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We investigated the vibration characteristics of the torsional oscillation mode of an earlier proposed resonant viscosity sensor based on vibrating pipes. To do so, the sensor housing is opened, so that half of the resonator is freely accessible. The actuation and readout of the sensor is realized with electromagnetic coils on the remaining part of the housing and the oscillation velocity is measured on different positions on the uncovered sensor surface. We demonstrate the feasibility and suitability of the electromagnetic readout principle and identified an additional spurious oscillation. All measurements were performed with an air filled resonator to minimize the damping and maximize the oscillation amplitudes.

We present a measurement system where a spherical permanent magnet is levitated in an actively controlled magnetic field. The sensor system measuring viscosity and density independently. In operation mode, the magnet is held in a constant levitation position. Due to a special actuation scheme, the magnet rotates around its vertical axis. Using this setup and immersing the magnet in a fluid, it is possible to analyze viscosity and density of all kinds of fluids, except ferrofluids. The magnetic levitation system avoids any connection penetrating the walls of the measurement chamber; only the spherical permanent magnet measurement body is in contact with the sample fluid. Due to this, the measurement procedure is reproducible, repeatable and resource saving.

In this paper we present a new balanced flowthrough viscosity sensor working with a torsionally resonating pipe. The whole system is machined in aluminum and is designed to be placed in the pipes of a chemical production plant. The quality factor Q and the resonance frequency fr are used as measures for the viscosity and density. We describe the sensor setup, its working principle for different resonant modes, the actuation and the readout of the sensor and present first measurement results for liquids featuring different viscosities.