Sensors are located in the seed hoses. The seeds flow through the sensors, which are equipped with six optical transistors. These are illuminated with infrared light. When a seed passes a ray of light, the light is very briefly interrupted and the optical transistor registers a break in the flow of light.
The total number of breaks is registered and processed, enabling the seed volume to be specified with high accuracy. The sensors count rape with approximately 99 percent accuracy. The value for wheat and other grains is approximately 98–99 percent at 250 seeds per second. The system automatically sets accuracy and compensates for the dust and residue that can gather in the sensors.
“Counting seeds is more exact than by calculating quantities based on seed weight,” says Crister Stark. “The system has been developed as a direct response to farmers’ needs to predict total plants per square metre.”