The structure of the online viscometer sensor part is shown in the figure. It is mainly composed of sensitive components, probe, main shaft, torsional vibration mechanism, circuit drive, electromagnetic mechanism, coil, crossbar, transmission mechanism, torque tube, flange, etc.

The key to the sensor lies in its ingenious structural design. This structure can be equivalent to a single-degree-of-freedom second-order system, with complex components each performing its own function. The sensitive element, as an important component that directly senses fluid characteristics, closely cooperates with the contact probe to accurately capture fluid changes. The main shaft plays a crucial transmission function in the entire system, while the transmission mechanism ensures the effective transmission of power and motion.

The electromagnetic mechanism and drive circuit provide stable and precise excitation current to the entire system. When the excitation current causes the torsional vibration mechanism to resonate, the powerful resonant energy quickly drives the main shaft to generate torsional vibration. This torsional vibration, like a precise messenger, is quickly and accurately transmitted to the sensitive element through the main shaft, which is an efficient transmission mechanism.

After the sensitive element receives the vibration signal, it synchronizes its vibration with the main shaft and the crossbar. During this process, the change in fluid viscosity is cleverly transformed into a change in the shear stress moment of the sensitive element. This change directly causes an alteration in the sensitive element's motion amplitude. The greater the fluid's viscosity, the more significant its hindering effect on the sensitive element, and thus the more prominent the change in amplitude. Simultaneously, the crossbar, through its meticulously designed mechanical structure, effectively amplifies the sensitive element's amplitude, making changes in amplitude easier to measure and monitor. A microcomputer, with the aid of a differential transformer type displacement sensor, can extremely accurately measure the magnitude of the crossbar's amplitude. Subsequently, through real-time monitoring and analysis of amplitude changes, the increase or decrease of the excitation current is further feedback-regulated. When the amplitude decreases, the excitation current is increased to intensify the vibration; when the amplitude is too large, the excitation current is decreased to restore it to normal. This cyclical alternation precisely controls the sensitive element's amplitude, ensuring it consistently remains stable within a constant resonant frequency and an ideal amplitude range. By measuring the change in excitation current, the processor can accurately obtain the magnitude of the compensation power, and the square of the compensation power is directly proportional to the fluid's dynamic viscosity. Based on specific mathematical relationships, the viscosity value of the measured object can be accurately calculated.