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Temperature (and humidity) measurement: Difference between revisions
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Temperature (and humidity) measurement (view source)
Revision as of 19:49, 31 July 2021
, 19:49, 31 July 2021→How Cumulus software handles Temperature and Humidity
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=How Cumulus software handles Temperature and Humidity= | =How Cumulus software handles Temperature and Humidity= | ||
Cumulus expects all stations to report a minimum number of parameters including outside temperature and relative humidity. Some weather station types also report wind chill, dew-point temperature, and other derivatives related to temperature and/or relative humidity. Cumulus is able to calculate wind chill, dew-point, and other derivatives (and if any of these are available from your station, you can choose whether to use the value from station or the value Cumulus calculates). | |||
If Cumulus (1 or MX) is using "outside temperature" in a calculation of parameters like dew-point, or apparent temperature, then for most stations it will apply any calibration settings to the temperature read from the station before using it in that calculation. In Cumulus 1, uncalibrated temperature values are used from Instromet, see support forum for more details. | |||
Similarly if humidity is read from the station, the calibrated value is used in subsequent calculations. See the support forum for further information e.g. '''for Instromet stations''', Cumulus 1 ''calculates the relative humidity from the reported wet bulb, and dry bulb'', temperatures, the uncalibrated values of temperature and (calculated) humidity are then used to calculate dew-point. | |||
== Logged values == | == Logged values == | ||
At the logging interval you set, Cumulus logs outdoor temperature, dew-point, and relative humidity; plus a whole host of values derived from them (and from wind speed), in [[Standard_log_files]], with separate files for each month. | At the logging interval you set, Cumulus logs outdoor temperature, dew-point, and relative humidity; plus a whole host of values derived from them (and from wind speed), in [[Standard_log_files]], with separate files for each month. | ||
Optionally, measurements from extra sensors can be logged in [[Extra_Sensor_Files| extra monthly files]]. | Optionally, measurements from extra sensors can be logged in [[Extra_Sensor_Files| extra monthly files]]. For Oregon Scientific stations, temperature readings from one extra sensor can optionally replace the main sensor for "outdoor temperature", see [[Webtags#Web_tags_mentioning_.28outside.29_temperature|here]]for details. | ||
Optionally, but only in Cumulus 1, indoor measurements can be logged in [[speciallog.txt|a special ongoing log]]. | Optionally, but only in Cumulus 1, indoor measurements can be logged in [[speciallog.txt|a special ongoing log]]. | ||
From release 3.12.0, MX maintains a [[Cumulusmx.db|database table]] that can hold temperatures at one (assuming MX has been left running) minute intervals for the last 7 days. | |||
==Cumulus Calculated Parameters== | ==Cumulus Calculated Parameters== | ||
See external Wiki or other sections of this Wiki for specific information on the values that Cumulus calculates: | See external Wiki or other sections of this Wiki for specific information on the values that Cumulus calculates: | ||
[http://en.wikipedia.org/wiki/Wet_bulb Wet bulb] | [http://en.wikipedia.org/wiki/Wet_bulb Wet bulb] | ||
and [[#How_does_Cumulus_know_the_height_of_the_cloud_base.3F]] | |||
The dew point calculation 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 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] | |||
<pre>public static double DewPoint(double tempC, double humidity) | |||
{ | |||
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 in dew point values when you migrate from one flavour to another. | |||
Look up [[Humidex]], [[Wind chill]], [[Heat index]], [[Apparent temperature]], [[Feels Like|Feels Like temperature]], [[Heat/cold degree days and Chill hours]], [[Average temperature]], | |||
[[Extra_Sensor_Files|Extra temperatures]] for details about the various derivatives. | |||
[[Category:Terminology]] | [[Category:Terminology]] | ||
History: | |||
[[User:Sfws|Sfws]] 00:34, 29 November 2012 (UTC) | * Created: [[User:Sfws|Sfws]] 00:34, 29 November 2012 (UTC) for legacy Cumulus | ||
* Amended: [[User:Sfws|Sfws]] ([[User talk:Sfws|talk]]) 19:49, 31 July 2021 (UTC) to also cover MX as at 3.12.0 | |||
