Temperature (and humidity) measurement: Difference between revisions

Temperature (and humidity) measurement (view source)

Revision as of 08:19, 14 June 2020

1,689 bytes removed , 08:19, 14 June 2020

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→‎Cumulus Calculated Parameters

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 ==Cumulus Calculated Parameters==
 See external Wiki or other sections of this Wiki for specific information on the values that Cumulus calculates:
@@ Line 89: / Line 90: @@
 *The dew point calculation for Cumulus 1 uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)'''
-* The dew point calculation for MX follows the standard [https://en.wikipedia.org/wiki/Dew_point calculation in wikipedia].
+* The dew point calculation for MX follows the standard [https://en.wikipedia.org/wiki/Dew_point calculation in wikipedia]
+<pre>public static double DewPoint(double tempC, double humidity)
+        {
+            //return tempC + ((0.13*tempC) + 13.6)*Math.Log(humidity/100.0);
+            // Davis algorithm
+            double lnVapor = Math.Log(ActualVapourPressure(tempC, (int) humidity));
+            return ((243.12 * lnVapor) - 440.1) / (19.43 - lnVapor);
+        }</pre>
 Note this means that Cumulus 1 and MX log files have a continuity break when you migrate from one flavour to another.
-<pre>
-	/* =================================================================================================
-	 DEW POINT TEMPERATURE
-	The dew point calculation in Cumulus 1 uses a third party library which uses the Davis dew point calculation '''dewpoint := tempinC + ((0.13 * tempinC) + 13.6) * Ln(humidity / 100)'''
-	============================================================================== */
-	function calcDewPoint(tempDegC,	 tempLetter,	 RHumidity)
-	{
-		var dp = tempDegC + ((0.13 * tempDegC) +13.6) * Math.log(RHumidity / 100);
-		return  calcTempR(dp,	tempLetter);   // return as string in right units for user
-	}
-	/* =================================================================================================
-	 DEW POINT TEMPERATURE
-	 The following is a formula from  https://github.com/nicolasgrancher/weather-js/blob/master/js/weather.js
-	 This matches the formula that MX uses.
-	It has only been edited to add the middle input parameter and to output using a call to CalcTempR
-	============================================================================== */
-/**
- * Dew point calculation.
- * @see https://en.wikipedia.org/wiki/Dew_point
- *
- * @param Tc temperature in celsius
- * @param R relative humidity
- * @returns {number}
- */
-function dewPoint(Tc,	tempLetter,  R)
- {  // parameters:		tempDegC, tempLetter, (RHumidity /100)  // added middle parameter, should be accessible anyway, but playing safe
-    if (Tc < 0 || Tc > 60)
-	{
-        return  calcTempR(Tc,	tempLetter);   // return as string in right units for user
-    }
-    if (R < 0.01 || R > 1) {
-        return  calcTempR(Tc,	tempLetter);   // return as string in right units for user
-    }
-    var a = 17.27;
-    var b = 237.7;
-    var alphaTR = ((a * Tc) / (b + Tc)) + Math.log(R);
-    var Tr = (b * alphaTR) / (a - alphaTR);
-    if (Tr < 0 || Tr > 50) {
-        return  calcTempR(Tc,	tempLetter);   // return as string in right units for user
-    }
-        return  calcTempR(Tr,	tempLetter);   // return as string in right units for user
-}
-</pre>