1. According to the mode of operation: capillary, rotary and vibrating.
Capillary viscometers: Capillary viscometers are typically viscometers, a common type of viscometer. Its working principle is: the sample container (including the outflow capillary) is filled with the sample to be tested, is in a constant temperature bath, and the height of the liquid column is h. When the cock is opened, the sample begins to flow to the receiver and the time is calculated until the sample level reaches the mark line. The greater the viscosity of the sample, the longer this period. Therefore, this time directly reflects the viscosity of the sample.
Rotary viscometer: A common rotary viscometer is a cone-plate viscometer. It mainly consists of a flat plate and a cone plate. The motor drives the plate to rotate at a constant speed by the speed change gear, and the sample to be measured is held between the two plates by capillary action, and the cone plate is rotated by the friction between the molecules of the sample. Under the action of the torsion spring in the torque detector, the cone plate does not rotate after being rotated by a certain angle. At this point, the torque applied by the torsion spring is related to the intramolecular friction (ie, viscosity) of the sample under test: the higher the viscosity of the sample, the greater the torque. The torque detector is provided with a variable capacitor whose rotor rotates with the cone plate, thereby changing its own capacitance value. The torsion spring torque reflected by this capacitance change is the viscosity of the measured sample and is displayed by the meter.
Vibratory viscometer: The working principle of this viscometer is that when an object in a fluid vibrates, it is hindered by the fluid. The size of this effect is related to the viscosity of the fluid. The commonly used vibratory viscometer is an ultrasonic viscometer with a shrapnel inside the detector. When excited by a pulsed current, the shrapnel produces mechanical vibrations in the ultrasonic range. When the shrapnel is immersed in the sample under test, the amplitude of the shrapnel is related to the viscosity and density of the sample. With known density, the viscosity value can be determined from the measured amplitude data.