Contactless Determination of the Number and Diameter of Fog Droplets Using Gravitational Separation and Measurement of Electrical Signals

  • 1 Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria
  • 2 Institute of Electronics, Bulgarian Academy of Sciences, Sofia, Bulgaria
  • 3 Escuela Politécnica Superior, Universidad de Alcalá, Madrid, Spain
  • 4 Institute of Mechanics, Bulgarian Academy of Sciences, Bulgaria


A method was developed for contactless evaluation of the number and diameter of droplets in a jet, by means of gravitational separation and measurement of an electrical signal from a laser-induced electromagnetic echo effect (EMEE), at several points of the jet. With it, only with modulated laser radiation, an electrical signal is induced. The measured value of the signal from this EMEE depends on the parameters of the fog (number and sizes of droplets). This signal is measured at several points of the jet, as the droplets must be in laminar flow. After measuring the signal at the first point, the signals at the previous points are subtracted from its value at each subsequent point, in order to separate the measured signal at each point and determine the change in fog parameters. The method represents an affordable and reliable alternative to existing fog characterization techniques.



  1. I. G. Droppo, Filtration in Particle Size Analysis, In book: Encyclopedia of Analytical Chemistry: Applications, Theory and Instrumentation, R. A. Meyers and R. B. Flippen (Eds.), (2006) doi:10.1002/9780470027318.a1506
  2. S. Andrews, D. Nover, G. Schladow, Using laser diffraction data to obtain accurate particle size distributions: the role of particle composition, Limnology and Oceanography Methods, 8(10), 507- 526 (2010) doi:10.4319/lom.2010.8.507
  3. H. Chen, H. Tang, Y. Liu, H. Wang, G. Liu, Measurement of particle size based on digital imaging technique, Journal of Hydrodynamics, 25(2), 242-248 (2013) doi:10.1016/S1001- 6058(13)60359-5
  4. O. Ivanov, P. Todorov, J. L. Pérez-Díaz, Non-contact determination of the number and diameter of fog drops, by means of gravitational separation and measurement of electrical signals, patent No. 67164 B1, Patent Office of Republic of Bulgaria (issued on 10.12.2020)

Article full text

Download PDF