The infl uence of bulk density of wheat grain on the accuracy of moisture measuring by the microwave method

The effect of the density of wheat grain on the accuracy of measuring its moisture content by the ultra-high frequency method is considered. The method is based on amplitude dielectric metrology, in which the attenuation of an electromagnetic wave passing through the grain is analyzed. A single-parameter moisture meter operating at ultra-high frequencies and intended for use in grain processing production has been developed. The structural diagram of the moisture meter and the principles of its operation are presented The device's design incorporates a mathematical model that takes into account the electrophysical properties of grain material and its interaction with ultra-high frequency radiation at a fixed frequency. A prototype of the device has been manufactured and tested in real production conditions. Grain with different densities, such as 87, 116, and 145 kg/m3, has been investigated. It has been experimentally established that as the grain density decreases, the relative error in measuring its moisture content increases, especially at high moisture contents exceeding 14 %. At a moisture content of 18 % and a grain density of 145 and 87 kg/m3, the relative error in measurement was 9.8 % and 44.7 %, respectively. The calculated partial derivatives of the signal amplitude with respect to density are significantly higher in conditions of high humidity, which indicates a strong dependence of the moisture meter readings on the density of the material in these conditions: even a small change in density can significantly increase the measurement error at high humidity. Graphs of the moisture meter signal amplitude dependence on humidity at different values of density and the results of regression analysis confirming the need to take into account the density during the instrument calibration are presented. The absolute and relative errors of moisture measurement are estimated depending on the sample density. The results of the studies confirm the effectiveness of the ultra-high frequency method of rapid moisture assessment and the developed moisture meter, provided that the infl uence of density is corrected.

1. Kovaleva A. A., Saitov R. I., Zaporozhets A. S., Parfenova E. G. Calibration methods for serial microwave moisture meters. Measurement Techniques, 60(3), 305–308 (2017). https://doi.org/10.1007/s11018-017-1191-6

2. Kalandarov P. I. Estimate of precision of thermogravimetric method of measuring moisture content: estimate of precision and effectiveness gained with the use of the method in the agro-industrial complex. Measurement Techniques, 64(6), 522–528 (2021). https://doi.org/10.1007/s11018-021-01963-9

3. Nelson S . O., Trabelsi S. Grain and seed moisture and density measurement through sensing of dielectric properties. Transactions of the ASAE, 53(2), 405–412 (2010). https://doi.org/10.13031/2013.29637

4. Fedotkin I. M., Klochkov V. P. Physico-technical fundamentals of moisture measurement in the food industry. Technika, Moscow (1974). (In Russ.)

5. Makhmudov M. I. Microprocessor-based microwave device for measuring grain moisture: abstract of the dissertation of the Candidate of Technical Sciences. Tashkent State Technical University named after Islam Karimov, Tashkent (2000).

6. Kalandarov P. I., Ikramov G. I. Evaluation of the effi ciency of an information and measuring system for monitoring the temperature and humidity of grain products. Measurement Techniques, 66(4), 237–243 (2023). https://doi.org/10.1007/s11018-023-02216-7

7. Iskandarovich K. P., Mamurovich M. Z., Egambergonovich A. N., Ugli A. H. H. Information and measurement control systems for technological processes in the grain processing industry. International Conference on Information Science and Communications Technologies (ICISCT 2021), pp. 500–504. https://doi.org/10.1109/ICISCT52966.2021.9670425

8. Kalandarov P. I. High-frequency moisture meter for measuring the moisture content of grain and grain products. Measurem ent Techniques, 65(4), 297–303 (2022). https://doi.org/10.1007/s11018-022-02082-9

9. Abdykadyrov A. A., Kalandarov P. I., Ikramov G. I., Kuttybaeva A. Y. Automatic ultra-high frequency moisture meter for solid dispersed materials. Utility model KZ 9170 (2024).

10. Smirnova V. V., Sidelnikova N. A., Maslovskaya N. A., Perepelitsa Yu. S. Assessment of the technological properties of wheat grain. Chief Agronomist, (9) (2020). (In Russ.)

11. Trukhachev V. I., Kiryushin V. I. Methods and means of grain quality control. Lan, St. Petersburg (2011). (In Russ.)

12. Issa S., Boussetta N. Infl uence of bulk density and moisture on the dielectric properties of cereals in RF and microwave ranges. Journal of Food Engineering, 97(3), 404–413 (2010). https://doi.org/10.1016/j.jfoodeng.2009.10.029

13. Atalay Kocakusak, Bektas Colak, Selcuk Helhel. Frequency dependent complex dielectric permittivity of rubber and magnolia leaves and leaf water content relation. Journal of Microwave Power and Electromagnetic Energy, 50(4), 294–307 (2016). https://doi.org/10.1080/08327823.2004.11688507

14. Kovaleva A. A., Saitov R. I., Zaporozhets A. S., et al. Microwave moisture meter for cereal grains. Measurement Techniques, 59(10), 1056–1060 (2017). https://doi.org/10.1007/s11018-017-1091-9

15. Lisovsky V. V., Bulko M. I. Automatic moisture control of agricultural materials by the microwave acoustic method. Energy saving is the most important condition for the innovative development of agriculture: materials of the International Scientifi c and Technical Conference, Minsk, November 23–24, 2017, BGATU, Minsk, p. 330–334 (2017). (In Russ.) https://rep.bsatu.by/handle/doc/2033

16. Saitov R.I., Abdeev R.G., Shvetsov M. V., Khasanova A.F., Abdeev E.R., Handmoynikov A.A. Mathematical model of the electromagnetic heating process of a multiphase multicomponent heavy oil reservoir. Bulletin of the Academy of Sciences of the Republic of Belarus, 29(4(92)), 73–79 (2018). (In Russ .) https://doi.org/10.24411/2076-4766-2017-10408

17. Tiwari G., Wang S. Design and modeling of radio frequency (RF) heating systems for food processing. Food Science and Technology International, 15(5), 437–448 (2009).

18. Lisovsky V. V. Microwave methods and devices for accurate moisture measurement in sugar beet production. Stiinta Agricola, 26(2), 55–59 (2017). (In Russ.) https://elibrary.ru/msolhh

19. Hammud F. M., Gerasimov V. P., Gordienko Yu. E. Microwave dielectric constant of dispersed moisture-containing media. Radiophysics and Radio Electronics, 10(3), 334–340 (2005). (In Russ.)

20. Ikramov G. I., Kalandarov P. I. Measurement of grain and grain products moisture content by ultrahigh-frequency method: infl uence of grain density inhomogeneity on the mass ratio of moisture. Measurement Techniques, 65(9), 695–701 (2022). https://doi.org/10.1007/s11018-023-02141-9