/// <summary>
/// Calculates the Decay Time related values
/// </summary>
private void CalculateDecayTime()
{
// The percentage of the Peak Current to be the end of the decay time (1/e)
double decayTimeEndPercentOfIps = 1.0 / System.Math.E;
// Trim the waveform, removing everything before the max peak
Waveform absoluteWaveformAfterPeakCurrentTime = this.AbsoluteWaveform.TrimStart(this.PeakCurrentDataPoint.X);
// Find the start/stop times for the noise-reducing exponential fit waveform
DataPoint?expFitStartDataPoint = absoluteWaveformAfterPeakCurrentTime.DataPointAtYThreshold(0.5 * System.Math.Abs(this.PeakCurrentValue), true);
if (expFitStartDataPoint.HasValue)
{
double expFitStartTimeThreshold = expFitStartDataPoint.Value.X;
DataPoint?expFitEndDataPoint = absoluteWaveformAfterPeakCurrentTime.DataPointAtYThreshold(0.3 * System.Math.Abs(this.PeakCurrentValue), true);
// The waveform was truncated before the lower end of the decaying region,
// however there might be enough data to calculate by using the last data point instead.
if (!expFitEndDataPoint.HasValue)
{
expFitEndDataPoint = absoluteWaveformAfterPeakCurrentTime.DataPoints.Last();
}
double expFitEndTimeThreshold = expFitEndDataPoint.Value.X;
// Gate the waveform to just the area for the noise-reducing exponential fit waveform
Waveform absoluteWaveformDecayingRegion = this.AbsoluteWaveform.Gates(expFitStartTimeThreshold, expFitEndTimeThreshold);
if (absoluteWaveformDecayingRegion.DataPoints.Any())
{
// Find the exponential fit constants of the waveform from 0.5 * Ips to 0.3 * Ips to eliminate noise
Tuple <double, double> expFitAbsoluteWaveformDecayingRegionConstants = absoluteWaveformDecayingRegion.ExponentialFit();
// Create time values that go out far enough to ensure the decay time end threshold can be found
List <double> timeValues = (from dp in absoluteWaveformDecayingRegion.DataPoints select dp.X).ToList();
double samplingTime = absoluteWaveformDecayingRegion.SamplingTime();
while (timeValues.Last() < 0.000000800 && samplingTime > 0)
{
timeValues.Add(timeValues.Last() + samplingTime);
}
// Create the exponential fit equivalent waveform which has noise eliminated
Waveform expFitAbsoluteWaveformDecayingRegion = WaveformExtensions.CreateExponentialFitWaveform(
expFitAbsoluteWaveformDecayingRegionConstants.Item1,
expFitAbsoluteWaveformDecayingRegionConstants.Item2,
timeValues);
// Calculate what the decay time end threshold is (1/e % of Ips)
double decayTimeEndThreshold = System.Math.Abs(this.PeakCurrentValue) * decayTimeEndPercentOfIps;
// Find the first (interpolated) data point that is at 1/e % of Ips value (of the absolute value waveform)
DataPoint?decayTimeEndDataPointAbsolute = expFitAbsoluteWaveformDecayingRegion.DataPointAtYThreshold(decayTimeEndThreshold, true);
if (decayTimeEndDataPointAbsolute.HasValue)
{
// Convert the Decay Time end DataPoint to the signed value
this.DecayTimeEndDataPoint = decayTimeEndDataPointAbsolute.Value.InvertYValueIfNegativePolarity(this.WaveformIsPositivePolarity);
// Calculate the Decay Time
this.DecayTimeValue = this.DecayTimeEndDataPoint.X - this.PeakCurrentDataPoint.X;
// Determine if the Decay Time is passing
this.DecayTimeIsPassing = DoubleRangeExtensions.BetweenInclusive(this.DecayTimeAllowedMinimum, this.DecayTimeAllowedMaximum, this.DecayTimeValue);
}
else
{
// The derived exponential fit waveform didn't go out to a far enough time to capture the 1/e time.
}
}
else
{
// Could not find any data points in the decay time window. Likely due to a malformed waveform.
}
}
else
{
// Since the waveform was truncated before even the start of the window to calculate the decaying region, the decay time cannot be calculated.
}
}