Finally, we discuss the problem of temperature calibration, presenting techniques that allow the determination of the true sample temperature for a given set temperature of the rheometer. In particular, we present recommendations based on experience from various laboratories. Prerequisites for sample preparation and loading are addressed. Viscoelastic reference samples are also discussed. Relevant issues, predominantly for Newtonian reference liquids, are the exploration of measurement limits, related either to the shear rate range or to reliably accessible viscosity levels. Sources of reference fluids with defined viscosities are presented, and their use in tests for verification of accuracy is demonstrated. After summarizing the relevant definitions and test modes, we show examples of measurements in the linear viscoelastic range, and applications of the Cox–Merz relationship. We focus on the determination of the viscosity as a function of the shear rate and of the magnitude of the complex viscosity as a function of the angular frequency. The paper addresses techniques for checking the performance of rotational rheometers with cone–plate, plate–plate, or concentric cylinder geometry.
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