature from one DS18B20 in DEG Celsius
  static byte data[12];
  static byte addr[8];
  static float TemperatureSum;
  if(!ch){
          if ( !ds.search(addr)) {
              Serial.println("no more sensors on chain, reset search!");
              ds.reset_search();
              return 0;
          }      
          if ( OneWire::crc8( addr, 7) != addr[7]) {
              Serial.println("CRC is not valid!");
              return 0;
          }        
          if ( addr[0] != 0x10 && addr[0] != 0x28) {
              Serial.print("Device is not recognized!");
              return 0;
          }      
          ds.reset();
          ds.select(addr);
          ds.write(0x44,1); // start conversion, with parasite power on at the end
  }
  else{  
          byte present = ds.reset();
          ds.select(addr);    
          ds.write(0xBE); // Read Scratchpad            
          for (int i = 0; i < 9; i++) { // we need 9 bytes
            data[i] = ds.read();
          }         
          ds.reset_search();           
          byte MSB = data[1];
          byte LSB = data[0];        
          float tempRead = ((MSB << 8) | LSB); //using two's compliment
          TemperatureSum = tempRead / 16;
    }
          return TemperatureSum;  
}

 if(CoefficientVolatge<150)Serial.println("No solution!");   //25^C 1413us/cm<-->about 216mv  if the voltage(compensate)<150,that is <1ms/cm,out of the range