General

This is an amateur weather station mounted on a balcony.
The weather station works on a Raspberry Pi Zero W microcomputer.

Available readings

Air temperature

A DS18B20 sensor was used to measure the temperature.
The temperature is given to one decimal place.
The unit of temperature is degrees celsius [°C].

Relative humidity

A BME280 sensor was used to measure humidity.
Humidity is given as an integer.
The unit of humidity is percent [%].

Atmospheric pressure

A BME280 sensor was used to measure the pressure.
The pressure is given as an integer.
The unit of pressure is the hectopascal [hPa].

Dew point temperature

The dew point is calculated from the formula:

$$ t_d = \sqrt[8]{ \frac{H}{100} } \cdot [112 + (0.9 \cdot t)] + (0.1 \cdot t) - 112 $$

where:

$t_d$ – dew point temperature [°C]
$t$ – temperature [°C]
$H$ – relative humidity [%]

Source of formula: Wikipedia

The dew point is given to one decimal place.
The unit of dew point is degrees celsius [°C].

Particulate matter

PM 1.0 (up to 1 μm diameter), PM 2.5 (up to 2.5 μm diameter) and PM 10 (up to 10 μm diameter) are measured.
The PMS5003 sensor was used to measure particulate matter.
Particulate matter is given as an integer.
The unit of particulate matter is micrograms per cubic meter [ $\frac{μg}{m^3}$ ].

Air Quality Index (AQI)

The standard for PM 10 is 180 $\frac{μg}{m^3}$ and for PM 2.5 is 110 $\frac{μg}{m^3}$.

The air quality index is calculated from the formula:

$$ AQI = \frac{ \frac{ PM_{10} }{ 1.8 } + \frac{ PM_{2.5} }{ 1.1 } }{ 2 } $$

where:

$AQI$ - Air quality index
$PM_{10}$ - PM 10 particulate matter
$PM_{2.5}$ - PM 2.5 particulate matter

The index has five levels:

Index	Compartment
Very good	$\langle 0, 25 \rangle$
Good	$( 25, 50 \rangle$
Medium	$( 50, 75 \rangle$
Bad	$( 75, 100 \rangle$
Very bad	$( 100, \infty )$

The index is given as an integer.
The unit of AQI is percent [%].

Archive readings

Archive readings are given every hour.
Their value is the average of readings saved every 10 minutes.