During the past 15 years, interest in generation and analysis of yield maps has grown.  Early work was directed toward development of grain yield monitors, and these systems have become fairly common.  As yield mapping gained popularity among producers, many researchers began concentrating on development of yield mapping systems for other crops.  Documenting yield site-specifically often requires measuring product flow rate as the crop is harvested.  Researchers working in The University of Tennessee Sensors and Controls Lab began developing a sensor for measuring cotton flow rate in harvester applications in the early 1990s.  This work eventually involved cooperation with J.I. Case Corporation and Ag Leader Technology, Inc., and culminated in the commercial release of a cotton yield monitor in 2000.

The system developed in the UT Sensors and Controls Lab is optically-based.  Infrared light is projected into cotton conveyer pipes, and light transmission is measured by optical sensors.  As cotton flows between light emitters and detectors, intensity is reduced, and the measured reduction is used to estimate volumetric cotton flow rate.  The design is patented (U.S. Pat. No. 5,920,018), and used for cotton flow rate measurement in the Ag Leader Technology cotton yield monitor.

Sensors and Controls Lab personnel field-tested the cotton flow rate measurement system in Tennessee during three harvest seasons.  System performance was evaluated by harvesting loads of cotton, integrating flow rate measurements over time to obtain a predicted load weight for each load, and comparing the predicted weight values with actual weight values acquired using scales.  Integrated flow rate measurements consistently predicted actual load weights with a mean absolute (unsigned) error of 4.0% for all of the loads harvested during the tests.  The mean error (signed) was –0.1% with a sample standard deviation of 5.1%.  Sensors were never cleaned during any of the harvest seasons, and performance degradation due to debris accumulation on sensor faces was not observed.

Moody, F. H. 1998. Development and evaluation of a real-time cotton flow rate   sensor. M.S. thesis, The University of Tennessee, Knoxville, Tenn.

Moody, F.H., J.B. Wilkerson, W.E. Hart, J.E. Goodwin, and P.A. Funk.  2000.  Non-intrusive flow rate sensor for harvester and gin applications.  In Proc. Beltwide Cotton Conf., 410-415. San Antonio, Tex.  4-8 January.  Memphis, Tenn.:  National Cotton Council.

Myers, A. 2000. The Ag Leader Technology cotton yield monitor system. In Proc. Beltwide Cotton Conf., 90-93. San Antonio, Tex.  4-8 January.  Memphis, Tenn.:  National Cotton Council.

Wilkerson, J. B., J. S. Kirby, W. E. Hart, and A. R. Womac. 1994. Real-time cotton flow sensor. ASAE Paper No. 941054. St. Joseph, Mich.: ASAE.

Wilkerson, J. B., F. H. Moody, and W. E. Hart.  2001.  Development and evaluation of a flow measurement device for cotton yield mapping.  ASAE Paper No. 01-1172.  St. Joseph, Mich.:  ASAE.

Wilkerson, J. B., F. H. Moody, W. E. Hart, and P. A. Funk. 2001. Design and evaluation of a cotton flow rate sensor. Trans. ASAE 44(6):  1415-1420.

Wilkerson, J. B., F. H. Moody, and J. S. Kirby. 1999. Real time volumetric flow sensor. U.S. Patent No. 5,920,018.

Wilkerson, J.B., F.H. Moody, and W.E. Hart.  2002.  Implementation and field evaluation of a cotton yield monitor.  Applied Engineering in Agriculture 18(2): 153-159.

Cotton Incorporated  

Ag Leader Technology

J.I. Case Corporation

John Wilkerson, Ph.D. 
The University of Tennessee
2506 E. J. Chapman Drive
Knoxville, TN  37996-4531
PHONE:  (865) 974-7266
wilkerj@utk.edu