Viscosity coefficient is one of the important properties of liquid. Measurement of liquid viscosity coefficient using a falling sphere can reveal related physical phenomena clearly. Normally, the measurement accuracy of the falling ball method is not high by using a manual stopwatch considering the existing parallax errors of the sphere.

 This apparatus is designed with the following benefits:

 1. Using photoelectric sensor and electronic timer to avoid the parallax and timing errors caused by a stopwatch

2. Improved mechanical design to ensure precise falling trace of the sphere

3. Using laser ranging to accurately measure both the fall time and fall distance to avoid the parallax error

 Using this apparatus, the following experiments can be conducted:

 1. Measure the viscosity coefficient of a liquid using falling sphere method

2. Use a photoelectric sensor for timing experiment

3. Use a stopwatch to time a falling sphere, and compare results with the photoelectric timing method