humidity.py

   1 #!/usr/bin/env python
   2 # -*- coding: iso-8859-15 -*-
   3
   4 RS = 8314.3 # J/(kmol*K) universelle Gaskonstante
   5 MW = 18.016 # kg/kmol Molekulargewicht des Wasserdampfes
   6
   7 # Openweathermap
   8 STATION=2911298
   9 API_ID="41ff32c10636d35b4c7a46000cb1a6a1"
  10
  11 import urllib
  12 import json
  13
  14 # Sättigungsdampfdruck in hPa
  15 def calc_saturation_vapor_pressure(temp_c):
  16         if temp_c >= 0:
  17                 a = 7.5
  18                 b = 237.3
  19         else:
  20                 a = 7.6
  21                 b = 240.7
  22
  23         return 6.1078 * 10**((a*temp_c)/(b+temp_c))
  24
  25
  26 # https://www.wetterochs.de/wetter/feuchte.html
  27 def calc_humidity_abs(temp_c, humdity_rel):
  28         temp_k = temp_c + 273.15
  29
  30         # Dampfdruck in hPa
  31         SDD = calc_saturation_vapor_pressure(temp_c)
  32         DD = humdity_rel/100.0 * SDD
  33         humidity_abs = 10**5 * MW/RS * DD/temp_k
  34         return humidity_abs
  35
  36
  37 def calc_humidity_rel(temp_c, humidity_abs):
  38         temp_k = temp_c + 273.15
  39         SDD = calc_saturation_vapor_pressure(temp_c)
  40         DD = humidity_abs*temp_k * RS / (10**5*MW)
  41
  42         humdity_rel = DD/SDD*100
  43         return humdity_rel
  44
  45 def get_weather_current():
  46         query = urllib.urlencode({'id': STATION, 'APPID': API_ID, 'lang': 'de'})
  47         url = "http://api.openweathermap.org/data/2.5/weather?units=metric&%s" % query
  48         response = urllib.urlopen(url)
  49         results = response.read()
  50         return json.loads(results)
  51
  52 def check_ventilate(temp_indoor, humdity_rel_indoor):
  53         dWeatherCurrent = get_weather_current()
  54         temp_outdoor = dWeatherCurrent["main"]["temp"]
  55         humdity_rel_outdoor = dWeatherCurrent["main"]["humidity"]
  56
  57         humdity_abs_indoor = calc_humidity_abs(temp_indoor, humdity_rel_indoor)
  58         humdity_abs_outdoor = calc_humidity_abs(temp_outdoor, humdity_rel_outdoor)
  59
  60         print "Wassergehalt Innen: %.2f, Außen: %.2f" % (humdity_abs_indoor, humdity_abs_outdoor)
  61         return humdity_abs_indoor/humdity_abs_outdoor
  62
  63
  64 if __name__ == "__main__":
  65         check_ventilate(21, 50)