private double CalculateStrain(StrainConfig StrainCfg, double U, double GageFactor, double PoissonRatio)
{
double starin = 0;
switch (StrainCfg)
{
case StrainConfig.FullBridgeI:
starin = (-U) / GageFactor;
break;
case StrainConfig.FullBridgeII:
starin = (-2 * U) / (GageFactor * (1 + PoissonRatio));
break;
case StrainConfig.FullBridgeIII:
starin = (-2 * U) / (GageFactor * ((PoissonRatio + 1) - (U * (PoissonRatio - 1))));
break;
case StrainConfig.HalfBridgeI:
starin = (-4 * U) / (GageFactor * ((PoissonRatio + 1) - 2 * U * (PoissonRatio - 1)));
break;
case StrainConfig.HalfBridgeII:
starin = (-2 * U) / GageFactor;
break;
case StrainConfig.QuarterBridgeI:
case StrainConfig.QuarterBridgeII:
starin = (-4 * U) / (GageFactor * ((1 + 2 * U)));
break;
}
return(starin);
}
private void cmdStart_Click(object eventSender, System.EventArgs eventArgs)
{
int i;
MccDaq.ErrorInfo ULStat;
MccDaq.Range Range;
MccDaq.ScanOptions Options;
int Rate;
int Count;
int Chan;
StrainConfig StrainConfiguration = StrainConfig.QuarterBridgeI;
double InitialVoltage = 0.0; //Bridge output voltage in the unloaded condition. This value is subtracted from any measurements before scaling equations are applied.
double VInitial = 0.0;
double OffsetAdjustmentFactor = 0.0;
double GainAdjustmentFactor = 0.0;
double Total = 0.0;
double VOffset = 0.0;
double RShunt = 100000; // Resistance of Shunt Resistor
double RGage = 350; // Gage Resistance
double VExcitation = 2.5; // Excitation voltage
double GageFactor = 2;
double PoissonRatio = 0;
double VActualBridge; // Actual bridge voltage
double REffective; // Effective resistance
double VSimulatedBridge; // Simulated bridge voltage
double MeasuredStrain;
double SimulatedStrain;
cmdStart.Enabled = false;
// Calculate the offset adjusment factor on a resting gage in software
// Collect the values by calling MccDaq.MccBoard.AInScan function
// Parameters:
// LowChan :the first channel of the scan
// HighChan :the last channel of the scan
// Count :the total number of A/D samples to collect
// Rate :sample rate
// Range :the range for the board
// MemHandle :Handle for Windows buffer to store data in
// Options :data collection options
Chan = int.Parse(txtChan.Text); // channel to acquire
if ((Chan > 3))
{
Chan = 3;
}
txtChan.Text = Chan.ToString();
VInitial = InitialVoltage / VExcitation;
Count = NumPoints; // total number of data points to collect
Rate = 1000; // per channel sampling rate ((samples per second) per channel)
// return scaled data
Options = MccDaq.ScanOptions.ScaleData;
Range = MccDaq.Range.NotUsed; // set the range
ULStat = DaqBoard.AInScan(Chan, Chan, Count, ref Rate, Range, MemHandle, Options);
// Transfer the data from the memory buffer set up by Windows to an array
ULStat = MccDaq.MccService.ScaledWinBufToArray(MemHandle, ADData, FirstPoint, Count);
for (i = 0; i < NumPoints; i++)
{
Total = Total + ADData [i];
}
VOffset = Total / Count;
VOffset = VOffset - VInitial;
OffsetAdjustmentFactor = CalculateStrain(StrainConfiguration, VOffset, GageFactor, PoissonRatio);
lblOffsetMeasStrain.Text = OffsetAdjustmentFactor.ToString("F9");
// Enable Shunt Calibration Circuit and Collect the values and
// Calculate the Actual Bridge Voltage
Options = MccDaq.ScanOptions.ScaleData | MccDaq.ScanOptions.ShuntCal;
ULStat = DaqBoard.AInScan(Chan, Chan, Count, ref Rate, Range, MemHandle, Options);
// Transfer the data from the memory buffer set up by Windows to an array
ULStat = MccDaq.MccService.ScaledWinBufToArray(MemHandle, ADData, FirstPoint, Count);
Total = 0.0;
for (i = 0; i < Count; i++)
{
Total = Total + ADData [i];
}
VActualBridge = Total / Count;
VActualBridge = VActualBridge - VInitial;
MeasuredStrain = CalculateStrain(StrainConfiguration, VActualBridge, GageFactor, PoissonRatio);
lblGainMeasStrain.Text = MeasuredStrain.ToString("F9");
// Calculate the Simulated Bridge Strain with a shunt resistor
REffective = (RGage * RShunt) / (RGage + RShunt);
VSimulatedBridge = (REffective / (REffective + RGage) - 0.5);
SimulatedStrain = CalculateStrain(StrainConfiguration, VSimulatedBridge, GageFactor, PoissonRatio);
lblGainSimStrain.Text = SimulatedStrain.ToString("F9");
GainAdjustmentFactor = SimulatedStrain / (MeasuredStrain - OffsetAdjustmentFactor);
lblGainAdjustmentFactor.Text = GainAdjustmentFactor.ToString("F9");
cmdStart.Enabled = true;
}
