Characterisation of hanging and detaching droplets using optical measurement setups

Abstract

This paper presents two measurement setups to analyse hanging and falling droplets from different nozzles. The focus of these setups is on reducing costs and complexity of such systems compared to systems mentioned in literature which consists of an expensive high speed camera with according lens. Therefore the first setup uses an industrial camera and a corresponding lens having a resolution of up to 800 x 600 pixels and enabling the capturing of movies with more than 1000 frames per second (by using a reduced resolution). Additionally a weighing scale is implemented. The second setup represents a real low-cost approach, which nevertheless offers about 120 frames per second and a resolution of 640 × 480 pixels by using two RaspberryPi microcontrollers and the according camera modules. The cameras are placed in an angle of 90°. The presented setups are compared to each other and the advantages and disadvantages of each system are figured out. Subsequently the results of an exemplary measurement of the droplet volume are presented showing the quality of both setups with a maximum deviation of the optical results of less than ± 6 % compared to the results of the weighing scale.