Feasibility of measurement of the dielectric properties for bulk density and moisture-content
determination in cereal grain and oilseed with inexpensive microstrip antennas in the near
field is discussed. Results obtained for wheat and soybeans with a pair of single-patch
microstrip antennas operating at 5.8GHz and 24C are compared to those taken in the
far field with a pair of focused-beam horn=lens antennas. The standard errors of calibration
calculated for bulk density and moisture-content prediction from measurement of the
dielectric properties in the near field are slightly higher than those corresponding to far-field
measurements but remain within an acceptable error range.
1. E. Nyfors and P. Vainikainen. Industrial Microwave Sensors. Artech House, Norwood, MA (1989).
2. A. Kraszewski. Microwave Aquametry. IEEE Press, Piscataway, NJ (1996).
3. A. W. Kraszewski and S. Kulinski. An improved microwave method of moisture content measurement
and control. IEEE Transactions on Industrial Electronics and Control Instrumentation 23:364–370
(1976).
4. W. Meyer and W. Schilz. Feasibility study of density-independent moisture measurement with
microwaves. IEEE Transactions on Microwave Theory and Techniques 29:732–739 (1981).
5. F. Menke and R. Knochel. New density-independent moisture measurement methods using frequencyswept
microwave transmission. IEEE MTT-S Symposium, vol. 3, pp. 1415–1418. The Institute of
Electrical and Electronics Engineers, Inc., Piscataway, NJ (1996).
6. S. Trabelsi, A. Kraszewski, and S. O. Nelson. Simultaneous determination of density and water content
of particulate materials by microwave sensors. Electronics Letters 33:874–876 (1997).
7. S. Trabelsi, A. Kraszewski, and S. Nelson. Method for Simultaneous and Independent Determination
of Moisture Content and Density of Particulate Materials from Radio-Frequency Permittivity Measurements,
U.S. Patent Number 6,147,503, 2000.
8. S. Trabelsi and S. Nelson. Dielectric methods for multiparameter microwave sensor. Proceedings of
the 5th International Conference on Electromagnetic Wave Interaction with Water and Moist
Substance, pp. 56–63. Industrial Research Limited, Auckland, New Zealand (2003).
9. S. Trabelsi, A. W. Kraszewski, and S. O. Nelson. Unified calibration method for nondestructive
dielectric sensing of moisture content in granular materials. Electronics Letters 35:1346–1347 (1999).
10. S. Trabelsi, A. Kraszewski, and S. O. Nelson. New calibration technique for microwave moisture
sensors. IEEE Transactions on Instrumentation and Measurement 50:877–881 (2001).
11. A. Sihvola. Electromagnetic Mixing Formulas and Applications. Institution of Electrical Engineers,
London, UK (1999).
12. D. D. Archibald, S. Trabelsi, A. W. Kraszewski, and S. O. Nelson. Regression analysis of microwave
spectra for temperature-compensated and density-independent determination of wheat moisture
content. Applied Spectroscopy 52:1435–1446 (1998).
13. P. G. Bartley, Jr., R. W. McClendon, S. O. Nelson, and S. Trabelsi. Determining moisture content of
wheat with an artificial neural network from microwave transmission measurements. IEEE Transactions
on Instrumenation and Measurement 47:123–125 (1998).
14. S. Trabelsi, A. Kraszewski, and S. Nelson. Universal Dielectric Calibration Method and Apparatus for
Moisture Content Determination in Particulate and Granular Materials, U.S. Patent No. 6, 691, 563,
2004.
15. F. Volgy, J. Burrows, and R. Shepherdson. Calibration methods for non-density-sensitive microwavebased
moisture sensors. Papers from the 4th International Symposium on Humidity and Moisture,
pp. 371–378. Center of Measurement Standards, ITRI, and National Measurement Laboratory
R.O.C., Taiwan, R.O.C. (2002).
16. K. J. Bois, A. D. Benally, P. S. Nowak, and R. Zoughi. Cure-state monitoring and water-to-cement ratio
determination of fresh portland cement—based materials using near field microwave techniques.
IEEE Transactions on Instrumenation and Measurement 47:628–637 (1998).
17. ASAE. ASAE S352.2 Moisture measurement—Unground Grain and Seeds, in ASAE Standards 2000,
p. 563. American Society of Agricultural Engineers, St Joseph, MI (2000).
18. H. E. Bussey. Measurement of the RF properties of materials—A survey. Proceedings of the IEEE
55:1046–1053 (1967).
19. S. Trabelsi and S. O. Nelson. Free-space measurement of dielectric properties of cereal grain and
oilseed at microwave frequencies. Measurement Science and Technology 14:589–600 (2003).
20. S. Trabelsi and S. O. Nelson. Calibration Methods for Multiparameter Microwave Sensors, IEEE
IMTC=2003 Tutorial Program, May 19, 2003, Vail, Colorado, USA, 2003.
21. S. Trabelsi, A. W. Kraszewski, and S. O. Nelson. Phase-shift ambiguity in microwave
dielectric properties measurements. IEEE Transactions on Instrumentation and Measurement 49:
56–60 (2000).
22. R. Garg, P. Bhartia, I. Bahl, and A. Ittipiboon. Microstrip Antenna Design Handbook. Artech House,
Norwood, MA, 2001.
23. F. Volgyi. Integrated Microwave Moisture Sensors for Automatic Process Control. In Microwave
Aquametry, Emerging Technologies, A. Kraszewski (ed.), pp. 223–238 (1996). IEEE Press,
Piscataway, NJ.
24. A. W. Kraszewski. Microwave aquametry—needs and perspectives. IEEE Transactions on Microwave
Theory and Techniques 39:828–835 (1991).