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Viscometer classification

Viscometers commonly used in production processes include rotational viscometers, ultrasonic viscometers and capillary viscometers.

Rotational Viscometer

A viscometer with a rotating measurement system. It has a wide variety: according to the measurement parameters, it can be divided into torque measurement type (rotation speed is constant) and rotation speed measurement type (torque is constant); according to different device structures, it can be divided into coaxial cylinder type and cone-plate type. Figure 1 is a torque measuring viscometer with a coaxial cylinder structure. When the outer cylinder rotates at a certain speed, measuring the torsional moment on the shaft of the inner cylinder can express the viscosity. It can measure viscosity, is suitable for high temperature and high pressure, and is often used in industrial production of chemical fibers, papermaking, resin polymers, etc.

Ultrasonic Viscometer

It consists of ultrasonic detection elements and electronic instruments (Figure 2). When the electronic instrument outputs a pulse current to excite the iron-cobalt-vanadium shrapnel immersed in the measured liquid, due to the magnetostrictive effect (see piezomagnetic sensor), a mechanical vibration that decays with time is generated. The viscosity of the liquid can be expressed by measuring the decay speed of the shrapnel in the liquid by the measuring circuit. The detection element is resistant to temperature up to 300°C, and is also resistant to high pressure and corrosion. Suitable for chemical, petroleum, paper, rubber, plastic, paint and heavy oil burner control, etc.

Capillary Viscometer

An instrument for measuring fluid viscosity using a capillary tube. The behavior of fluid flowing through a capillary is described by the Poiseuille equation:     η= (πr to the fourth power pt)/(8lv)     where η is the viscosity coefficient, r is the radius of the capillary, and l is the capillary length, P is the pressure difference between the two ends of the capillary, v is the volume of the liquid flowing through, and t is the flow time. There are many measurement methods of this viscometer. It can measure the time for a certain volume of liquid to flow through the capillary under a certain pressure difference, and it can also measure the volume of the liquid flowing out of a certain pressure difference per unit time. It can also specify a certain flow to measure the capillary. pressure difference between the two ends. The viscometer in Figure 3 uses a metering pump to pass the measured liquid through the capillary tube at a certain flow rate, and then measures the pressure difference between the two ends of the capillary tube by a differential pressure gauge, which can indicate the viscosity value. Capillary viscometer has a wide measurement range, high precision, simple and easy maintenance, and can be used for high pressure, but it requires high cleanliness of the liquid to be measured. Suitable for measuring lubricating oil, fuel oil, etc.