## 3 Results and Discussion
For this group of nozzles, differences were already noted when analyzing the median average values for the entire spray, especially for the measurement time T = (40, 20, 10) s. Figure 9 presents the results of the median volume diameter Dv0.5 expressed by the coefficient of variation for limited test times T = (120, 80, 60) s. For the AirMix 11003 nozzle, the range of variation was 0-5.1%; for the MMA 11003 EZ nozzle, 0-5.4% was recorded; and for the AirMix 11002 nozzle, 0-4.7% was recorded. A marked decrease in the value of the coefficient of variation was found, suggesting greater stability of the volume median values in the adopted measurement time ranges T = (120, 80, 60) s throughout the entire study area. From the point of view of assessments of the droplet size spectrum, it is also important to analyze the values and variability of the volumetric diameters Dv0.1 and Dv0.9 (Figures 10 and 11, Table 2). It is clear that the larger the value of Dv0.1, the lower the drift potential. In contrast, the higher the value of Dv0.9, the lower the number of droplets that provide adequate coverage. The coverage and effectiveness of the spray may be reduced because in some applications, there may not be enough droplets to adequately cover the surfaces being sprayed. When measuring the volume diameter Dv0.9, slight variations in its value were also observed for reduced time values, as follows: (i) AirMix 11003--13.2 \(\mu\)m,  
Figure 9: Volumetric median variation as a function of measurement time, determined by the droplet diameter distribution test with the PDA analyzer. (ii) MMat 11003 EZ--5.4 \(\upmu\)m, (iii) Teejet 11001 VS--3.9 \(\upmu\)m, (iv) MMat 11003 RS--1.6 \(\upmu\)m, and (v) AirMix 11002--13.9 \(\upmu\)m. A similar nature of Dv0.9 variability was observed as in the case of the median volume diameters. As in the case of the median volume diameter, slight differences in the Dv0.9 volume diameter values were observed between T = 120 s and T = 60 s of the test time for nozzles with a dominant spectrum of coarse (C) and medium (M) droplets produced. Figure 11: Values of volumetric diameters Dv0.1 as a function of measurement time, determined from the test distribution of droplet diameters with a PDA analyzer. Figure 10: Values of volumetric diameters Dv0.9 as a function of measurement time, determined from the test distribution of droplet diameters with a PDA analyzer. In the case of measuring the volumetric diameter Dv0.1, small changes were also observed in its value for the reduced value of time. The tests showed the following values: (i) AirMix 11003--2.2 \(\mu\)m, (ii) MMat 11003 EZ--5.3 \(\mu\)m, (iii) TeeJet 11001 VS--0.9 \(\mu\)m, (iv) MMat 11003 RS--2.5 \(\mu\)m, (v) AirMix 11002--4.6 \(\mu\)m. The results of the measurements showed a similar nature of variation as in the case of volume median diameter and volume diameter Dv0.9. Slight fluctuations in the spray spectrum of volume diameters (Dv0.5, Dv0.9, Dv0.1) across almost the entire range of measurement times T = (120, 80, 60, 40, 20, 10) s, provide stable relative span factor (RSF) results. The lower the relative span factor, the smaller the differences in droplet size. When considering the spray process, the phenomenon of liquid drift should be included in the evaluation of the spectrum. Wind has the greatest influence, but the effect of droplet size should also be considered. Small droplets, having a low mass compared to large ones, can stay in the air for a longer time. This results in a higher probability of drift due to wind. Another factor unfavorable to the drift phenomenon is humidity. During low humidity and therefore high temperature, small diameter droplets are exposed to vaporization. In this case, it is also important to evaluate the stability of the coefficient value as a percentage of the total volume of droplets smaller than 100 \(\mu\)m (V100). Despite limiting the measurement time in successive trials, stable and comparable values were obtained for each nozzle tested.