What is a cone-plate viscometer?

Cone-plate viscometer is a common rotary viscometer.

Viscometer is a physical analysis instrument for measuring fluid viscosity. Viscosity is a physical property of fluid substance, which reflects the internal friction between molecules when the fluid is acted by external force. The viscosity of a substance is closely related to its chemical composition. In industrial production and scientific research, the composition or quality of substances is often monitored by measuring viscosity. For example, in the production of polymer materials, viscometer can be used to monitor the viscosity of synthetic reaction products and automatically control the reaction end point. Others, such as automatic control of petroleum cracking production process, lubricating oil blending, monitoring of certain foods and medicines, pipeline transportation of crude oil, quality inspection of various petroleum products and paints, etc. Viscosity measurement is required.

According to the working mode, there are three types: capillary type, rotary type and vibration type.

According to the working mode, it is divided into offline viscometer (sampling detection), online viscometer (24-hour continuous measurement) and portable viscometer.

Capillary viscometer: Capillary viscometer is usually Saybolt viscometer, which is a common viscometer. Its working principle is: the sample container (including the outflow capillary) is filled with the sample to be tested. In the constant temperature bath, the height of the liquid column is h, the cock is opened, the sample begins to flow to the liquid receiver, and the time is counted until the liquid level of the sample reaches the calibration line. The greater the viscosity of the sample, the longer the time. Therefore, this time directly reflects the viscosity of the sample.

Rotary viscometer: The commonly used rotary viscometer is cone-plate viscometer. It mainly includes flat plate and cone plate. The motor drives the flat plate to rotate at a uniform speed through the speed change gear, keeps the sample to be measured between the two plates through capillary action, and drives the conical plate to rotate through the friction between sample molecules. Under the action of the torsion spring in the torque detector, the cone plate does not rotate after rotating for a certain angle. At this time, the torque exerted by the torsion spring is related to the molecular internal friction (i.e. viscosity) of the tested sample: the greater the viscosity of the sample, the greater the torque. There is a variable capacitor in the torque detector, and its rotor rotates with the cone plate, thus changing its capacitance value. The torsion spring torque reflected by this capacitance change is the viscosity of the measured sample, which is displayed by the instrument.

Rotary viscometer has the advantages of convenient use, stable performance and simple maintenance, and is suitable for measuring the viscosity of various fluids such as oil, paint, ink, coating, plastic, slurry, rubber, latex, detergent, resin, condensed milk, cream, medicine and cosmetics. Used in textile, chemical industry, petroleum, electromechanical, medicine, food, light industry, construction and other industries as well as colleges and universities.

After the rotary viscometer is turned on, the zero position should be detected first. This operation is usually carried out without installing the rotor. Then an inner cylinder with a radius of R2 is coaxially installed in the outer cylinder with a radius of R 1, and the inner cylinder is filled with viscous fluid. The synchronous motor rotates at a steady speed, scales the discs in turn, and then drives the inner cylinder (that is, the rotor) to rotate through the hairspring and the rotating shaft. The inner cylinder (that is, the rotor) bears the viscous torque based on the fluid, and the greater the effect. Multiply the reading by a specific coefficient to get the dynamic viscosity of the liquid.

Vibration viscometer: The working principle of this viscometer is that when an object in a fluid vibrates, it will be hindered by the fluid, and the magnitude of this action is related to the viscosity of the fluid. The commonly used vibration viscometer is ultrasonic viscometer, and its detector has a spring piece. Under the excitation of pulse current, the shrapnel produces mechanical vibration in the ultrasonic range. When the elastic sheet is immersed in the tested sample, its amplitude is related to the viscosity and density of the sample. When the density is known, the viscosity value can be obtained from the measured amplitude data.