# Commission Delegated Regulation (EU) 2017/654 of 19 December 2016 supplementing Regulation (EU) 2016/1628 of the European Parliament and of the Council with regard to technical and general requirements relating to emission limits and type-approval for internal combustion engines for non-road mobile machinery, Division 3.3.2.4: Dew point determination from relative humidity and dry bulb temperature

Extent: E+W+S+N.I.

If humidity is measured as a relative humidity, RH %, the dew point, T dew, shall be determined from RH % and dry bulb temperature by means of equation (7-81):
T dew = 2,0798233 × 10 2 − 2,0156028 × 10 1 × ln p H2O + 4,6778925 × 10 – 1 × ln p H2O 2 − 9,2288067 × 10 – 6 × ln p H2O 3 1 − 1,3319669 × 10 – 1 × ln p H2O + 5,6577518 × 10 – 3 × ln p 2 H2O − 7,517286510 × 10 – 5 ln p 3 H2O (7-81)
Where
p H2O water vapor pressure scaled to the relative humidity at the location of relative humidity measurement, T sat = T amb
T dew dew point as determined from relative humidity and dry bulb temperature measurements

---
Source: https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/3/division/3.3/division/3.3.2/division/3.3.2.4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-3/division-3.3/division-3.3.2/division-3.3.2.4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.