Viscosity is a measure of a fluid's resistance to deformation or flow. In simpler terms, it refers to how thick or thin a fluid is. Viscosity is defined as the ratio of shear stress to shear rate when a fluid is subjected to uniform shearing.

Figure 1. SME-TRD with SRV probe


1. How is Viscosity measured with the SRV?

The rheonics SRV measures viscosity by means of a balanced torsional resonator, one end of which is immersed in the fluid under test. The more viscous the fluid, the higher the mechanical damping of the resonator. By measuring the damping, the product of viscosity x density may be calculated by rheonics' proprietary algorithms.

Figure 2. Rheonics probe response when immersed in fluid.

2. What Units are available as output from Rheonics process viscometer SRV?

These diverse viscosity units are crucial for ensuring accurate and standardized communication of material properties across different fields. The choice of unit depends on the specific characteristics of the substance being measured and the industry or discipline in which the measurement is applied.

  1. mPa·s (millipascal-second):

    • Description: This unit represents viscosity measured in millipascal-seconds. It is a metric unit of dynamic viscosity.

    • Importance: mPa·s is crucial for precise measurements of dynamic viscosity, particularly in scientific research and industrial applications. It provides a standardized and convenient unit for expressing viscosity in a metric context.

  2. cP (centipoise):

    • Description: Centipoise is a unit of dynamic viscosity in the centimeter-gram-second (CGS) system, representing one-hundredth of a poise.

    • Importance: Centipoise is widely used in industries where the viscosity of fluids significantly impacts product quality. It is particularly valuable in fields such as pharmaceuticals, cosmetics, and petrochemicals for quality control and product development.

  3. Pa·s (pascal-second):

    • Description: The pascal-second is the SI unit of dynamic viscosity. It is equivalent to one newton-second per square meter.

    • Importance: As the SI unit of dynamic viscosity, Pa·s is fundamental in scientific research, engineering, and fluid dynamics. Its use provides consistency and compatibility across various disciplines, ensuring accurate and standardized measurements of fluid behavior.

  4. Poise:

    • Description: The poise is the CGS unit of dynamic viscosity, equal to one dyne-second per square centimeter.

    • Importance: The poise is essential for historical and specific contexts, especially in older literature and applications where the CGS system is still relevant. It serves as a valuable unit for expressing dynamic viscosity in the centimeter-gram-second system.

  5. Reyn:

    • Description: The Reyn is a unit of dynamic viscosity in the British Gravitational System (BG), where 1 Reyn is defined as the viscosity of 1 pound-force second per square foot.

    • Importance: While less common today, the Reyn is historically significant in the British Gravitational System. It may be encountered in older literature and certain specialized fields. Understanding the Reyn can be important for interpreting and converting data from historical sources that use this unit.

Understanding and measuring viscosity is crucial in various industries to ensure the proper functioning of fluids in processes ranging from manufacturing to transportation. The choice of unit depends on the specific requirements of the application and the preferred system of measurement.

3. Why is it important to measure viscosity?

Viscosity measurements are vital in characterizing materials for research and development purposes. In the petroleum industry, viscosity assessment ensures the quality of crude oil and lubricants. It optimizes industrial processes by enhancing efficiency in mixing and pumping

Measuring viscosity is crucial for quality control in manufacturing various products, including pharmaceuticals and cosmetics. 

Environmental monitoring utilizes viscosity measurements to assess water quality and detect contaminants. Viscosity is fundamental in predicting fluid flow for engineering applications. Industries such as food processing and printing depend on viscosity control to achieve desired product consistency and quality.

4. References