22

Author: BasicAirData

Software/Arduino/Libraries/AirDC/AirDC.cpp

@@ -151,13 +151,26 @@ void AirDC::IAS(int mode)
         break;
     }
 }
+void AirDC::CAS(int mode)
+{
+//Calibrated Airspeed
+    //http://www.basicairdata.eu/pitot-tube.html
+    //https://en.wikipedia.org/wiki/Equivalent_airspeed
+    switch (mode)
+    {
+    case 1:
+    _CAS=_IAS;
+    _uCAS=_uIAS;
+        break;
+    }
+}
 void AirDC::TAS(int mode)
 {
 //True Airspeed
 //http://www.basicairdata.eu/pitot-tube.html
 //TAS=IAS*(rhostandard/rhoair)^0.5
-    _TAS=_IAS*sqrt(1.225/_Rho);
-    _uTAS= sqrt((1.225/_Rho)*pow(_uIAS,2)+ pow(0.5*_IAS*1.225/(pow(_Rho,1.5)),2)*pow(_uRho,2));
+    _TAS=_CAS*sqrt(1.225/_Rho);
+    _uTAS= sqrt((1.225/_Rho)*pow(_uCAS,2)+ pow(0.5*_CAS*1.225/(pow(_Rho,1.5)),2)*pow(_uRho,2));
 }
 void AirDC::Mach(int mode)
 {
@@ -187,15 +200,32 @@ void AirDC::OAT(int mode)
 //https://en.wikipedia.org/wiki/Total_air_temperature
     switch (mode)
     {
-case 1:
+    case 1:
     {
         double gamma=1.4; //cp/cv
         //https://en.wikipedia.org/wiki/Julius_von_Mayer#Mayer.27s_relation
 
         _T=_TAT/(1+(gamma-1)/2*pow(_M,2));
         _uT=1/(1+(gamma-1)/2*2*pow(_M,2))*_uTAT;
     }
+    }
+
 }
+void AirDC::ISAAltitude(int mode)
+{
+    switch (mode)
+    {
+    case 1:
+    {
+        double Ps,h;
+        Ps=_p/133.3223684211/25.4;//Pa to inHg Conversion
+        //Using Goodrich 4081 Air data handbook formula
+        _h=(pow(29.92126,0.190255)-pow(Ps,0.190255))/0.000013125214; //US atmosphere 1962
+        //Back to SI
+        _h=h*0.3048;
+        _uh=0.057989724*pow(Ps,-0.809745)*258006317.725680592912*_up;
+    }
+    }
 
 }
 

Software/Arduino/Libraries/AirDC/AirDC.h

@@ -13,9 +13,11 @@ class AirDC
     AirDC(int pid);
     void RhoAir(int mode);
     void IAS(int mode);
+    void CAS(int mode);
     void TAS(int mode);
     void Mach(int mode);
     void OAT(int mode);
+    void ISAAltitude(int mode);
 //private:
     int _pid;
     double _p;
@@ -24,18 +26,22 @@ class AirDC
     double _qc;
     double _Rho;
     double _IAS;
+    double _CAS;
     double _TAS;
     double _M;
     double _TAT;
+    double _h;
 //uncertainty terms
     double _up;
     double _uT;
     double _uRH;
     double _uRho;
     double _uqc;
     double _uIAS;
+    double _uCAS;
     double _uTAS;
     double _uTAT;
+    double _uh;
 };
 #endif
 

Software/Arduino/Libraries/AirDC/Examples/DifferentialPressureSensor/DifferentialPressureSensor.ino

@@ -9,6 +9,7 @@
 
 #define DPSENSOR 3 //Selects the differential pressure Hardware sensor see AirSensor.cpp for details on Hookup
 #define PSENSOR 1 //Selects the static pressure Hardware sensor see AirSensor.cpp for details on Hookup
+#define DEBUG 1 //
 
 #if DPSENSOR==1
 #include <Wire.h>
@@ -53,11 +54,13 @@ void loop() {
   AirDataSensor.ReadTAT(ptrAirDC, psensor);
   AirDataSensor.ReadRH(ptrAirDC, psensor);
 //Computation
-  AirDataComputer.IAS(1);// Calculates the IAS, Algorithm 1
   AirDataComputer.RhoAir(1);// Calculates the air density, Algorithm 1
+  AirDataComputer.IAS(1);// Calculates the IAS, Algorithm 1
+  AirDataComputer.CAS(1);// Calculates the CAS, Algorithm 1
   AirDataComputer.TAS(1);// Calculates the IAS, Algorithm 1
   AirDataComputer.Mach(1);// Calculates the Mach number, Algorithm 1
   AirDataComputer.OAT(1);// Calculates the Outside Air Temperature, Algorithm 1
+  AirDataComputer.ISAAltitude(1);// Calculates the ISA altitude from static pressure, Algorithm 1
   delay(1000); //loop delay
 //Visualitation  
   Serial.println(dpsensor);  //Prints the Selected sensor
@@ -70,6 +73,8 @@ void loop() {
   Serial.println(AirDataComputer._uIAS, 10); //Sends the uncertainty of IAS measurement
   Serial.println(AirDataComputer._Rho,4);//Sends the density of Air
   Serial.println(AirDataComputer._uRho, 10); //Sends the uncertainty of the density of air
+  Serial.println(AirDataComputer._CAS); //Calibrated AirSpeed
+  Serial.println(AirDataComputer._uCAS); //Calibrated AirSpeed uncertainty
   Serial.println(AirDataComputer._TAS); //True Airspeed
   Serial.println(AirDataComputer._uTAS); //True Airspeed uncertainty
   Serial.println(AirDataComputer._M,10); //Mach number
@@ -79,4 +84,6 @@ void loop() {
   Serial.println(AirDataComputer._uT); //Outside Temperature, Static Temperature uncertainty
   Serial.println(AirDataComputer._RH); //Relative Humidity
   Serial.println(AirDataComputer._uRH); //Relative Humidity Uncertainty
+  Serial.println(AirDataComputer._h); //Altitude
+  Serial.println(AirDataComputer._uh); //Altitude Uncertainty
 }

Software/Arduino/Libraries/AirDC/keywords.txt

@@ -1,4 +1,8 @@
 AirDC	KEYWORD1
 RhoAir	KEYWORD2
 IAS	KEYWORD2
-TAS	KEYWORD2
+CAS	KEYWORD2
+TAS	KEYWORD2
+Mach	KEYWORD2
+OAT	KEYWORD2
+ISAAltitude	KEYWORD2

Software/Arduino/Libraries/AirSensor/AirSensor.cpp

@@ -105,7 +105,9 @@ void AirSensor::ReadDifferentialPressure(AirDC *out,int sensor)
         raw = analogRead(analogPin);
         Vread=5.0/1023.0*(raw);
         Pread=(Vread-2.5-offsetv)*1000;
+        #if DEBUG==1
         Pread=1000;
+        #endif
         out->_qc=Pread; //pa
         out->_uqc=50.0;//pa
     }