Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/1999
Publication Date: N/A
Interpretive Summary: Various types of sensors are used to measure the amount of grain that passes through a combine during harvest. Measurement accuracy is important because the measured grain yield is used to determine the amounts of agricultural input to be applied to different parts of a field. Doing so may help optimize the yield in different regions in a field. However, the yield sensors are very sensitive to calibration procedures, changing crop properties, and field roughness and slope variations. The experiments done in this study showed that x-ray techniques could overcome these difficulties to achieve consistent, high accuracies. X-rays are not sensitive to grain moisture and are not affected by changes in grain-flow profile. The x-ray measurement system does not require frequent calibrations during operations since the most important factors that affect the accuracy of some other types of sensors are eliminated. Farmers will find such x-ray sensors to be very useful.
Technical Abstract: The use of low energy bremsstrauhling x-ray, 30 KeV, densitometry is demonstrated for grain flow rate measurements. Constant mass flow rates for corn are related to measured x-ray intensity with a 0.99 correlation coefficient for flow rates ranging from 2 kg/s to 6 kg/s. Higher flow rate values can be measured by using slightly more energetic x-rays or a higher tube current. Measurements were done in real time taking approximately 20 ms. Measurements are independent of grain moisture (due to a negligible change in the x-ray mass attenuation coefficient at typical moisture content values from 15% to 25%). Grain flow profile changes do not affect measurement accuracy. X-rays easily capture variations in corn stream. Due to the low energy of the x-ray photons, biological shielding can easily be accomplished with 2 to 3 mm lead foil.