public void Measure(int wavelengths, int timeout)
{
int crossCount = 0; //Used to measure number of times threshold is crossed.
int numberOfSamples = 0; //This is now incremented
//-------------------------------------------------------------------------------------------------------------------------
// 1) Waits for the waveform to be close to 'zero' (500 adc) part in sin curve.
//-------------------------------------------------------------------------------------------------------------------------
bool st = false; //an indicator to exit the while loop
while (st == false && crossCount < 1000) //the while loop...
{
startVoltage = AnalogRead(voltageInput); //using the voltage waveform
if ((startVoltage < 550) && (startVoltage > 440))
{
st = true; //check its within range
}
crossCount++;
}
if (crossCount >= 1000)
{
Debug.Print("ERROR:Could not detect zero signal level. Last value=" + startVoltage.ToString());
return;
}
crossCount = 0;
//-------------------------------------------------------------------------------------------------------------------------
// 2) Main measurment loop
//-------------------------------------------------------------------------------------------------------------------------
int start = DateTime.Now.Millisecond; //millis()-start makes sure it doesnt get stuck in the loop if there is an error.
while ((crossCount < wavelengths) && ((DateTime.Now.Millisecond - start) < timeout))
{
numberOfSamples++; //Count number of times looped.
lastSampleVoltage = sampleVoltage; //Used for digital high pass filter
lastSampleCurrent = sampleCurrent; //Used for digital high pass filter
lastFilteredVoltage = filteredVoltage; //Used for offset removal
lastFilteredCurrent = filteredCurrent; //Used for offset removal
// A) Read in raw voltage and current samples
sampleVoltage = AnalogRead(voltageInput); //Read in raw voltage signal
sampleCurrent = AnalogRead(currentInput); //Read in raw current signal
// B) Apply digital high pass filters to remove 2.5V DC offset (centered on 0V).
filteredVoltage = 0.996 * (lastFilteredVoltage + sampleVoltage - lastSampleVoltage);
filteredCurrent = 0.996 * (lastFilteredCurrent + sampleCurrent - lastSampleCurrent);
// C) Root-mean-square method voltage
squaredVoltage = filteredVoltage * filteredVoltage; //1) square voltage values
voltageSum += squaredVoltage; //2) sum
// D) Root-mean-square method current
squaredCurrent = filteredCurrent * filteredCurrent; //1) square current values
currentSum += squaredCurrent; //2) sum
// E) Phase calibration
phaseShiftedVoltage = lastFilteredVoltage + calibrationPhase * (filteredVoltage - lastFilteredVoltage);
// F) Instantaneous power calc
instantaneousPower = phaseShiftedVoltage * filteredCurrent; //Instantaneous Power
powerSum += instantaneousPower; //Sum
// G) Find the number of times the voltage has crossed the initial voltage
// - every 2 crosses we will have sampled 1 wavelength
// - so this method allows us to sample an integer number of wavelengths which increases accuracy
lastVoltageCross = checkVoltageCross;
if (sampleVoltage > startVoltage)
{
checkVoltageCross = true;
}
else
{
checkVoltageCross = false;
}
if (numberOfSamples == 1)
{
lastVoltageCross = checkVoltageCross;
}
if (lastVoltageCross != checkVoltageCross)
{
crossCount++;
}
}
// 3) Post loop calculations
//Calculation of the root of the mean of the voltage and current squared (rms)
//Calibration coeficients applied.
RMSVoltage = calibrationVoltage * SquaredRoot(voltageSum / numberOfSamples);
RMSCurrent = calibrationCurrent * SquaredRoot(currentSum / numberOfSamples);
//Calculation power values
RealPower = calibrationVoltage * calibrationCurrent * powerSum / numberOfSamples;
ApparentPower = RMSVoltage * RMSCurrent;
PowerFactor = RealPower / ApparentPower;
// kwh increment calculation
// 1) find out how much time there has been since the last measurement of power
lwhtime = whtime;
whtime = DateTime.Now.Ticks;
whInc = RealPower * ((whtime - lwhtime) / 3600000.0);
//Reset accumulators
voltageSum = 0;
currentSum = 0;
powerSum = 0;
//--------------------------------------------------------------------------------------
Debug.Print("rmsVoltage = " + RMSVoltage.ToString() + " rmsCurrent = " + RMSCurrent.ToString() + " apparentPower = " + ApparentPower.ToString() + " PowerFactor = " + PowerFactor.ToString() + " Wh = " + whInc.ToString());
}
