Searle cylinder geometry

Figure 6.6 Geometry of a Searle-type concentric cylinder sensor.

Viscometers are being increasingly used for accurate measurements on modern industrial paints, especially waterborne paints. Rotating viscometers with a concentric cylindrical geometry (Searle system. Fig. 9.1) are advantageous for paints. Precise thermostatic control is easily achieved because the outer cylinder does not rotate. The drive and torque sensor are combined to form a single unit with the rotating inner cylinder. 

Figure 6.5 shows a Searle-type arrangement in which a sample is placed into the gap between the cyhnders. An illustration of the geometry of the cyhnders is given in Figure 6.6, in which the outer cylinder has an internal radius of R while the inner cylinder has a radius offR the gap dimension is / ( — /). The motor causes the inner cylinder to rotate while a measuring spring allows the torque produced... 

Used for glass, sol-gels, blood, polymers, etc. The cup-and-bob types define the volume of sample to be sheared in a test cell. The torque needed to achieve a particular rotational speed is measured. The two geometries are known as the Couette or Searle systems the difference depends on whether the cup or bob rotates. The cup can be a cylinder. 

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