All thermometers need to be protected within a case to dampen the effect of direct radiation to achieve a valid air temperature. Some are additionally cooled by a fan, usually with a wind speed of 2 m s-1 approximatively. Temperature is measured by means of highly sensitive resistors (Pt100 or similar).
Humidity at the station "Basel - Lange Erlen" is measured by a psychrometer, with the issue, that at low temperatures the measured values are not reliable (since the wet sock simply freezes in winter). At "Basel Klingelbergstrasse", humidity is measured by means of a Thygan, a dew point mirror.