Analysis on instantaneous measurement of a hydrodynamic viscometer using an eddy current sensor

This thesis is dedicated to the improvement of the measurement principle of a hydrodynamic viscometer, as to progress towards instantaneous measurement.
The analysis focuses on the electronic precision distance measurement, which is realised by the use of an eddy current sensor with parallel resonance circuit in this device and represents a central part of the measurement chain to determine the viscosity value.
In the first part of this thesis the worst-case deviation of the measurement value, caused by the influence of temperature and aging on the analogue components, is quantitatively estimated. Subsequently, within the scope of the second part of the thesis, digital measurement signal processing is analysed regarding its optimization by the use of theory on the concept 'digital lock-in amplifier', reviewed within this project.
As a result of the considerations regarding optimisation the 'projection method' is presented, which enables the extraction of additional information from the analogue system, utilizing signal phase measurement as well as multi frequency excitation of the parallel resonance circuit, in order to reduce the influence of dynamic component drifts on the measurement signal.