absolute pressure + relative pressure(F) to inHg automatically

MeteoFunctions.cpp

@@ -97,7 +97,7 @@ float MeteoFunctions::ft_m(float feet) {
  * Converts hPa to inHg
  */
 float MeteoFunctions::hPa_inHg(float hPa) {
-    return 0.02952998751 * hPa;
+    return hPa * 0.02952998751;
 }
 
 /**
@@ -107,6 +107,20 @@ float MeteoFunctions::inHg_hPa(float inHg) {
     return inHg / 0.02952998751;
 }
 
+/**
+ * Converts g/m3 to gr/ft3
+ */
+float MeteoFunctions::gm3_grft3(float gm3) {
+    return gm3 * 0.0283168466;
+}
+
+/**
+ * Converts gr/ft3 to g/m3
+ */
+float MeteoFunctions::grft3_gm3(float grft3) {
+    return grft3 / 0.0283168466;
+}
+
 /**
  * Calculates humidex in Celsius
  */
@@ -268,5 +282,25 @@ float MeteoFunctions::relativePressure_c(float abs_pressure, float height_m, flo
  * Calculates relative pressure
  */
 float MeteoFunctions::relativePressure_f(float abs_pressure, float height_ft, float temp_f) {
-    return relativePressure_c(abs_pressure, ft_m(height_ft), f_c(temp_f));
+    return hPa_inHg(relativePressure_c(abs_pressure, ft_m(height_ft), f_c(temp_f)));
 }
+
+/**
+ * Calculates absolute humidity
+ */
+float MeteoFunctions::absoluteHumidity_c(float temp_c, float humidity) {
+    double abs = 6.112 * exp(17.67 * temp_c / (temp_c + 243.5));
+    abs *= humidity * 2.1674;
+    abs /= (273.15 + temp_c);
+
+    return static_cast<float>(abs);
+}
+
+/**
+ * Calculates absolute humidity
+ */
+float MeteoFunctions::absoluteHumidity_f(float temp_f, float humidity) {
+    return gm3_grft3(absoluteHumidity_c(f_c(temp_f), humidity));
+}
+
+

MeteoFunctions.h

@@ -1,6 +1,6 @@
 /*
 MIT License
-Copyright (c) 2018 Pavel Slama
+Copyright (c) 2019 Pavel Slama
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
@@ -42,6 +42,8 @@ class MeteoFunctions {
   float   knToMs(float kn);
   float   m_ft(float meters);
   float   ft_m(float feet);
+  float   gm3_grft3(float gm3);
+  float   grft3_gm3(float grft3);
   float   hPa_inHg(float hPa);
   float   inHg_hPa(float inHg);
   float   humidex_c(float temp_c, float humidity);
@@ -59,6 +61,8 @@ class MeteoFunctions {
   float   cloudBase_f(float temp_f, float humidity);
   float   relativePressure_c(float abs_pressure, float height_m, float temp_c);
   float   relativePressure_f(float abs_pressure, float height_ft, float temp_f);
+  float   absoluteHumidity_c(float temp_c, float humidity);
+  float   absoluteHumidity_f(float temp_f, float humidity);
 };
 
 #endif  // METEOFUNCTIONS_H

README.md

@@ -12,8 +12,9 @@ Do you have your own meteo station based on Arduino or Mbed? and ever wondered h
 - Apparent temperature
 - Cloud height base
 - Relative pressure
+- Absolute humidity
 
-Let's add them to your project. You don't need any special sensors, it's just a math. Here is a class that do that for you. Supports both **Celsius** and **Fahrenheit**.
+Let's add them to your project. You don't need any special sensors, it's just a math. Here is a class that do that for you. Supports both **Celsius** and **Fahrenheit**, please navigate to full example.
 
 ## Example
 ```cpp
@@ -67,7 +68,10 @@ void loop() {
 
     Serial.print(" metres\n: ");
     Serial.print(calc.relativePressure_c(pressure, above_sea, temp));
-    Serial.println(" Pa");
+
+    Serial.print(" Pa\nAbsolute humidity: ");
+    Serial.print(calc.absoluteHumidity_c(temp, humidity));
+    Serial.println(" g/m3\n");
 
     delay(5000);
 }

examples/MeteoFunctions/MeteoFunctions.ino

@@ -61,7 +61,10 @@ void loop() {
 
     Serial.print(" metres\nRelative pressure: ");
     Serial.print(calc.relativePressure_c(pressure, above_sea, temp));
-    Serial.println(" Pa\n");
+
+    Serial.print(" Pa\nAbsolute humidity: ");
+    Serial.print(calc.absoluteHumidity_c(temp, humidity));
+    Serial.println(" g/m3\n");
 
 #elif defined(FAHRENHEIT)
     Serial.print("Wind speed: ");
@@ -98,8 +101,11 @@ void loop() {
     Serial.print(calc.cloudBase_f(temp, humidity));
 
     Serial.print(" feet\nRelative pressure: ");
-    Serial.print(calc.hPa_inHg(calc.relativePressure_f(pressure, above_sea, temp)));
-    Serial.println(" inHg\n");
+    Serial.print(calc.relativePressure_f(pressure, above_sea, temp));
+
+    Serial.print(" inHg\nAbsolute humidity: ");
+    Serial.print(calc.absoluteHumidity_f(temp, humidity));
+    Serial.println(" gr/ft3\n");
 #endif
     delay(5000);
 }

keywords.txt

@@ -6,6 +6,8 @@ msToMph	KEYWORD2
 msToKn	KEYWORD2
 m_f	KEYWORD2
 f_m	KEYWORD2
+gm3_grft3 KEYWORD2
+grft3_gm3 KEYWORD2
 humidex_c	KEYWORD2
 humidex_f	KEYWORD2
 dewPoint_c	KEYWORD2
@@ -21,3 +23,5 @@ cloudBase_m	KEYWORD2
 cloudBase_f	KEYWORD2
 relativePressure_c	KEYWORD2
 relativePressure_f	KEYWORD2
+absoluteHumidity_c  KEYWORD2
+absoluteHumidity_f  KEYWORD2

library.json

@@ -13,7 +13,7 @@
       "email": "info@pavelslama.cz",
       "url": "https://github.com/pilotak"
   },
-  "version": "1.0.4",
+  "version": "1.1.0",
   "frameworks": "arduino, mbed",
   "platforms": "*"
 }

library.properties

@@ -7,5 +7,5 @@ paragraph=extend your meteo station by calculating other meteorologist values
 url=https://github.com/pilotak/MeteoFunctions
 includes=MeteoFunctions.h
 category=Data Processing
-version=1.0.4
+version=1.1.0
 architectures=*