According to the present state of the art “in situ, real-time control systems” are absolutely necessary in modern applications within the field of Thermal Spray technology with regard to the quality and reproducibility of thermal spray coatings for a wide range of industrial applications. Compared with the already existing diagnostic systems and their algorithms which are developed on the basis of CCD cameras, an algorithm can be developed for in situ, real-time control systems, which possesses a by far closer physical approach for the determination of the particle characteristics due to the measurement principle. Thus, about 300 particles can be detected per millisecond as well as average particle velocities within the range of 30 - 1200 m/s and average particle surface temperatures between 700 - 3000 °C can be determined. A statistical distribution of approximately 3000 particles is considered for the computation of the online measured average particle velocities and surface temperatures. The accuracy of the measurement determines the use of an online process control during Thermal Spray processes.