Measure the air temperature and relative humidity
Use the Magnus formula:
( gamma = ln(text{RH}/100) + frac{aT}{b+T} )
( T_d = frac{bgamma}{a-gamma} )
Use constants:
( a = 17.27 )
( b = 237.7^circ C )
Substitute:
( T ) = air temperature in °C
RH = relative humidity in %
Calculate ( gamma )
Calculate dew point temperature ( T_d )
Convert units if needed:
( T_d(^circ F) = T_d(^circ C)times frac{9}{5} + 32 )