PT100.cpp

/*
  PT100.cpp - Library for measuring temperature with a PT100.
  Created by João Lino, June 24, 2015.
  Released into the public domain.
*/
#include "Arduino.h"
#include "PT100.h"

PT100::PT100(char *name,
                    int OutputPin_SensorPower, 
                    int InputPin_TemperatureReading, 
					int TimeBetweenReadings, 
					float ADCVmax, 
					float Vs,
					float R1) {
	
    _name                              =   name;
    _OutputPin_SensorPower             =   OutputPin_SensorPower;
    _InputPin_TemperatureReading       =   InputPin_TemperatureReading;
	_TimeBetweenReadings               =   TimeBetweenReadings;
	_ADCVmax                           =   ADCVmax;
	_Vs                                =   Vs;
	_R1                                =   R1;
	
	_temperatureAverage	               =   24.0;
	_measuredTemperature               =   24.0;
	_lastTemperatureRead               =   0;
	_VoutAnalogSample                  =   -1;
	_VoutPreviousAnalogSample          =   -1.0;
	_temperatureMeasurementsMarker     =   0;
    _rPT100MeasurementsMarker          =   0;
    _measuredTemperatureDeviation      =   0.0;
    _sampleDeviation                   =   0.0;

    analogReference(INTERNAL1V1);									// EXTERNAL && INTERNAL2V56 && INTERNAL1V1
    pinMode(_OutputPin_SensorPower, OUTPUT);            // setup temperature sensor input pin
    digitalWrite(_OutputPin_SensorPower, LOW);      // initialize sensor on
}

void PT100::setPower(float ADCVmax, float Vs) {
    _ADCVmax                           =   ADCVmax;
    _Vs                                =   Vs;
}

void PT100::safeHardwarePowerOff() {
  digitalWrite(_OutputPin_SensorPower, LOW);        // Turn temperature sensor OFF for safety
}

void PT100::measure(boolean ln) {
  if(millis() - _lastTemperatureRead >= _TimeBetweenReadings) {                           //time to measure temperature
    
    /** measure Vout analog sample */
    digitalWrite(_OutputPin_SensorPower, HIGH);      // initialize sensor on
    delay(10);
    _VoutAnalogSample = analogRead(_InputPin_TemperatureReading) + _sampleDeviation;     // Get a reading
    digitalWrite(_OutputPin_SensorPower, LOW);      // initialize sensor on

    _lastTemperatureRead            = millis();                                             // Mark time of temperature reading

    _rPT100MeasurementsMarker++;                                                                                                                                                   // Position reading buffer marker at the last updated position
    if(_rPT100MeasurementsMarker >= TEMPERATURE_AVERAGE_VALUE_I) _rPT100MeasurementsMarker = 0;           // Check that it has not gone out of the buffer range
    _rPT100Measurements[_rPT100MeasurementsMarker] = _VoutAnalogSample;
    float Vout = GetMedian(_rPT100Measurements) * _ADCVmax / CONSTANT_ADC_STEP_COUNT;
    float Rx = _R1 / ( _Vs / Vout - 1.0);

    /** Calculate temperature value */
    _measuredTemperature = 1.08271 * pow(10.0, -13.0) * (3.12508 * pow(10.0, 16.0) - 5.65566 * pow(10.0, 6.0) * sqrt(3.51501 * pow(10.0, 19.0) - 4.61805 * pow(10.0, 16.0) * Rx));

    #ifdef DEBUG
    Serial.print(_name);
    Serial.print(",");
    //Serial.print(_VoutAnalogSample);
    Serial.print(GetMedian(_rPT100Measurements));
    Serial.print(",");

    if(ln) Serial.println("");
    #endif
  }
}

float PT100::GetMedian(int array[]){
    int sorted[TEMPERATURE_AVERAGE_VALUE_I];
    float value = 0.0;

    for(int x = 0; x < TEMPERATURE_AVERAGE_VALUE_I; x++) {
        sorted[x] = array[x];
    }

     //ARRANGE VALUES
    for(int x = 0; x < TEMPERATURE_AVERAGE_VALUE_I; x++){
        for(int y = 0; y < TEMPERATURE_AVERAGE_VALUE_I - 1; y++){
            if(sorted[y]>sorted[y+1]){
                int temp = sorted[y+1];
                sorted[y+1] = sorted[y];
                sorted[y] = temp;
            }
        }
    }

    //CALCULATE THE MEDIAN (middle number)
    if(TEMPERATURE_AVERAGE_VALUE_I % 2 != 0){// is the # of elements odd?
        int temp = ((TEMPERATURE_AVERAGE_VALUE_I+1)/2)-1;
        value = (float) sorted[temp];
    }
    else{// then it's even! :)
        value = ((float) ( sorted[(TEMPERATURE_AVERAGE_VALUE_I/2)-1] + sorted[TEMPERATURE_AVERAGE_VALUE_I/2] )) / 2.0;
    }

    return value;
}

float PT100::GetMode(float new_array[]) {
    int ipRepetition[TEMPERATURE_AVERAGE_VALUE_I];
    for (int i = 0; i < TEMPERATURE_AVERAGE_VALUE_I; i++) {
        ipRepetition[i] = 0;//initialize each element to 0
        int j = 0;//
        while ((j < i) && (new_array[i] != new_array[j])) {
            if (new_array[i] != new_array[j]) {
                j++;
            }
        }
        (ipRepetition[j])++;
    }
    int iMaxRepeat = 0;
    for (int i = 1; i < TEMPERATURE_AVERAGE_VALUE_I; i++) {
        if (ipRepetition[i] > ipRepetition[iMaxRepeat]) {
            iMaxRepeat = i;
        }
    }

    return new_array[iMaxRepeat];
}

float PT100::getCurrentTemperature() {
    return _measuredTemperature + _measuredTemperatureDeviation; // - 4.41;
}

float PT100::getMeasuredTemperatureDeviation() {
    return _measuredTemperatureDeviation; // - 4.41;
}
float PT100::setMeasuredTemperatureDeviation( float measuredTemperatureDeviation) {
    if( _measuredTemperatureDeviation != measuredTemperatureDeviation ) {
        _measuredTemperatureDeviation = measuredTemperatureDeviation;

        for( int i = 0; i < TEMPERATURE_AVERAGE_VALUE_I; i++ ) {
            _temperatureMeasurements[i] = _temperatureMeasurements[i] + ( _measuredTemperatureDeviation * -1 );
        }
    }
    
    return _measuredTemperatureDeviation; // - 4.41;
}

float PT100::setSampleDeviation( float sampleDeviation) {
    _sampleDeviation = sampleDeviation;

    return _sampleDeviation;
}