SHTxx

Humidity & Temperature Sensmitter

Application Note Relative Humidity Calculation

Calculation of relative humidity at a given temperature

RH

1

, T

1

, D

1

RH

2

, T

2

, D

2

A

Figure 1: Chamber

A

with constant dew-point

D1=D2

. It is assumed that the dew-point in chamber

A

is constant, i.e.

D

1

=D

2 . Given the relative humidity

RH

1 at temperature

T

1 in chamber

A

, the relative humidity

RH

2 at temperature

T

2 can be calculated using
n

12

(1)

with parameters

eeRHRH

TTnmTTTmT

2211 .For calculations with micro-controllers, formula (1) can be expressed as
RH2 = RH1 * 10^( 7.6523 * T1 / ( 243.12 + T1 )) / 10^( 7.6523 * T2 / ( 243.12 + T2 )) For further information please refer to the Application note “Dew point calculation”.
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