Grain yield monitor
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.
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.
[1][3] 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.
Improvements in this area have resulted in the use of multi-point calibration to provide a more accurate characterization of the load cell response.
[5] Excessive wear of the clean grain elevator paddles over time will also affect the mass flow calibration.
Harvesting on slopes decreases the accuracy of the mass flow sensing system in most cases.
This sensing method provides high accuracy to within 2% when calibrated, but exposes operators to possible radiation exposure.
[7] A light emission source coupled with a receptor is placed opposite of each other at the top of the clean grain elevator.
[2] Difficulties of this system are lower accuracy at higher grain flow rates and uneven loading of the elevator paddles.
Grain moisture content at harvesting is an important piece of the yield monitoring process.
It is used in many cases, dependent upon manufacturer, in the grain mass flow sensor calibration and provides producers with additional information about spatial variability within a field.
[7] This sensor orientation allows for sampling grain moisture throughout a field during harvest operations.
In the United States the grain yield is typically reported as bushels per acre.
SI units for grain yield measurement are typically reported as tonnes per hectare or in few cases m3.
The operator can enter additional information to separate and identify yield data from different fields and farms.
These software packages allow for viewing of the yield maps and completing other analysis of the data.
Grain yield monitors have been in production since yield monitors were introduced in the early 1990s and have been progressively updated with better hardware that provides the harvester operator with a better user interface and makes the logged data information more readily available.
These errors are present from issues listed in the "Impact Based Mass Flow Measurement" section of this page.
Hawk et al., "Grain Mass Flow Sensor For An Agricultural Combine", published 1997-11-11, assigned to Deere & Company, Moline, IL(US)
