Ponderings

Class Header

/*
PowerSignal.h - A simplistic way to represent a power signal for AC power monitoring
Author: peter c
*/

#ifndef PowerSignal_h
#define PowerSignal_h

#include "WProgram.h"
#include "ACSignal.h"

#define PS_DEGREES  1
#define PS_RADIANS 2

class PowerSignal
{
  public:
    PowerSignal(ACSignal& aVoltageSignal, ACSignal& aCurrentSignal);
    float computeApparentPower();
    float computeAveragePower();
    float computePowerFactor();
    float computePowerFactorAngle( int aMode );
    float computeReactivePower();
    void reset();
    void updateAccumulator();

private:
    ACSignal& mVoltageSignal;
    ACSignal& mCurrentSignal;
    float mSumVoltageTimesCurrent;
};

#endif

Class Body

/*
PowerSignal.cpp - Library doing basic signal calculations
Created by Peter Chrapchynski, December 11, 2009
*/

#include "WProgram.h"
#include "ACSignal.h"
#include "PowerSignal.h"

PowerSignal::PowerSignal(ACSignal& aVoltageSignal, ACSignal& aCurrentSignal):mVoltageSignal( aVoltageSignal ), mCurrentSignal( aCurrentSignal )
{
}

float PowerSignal::computeApparentPower()
{
  return ( mVoltageSignal.getRMSValue() * mCurrentSignal.getRMSValue() );
}

float PowerSignal::computePowerFactor()
{
  float l_powerFactor = 1.0;
  float l_apparentPower = computeApparentPower();

if( l_apparentPower > 0.01 )
    l_powerFactor =  computeAveragePower() / l_apparentPower;

return( l_powerFactor );
}

float PowerSignal::computePowerFactorAngle( int aMode )
{
  float l_PowerFactorAngle = acos( computePowerFactor() );

if( aMode == PS_DEGREES )
    l_PowerFactorAngle *= 180 / PI;

return( l_PowerFactorAngle );
}

float PowerSignal::computeReactivePower()
{
  return( computeApparentPower()  * sin( computePowerFactorAngle( PS_RADIANS ) ) );
}

void PowerSignal::reset()
{
  mSumVoltageTimesCurrent = 0;
}

void PowerSignal::updateAccumulator()
{
  mSumVoltageTimesCurrent += mVoltageSignal.getInstantaneousValue() * mCurrentSignal.getInstantaneousValue();
}

float PowerSignal::computeAveragePower()
{
  return( mSumVoltageTimesCurrent / mVoltageSignal.getSampleCount() );
}