Grain yield monitor

The combine grain yield monitor is a device coupled with other sensors to calculate and record the crop yield or grain yield as a modern day combine harvester operates. Yield monitors are a part of the precision agriculture products available to producers today that provide producers with the tools to reduce costs, increase yields, and increase efficiency. The present day grain yield monitor is designed to measure the harvested grain mass flow, moisture content, and speed to determine total grain harvested. In most cases today this is coupled with global positioning system to record yield and other spatially variable information across a field. This allows for the creation of a grain yield map which provides information on spatial variability and supports management decisions for producers.

Grain Mass flow is most commonly measured using a load cell with an impact plate attached to the load cell located at the top of the clean grain elevator. As the clean grain elevator paddles rotate around the top of the clean grain elevator, the grain is expelled from the elevator by centrifugal force and makes contact with the impact plate attached to the load cell. The force applied by the grain is converted to an electrical signal by the load cell that is used to estimate the mass flow of the grain. A calibration of the sensor to develop a relationship of the amplitude of the electrical signal to grain mass flow and is calibrated on a harvester specific basis with the grain mass reported on a wet basis. This technology was developed and first commercialized by Ag Leader Technology. The clean grain elevator speed is also measured and used in the calibration from electrical signal to mass flow as the elevator has a direct impact on the amount of force applied to the impact plate and load cell. This is the most common method for measuring grain flow in harvesters today and exists in different variations.

The grain mass flow sensor must be calibrated to provide an accurate estimation of grain flow from the electrical signal produced by the load cell. Different models of the grain mass flow sensor use different methods of calibration, with some being as simple as a linear single point calibration. Improvements in this area have resulted in the use of multi-point calibration to provide a more accurate characterization of the load cell response.

The calibration process entails harvesting consistent crop at a constant speed to produce a consistent grain mass flow rate to the mass flow sensor. A calibration is started through the yield monitor installed on the harvester and the operator begins harvesting grain. Once the recommended amount of grain harvested per the manufacturer's recommendations has been harvested, the grain is offloaded into a grain holding device equipped with an accurate scale to measure the actual weight of the grain harvested. This grain weight is then entered back into the yield monitor and is used to adjust the calibration that relates the electrical signal of the load cell to grain mass flow.

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