Model HTD13285 Digital rotational viscometer is a type of viscosimeter newly designed by our company. The viscometer is designed with embedded configuration，It is equipped with a high-precision Angle sensor, driven by a stepper motor, and the speed is more stable and accurate；The buttons on the panel are easy to operate，High resolution LCD screen can display the float rotation Angle and stirring speed in real time. This product can be widely used in petroleum, chemical, food, medicine, cosmetics and other industries.
The introduction of the working principle：Put the slurry cup filled with liquid on the tray，The liquid enters the annular space (shear gap) formed between the external outer sleeve and the floater of the viscometer. When the motor drives the outer sleeve to rotate，The outer sleeve in the liquid is subject to the force applied back to viscous resistance，the force can produce torque to the floater in the outer sleeve through the liquid under test in the annular space. The floater is attached to the Angle sensor，when the torque is balanced with the viscous resistance，the Angle sensor will detect the Angle of floater rotation. Due to the Angle of the floater rotation is directly proportional to the viscous resistance of the outer sleeve， the sensor's Angle value is multiplied by a specific coefficient to get the final viscosity，and the Angle value of the sensor is also displayed on the LCD screen for reading.
The shear rate and viscosity have a linear relationship，in other words, the relation between shear stress and shear rate is a straight line. In practice, many fluids do not follow the Newton's law. But its rheology is closer to Newton's law, so that it can be measured by a viscometer and the test result will be more accurate. The calibration mode of the Model HTD13285 Digital Rotational Viscometer is Linear calibration of the Newton mode, Which is not suitable for the samples do not conform to the Newton linear calculation method. In this case, the measurement of the viscosity and the calculation of the velocity should use the Nonlinear computing methods.
When the instrument operates at the rate of 300r/min，The measurement unit of the viscometer is cP or mPa.s. The data measured at other speeds can be converted. The sixth part of this paper presents a method for calculating the viscosity of pseudo-plastic fluids,such as drilling fluids.
When different rotating speeds are selected or different combinations of torsional spring and float are used，the optional range of shear rate may change. To widen the shear stress's range and test more fluids，it can be solved by replacing different kinds of torsion springs.