Since the early 1990s, the department has been operating a daylight measuring site which, in recent years, has been reactivated and expanded as part of the project “Use of Daylight in Buildings IV” funded by the Federal Ministry of Economic Affairs and Energy (project code: 03ET1148B). The intensive use of the measuring site, upcoming research activities and structural needs required a new concept, which is currently being implemented. 

The core of the measuring site is its spectral sky scanner, which has been performing spectrally and spatially resolved measurements since October 2014. In the first half of 2017, its functionality was tested and the associated calibration was carried out.

Every two minutes, the following radiometric and photometric parameters of daylight are recorded and evaluated at the daylight measuring site by means of different measuring devices: 

• global irradiance (pyranometer – Kipp & Zonen)
• direct solar irradiance (pyrheliometer – Kipp & Zonen)
• direct solar illuminance (luxmeter with tube – TU Berlin)
• horizontal and four vertical illuminances (daylight photometer head – PRC Krochmann)
• luminance of 145 sky patches (luminance sky scanner – PRC Krochmann)
• spectral radiance of 145 sky patches (spectral sky scanner – Czibula & Grundmann)

The measurements are used to create data sets for lighting design, product development and research. In addition, they are used to characterize the light source ‘daylight’ in order to find out which properties make it the preferred light source.