The TUV Model turbines are based on the principle of the Woltmann rotating vane meter. A turbine wheel of negligible mass is concentrically mounted in a pipe and supported by bearings.
The liquid flows through the turbine wheel in the axial direction. The medium flow is smoothed by a flow straightener, and reaches the turbine wheel as a quasi-laminar flow stream.
The speed of the turbine wheel is proportional to the average flow velocity across the pipe cross-section. The rotational speed is thus proportional to the volumetric flow over a wide range.
An inductive transducer screwed into the turbine housing senses the speed of the turbine wheel in a non-contacting manner.
The sensor signal is amplified and converted to produce a pulse signal. The pulse count per time unit is proportional to the actual flow rate.
All turbines are calibrated and delivered with their own calibration reports. Variations in viscosities in your application can be taken into consideration during calibration of the most commonly found viscosities.