Evaluation of an optical sensor for tuber yield monitoring

A sensor for monitoring the yield of tubers was tested in the laboratory and in the field. The laboratory test was designed to investigate whether the sensor varied in its measurements of tuber size, whether the recorded size differed within the width of the sensor, and whether tilting of the sensor affected the result. The test objects were spheres, and measurements were carried out on three different sizes. A statistical analysis showed how the sensor measured the sizes for the different combinations of size, position, and inclination. In the field, a harvester-mounted sensor was used to monitor yield of Bintje potatoes in terms of tuber size and weight. The results obtained were compared with those from mechanical load-cell measurements. An expression relating tuber size to weight was determined. Plot-harvesting tubers provided data for evaluation of tuber size in relation to yield. The results showed that the errors in size determination by the sensor were in the order of 1% to 2%. Different size classes were well differentiated. Some differences were noted for object position and sensor inclination. Field tests showed that the mean deviation from measured weight was about 1%. It was concluded that sensor errors were small and that the sensor could discriminate between different sizes for the spheres used in the study. In the field, the sensor worked with good consistency and is a potential option for tuber yield monitoring.