초록 ▼

Viscosity of small fluid samples is measured by coupling an ultrasonically energized shear transducer to a fluid sample through a polymeric coupling layer having a thickness and shear impedance such as to produce a zero total reflection coefficient at least at one particular viscosity. In general, t

Viscosity of small fluid samples is measured by coupling an ultrasonically energized shear transducer to a fluid sample through a polymeric coupling layer having a thickness and shear impedance such as to produce a zero total reflection coefficient at least at one particular viscosity. In general, the thickness will be slightly greater than one-quarter wavelength. The use of the coupling layer produces a large increase in sensitivity, eliminates the need for sophisticated and expensive electronic circuitry, and makes it possible to determine viscosity by very simple circuitry responsive to transducer current.

대표청구항 ▼

Apparatus for determining the viscosity of a fluid sample comprising: an electromechanical transducer having a face capable of vibrating in shear mode when excited by an alternating electrical current; electrical current generating means connected to said transducer for applying an alternating elect

Apparatus for determining the viscosity of a fluid sample comprising: an electromechanical transducer having a face capable of vibrating in shear mode when excited by an alternating electrical current; electrical current generating means connected to said transducer for applying an alternating electrical current of predetermined frequency to the transducer and thereby exciting the transducer into shear vibration; a solid coupling layer of substantially uniform thickness having one face in contact with said face of the transducer and having its opposite face free to come into contact with a fluid sample; and means, connected to the current generating means, for measuring the magnitude of the impedance of the system consisting of the transducer, coupling layer and fluid sample as presented to the generator; wherein the thickness and shear impedance of the coupling layer are chosen so that, at least at one viscosity of a fluid sample in contact with said opposite face of the coupling layer, and at the frequency of said alternating electrical current, the magnitude of the shear wave reflected into the transducer through the interface between the coupling layer and the transducer is substantially zero.