1.6 Measurements principles a) Optoelectronic sensing of the liquid meniscus The near-infrared light which is generated in LEDs located in the upper section of the measurement stand AVs/S is conducted through a glass-fibre light-conductor cable onto the measurement planes The light shines through the viscometer before it arrives at another light-conductor cable located on the opposite side; inside this second cable, the light is conducted to a receiver in the upper section of the measurement stand. While the liquid meniscus passes through the measurement planes, the lenslike effect of the meniscus causes a short-term darkening of the light beam, followed by a magnification. This process generates a measurement signal which can be evaluated accurately.