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Added dew point, updated example #12

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Aug 13, 2018
Merged

Added dew point, updated example #12

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12a7d6e
Added dew point, updated example
kattni Aug 13, 2018
cdd59a1
Linting.
kattni Aug 13, 2018
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12 changes: 12 additions & 0 deletions adafruit_bme280.py
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,18 @@ def _read_temperature(self):
self._t_fine = int(var1 + var2)
#print("t_fine: ", self.t_fine)

@property
def dew_point(self):
# pylint: disable=invalid-name
# Disable: c is a constant used in the Magnus formula
"""The dew point in Celsius using the Magnus formula. Constants from Sontag, 1990."""
b = 17.62
c = 243.12
gamma = (b * self.temperature /(c + self.temperature)) + math.log(self.humidity / 100.0)
dewpoint = (c * gamma) / (b - gamma)
return dewpoint
# pylint: enable=invalid-name

@property
def temperature(self):
"""The compensated temperature in degrees celsius."""
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7 changes: 4 additions & 3 deletions examples/bme280_simpletest.py
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Expand Up @@ -9,9 +9,9 @@
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

# OR create library object using our Bus SPI port
#spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
#bme_cs = digitalio.DigitalInOut(board.D10)
#bme280 = adafruit_bme280.Adafruit_BME280_SPI(spi, bme_cs)
# spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
# bme_cs = digitalio.DigitalInOut(board.D5)
# bme280 = adafruit_bme280.Adafruit_BME280_SPI(spi, bme_cs)

# change this to match the location's pressure (hPa) at sea level
bme280.sea_level_pressure = 1013.25
Expand All @@ -21,4 +21,5 @@
print("Humidity: %0.1f %%" % bme280.humidity)
print("Pressure: %0.1f hPa" % bme280.pressure)
print("Altitude = %0.2f meters" % bme280.altitude)
print("Dew point = %0.1f C" % bme280.dew_point)
time.sleep(2)