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1.7
Measurement principles
a) ViscoPump VZ 8561: Optoelectronic sensing of the liquid meniscus
The near-infrared light which is generated in LEDs located in the upper section of the measurement stand
is conducted through a glass-fiber 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 lens-like 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.
Fig.1 Viscometer for optoelectronic measurements
b) ViscoPump VZ 8562: Viscometer with thermistor sensors (TC viscometer)
In the case of TC viscometers, glass-coated thermistors serving as sensors are inserted on the level of
the measurement planes. While the meniscus passes through the measurement planes, the differences in
the thermal conductivity properties of air and liquid lead to a change in the heat balance. The thermistors
of the TC viscometers are inserted hermetically tightly into the glass coating of the viscometer.
Fig. 2 Viscometer for optoelectronic measurements
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