ARS | Publication request: Integrating an Embedded System within a Microwave Moisture Meter

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Proceedings
Publication Acceptance Date: June 21, 2011
Publication Date: August 7, 2011
Citation: Trabelsi, S., Lewis, M. 2011. Integrating an Embedded System within a Microwave Moisture Meter. American Society of Agricultural and Biological Engineers. ASABE Paper No.1110943.

Interpretive Summary: Moisture content of grain and seed must be determined whenever it is traded. If the moisture content is too high for safe storage, it must be dried, and costs of drying must be taken into account in determining the fair price. Because research has discovered important advantages of using microwave frequencies for sensing grain and seed moisture content, a microwave moisture meter has been built and field-tested successfully. However, this moisture meter prototype required a laptop computer to control and provide the moisture content of grain and seed samples tested. This paper describes a microcontroller and embedded system to replace the laptop computer and provide a user interface for input and output information, event execution, process control, and data storage. Initial testing shows that the moisture meter with the new embedded system maintains the performance and accuracy observed in the original laptop-copmputer-controlled meter. This development resulted in a complete microwave moisture meter, with keypad input and liquid crystal display, which has improved reliability and portability and lower cost, making it more attractive for commercial development. Availability of such improved moisture meters will result in better management of grain and seed commodities and consequent benefits for growers, handlers, processors, and consumers.

Technical Abstract: In this paper, the conversion of a PC or laptop-controlled microwave moisture meter to a stand-alone meter hosting its own embedded system is discussed. The moisture meter uses low-power microwaves to measure the attenuation and phase shift of the sample, from which the dielectric properties are calculated. The dielectric properties are then used to determine instantaneously and nondestructively the moisture content in the grain or seed sample. The previous system consisted of the moisture meter being controlled via USB interface by an external laptop or PC. Though effective, the system lacked full portability and was susceptible to laptop crashes and interruptions in communication between the meter and laptop. To improve the system, a microcontroller was selected in the design of an embedded system for the moisture meter. The microcontroller provides a graphical 144 x 32 pixel LCD and 16-button keypad to facilitate user interaction. The embedded system provides the following functionalities: user interface (input/output), event execution, process control, data acquisition, and data storage. Initial testing shows that the moisture meter with the new embedded system maintains the performance and accuracy observed in the original PC or laptop controlled meter. The integration of the embedded system with the microwave moisture meter provides a cost-effective, portable, and robust solution for microwave moisture sensing.