Viscous Damping Coefficient Measurement System Using Incremental Optical Encoder

We built a viscous damping coefficient measurement system that applies the principles of underdamped harmonic oscillation within viscous liquid. The scientific novelty of this paper lies on the type of sensor used to capture the oscillation. An incremental optical encoder is chosen as a motion detector due to its ability to convert angular position as well as rotation direction into a pair of square wave signals. The harmonic oscillator system consists of a spring with the spring constant value of 82.8 N/m, a 1.50 kg cylindrical mass and a 95.0 g prolate ellipsoidal mass. The data acquisition system converts the encoder output pulses into counts which represent the displacements of the oscillating mass under viscous liquid. We used a Proportional Integral Derivative (PID) temperature control system to maintain the sample temperature at a constant value. Experimental data suggests that the air resistance and the total friction of the mechanical components give good contribution to the damping effect of the mass’ harmonic oscillation. The repeatability test of the viscous damping coefficient measurement resulted 1.26975744 % of relative standard deviation