# Design and Construction of a Low-Cost Test Bench for Testing Agricultural Spray Nozzles
## 4 Conclusions  
The design, development, and construction of a low-cost laboratory test bench suitable to analyze agricultural spray nozzles according to the ISO 5682-1 procedure were discussed in the paper. The preliminary tests show its usefulness under several aspects:  
* The software interface to control the test bench and to set the test conditions is simple, and its organization in tabs (the first to set the test parameters; the second one to see graphically the evolution of the test variables) makes it easy to use the test bench. * The hydraulic circuit allows for testing nozzles under work conditions similar to those present in commercial sprayers, using a standard diaphragm pump and standard manual pressure regulators. * The electromechanical components allow for a fine and precise control of speed and position of the nozzle under test. * The image acquisition system, based on a digital single-lens reflex camera, may be easily updated if higher resolutions are required. The actual system, with a scale factor of 188.0-189.0 pixel/mm, allows for detecting the drops whose diameter is greater than 10 \(\upmu\)m, which can be considered suitable for similar applications. * In measuring the single drop diameters, it is possible to devise the size diameter probability distribution function and all the usual spray drop parameters. The preliminary tests with the Albuz ATR80 orange hollow cone nozzles produced results in accordance with factory data sheets. * Further tests that are aimed at comparing several nozzle types (hollow cone, fan, air induction) with the reference nozzles recommended by ISO/FDIS 25358:2018 [55] to define the boundaries/borders between the size classes may better assess the capabilities of the test bench. The system also has some limitations due to the specific hardware implementation. The most severe limitation is imposed by the rail length, which does not allow for the maximum speed of the mobile platform, while spraying above the Petri dishes, to be higher than 1.5 m/s. Higher speed values to be kept constant while the nozzle sprays above the Petri dishes would require higher acceleration values, but the maximum acceleration is limited for mechanical/electrical safety reasons. Increasing the platform speed is a practical way to reduce overlaps between drops and then to simplify the subsequent image analysis procedure. A minor limitation is related to the maximum sample rate of the Advantech Ethernet modules, used for monitoring the position and speed profile and for acquiring data from sensors. The trajectory control loop is achieved via hardware with a 1 kHz sampling frequency, but monitoring and logging operations are left to the Windows operating system, which cannot guarantee a constant sampling rate and good accuracy for time intervals less than 100 ms; thus, the speed and position graphs may result deformed. An optimization of the reading and writing routines and of data filtering may improve these aspects. Finally, a significant improvement may be introduced in the camera positioning system. The camera is actually applied to a metallic frame, which in turn is manually hanged to the rails in predetermined positions. A better solution could be to hang the camera directly to the mobile platform after the spray passes and then to position it in correspondence of the Petri dishes by exploiting the control position system of the motor. This could speed up the image acquisition procedure and then reduce any effect of external factors. Finally, taking into account all the above considerations, it is possible to conclude that the main objectives fixed were achieved with the test bench and that its modularity allows for further developments to overcome the limitations highlighted, without compromising the low cost. Conceptualization, E.C., D.L., G.M., and R.P. ; methodology, E.C., D.L., G.M., and R.P. ; software, D.L. ; validation, E.C., D.L., G.M., and R.P. ; formal analysis, E.C., D.L., G.M., and R.P. ; investigation, E.C., D.L., G.M., and R.P. ; data curation, E.C., D.L., G.M., and R.P.