SENSING METHODS & INSTRUMENTATION FOR RAPID DETERMINATION OF MOISTURE CONTENT... AND OTHER QUALITY ATTRIBUTES OF GRAINS, SEEDS, & NUTS
Location: Quality and Safety Assessment Research Unit
Title: Embedded solution for a microwave moisture meter
Submitted to: Southeastcon, IEEE
Publication Type: Proceedings
Publication Acceptance Date: February 10, 2011
Publication Date: May 17, 2011
Citation: Trabelsi, S., Lewis, M. 2011. Embedded solution for a microwave moisture meter. Southeastcon, IEEE. 2011 CDROM.
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. 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.
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 is based on the free-space transmission measurement technique and uses low-intensity microwaves to measure the attenuation and phase shift of the sample, from which the dielectric properties are calculated. The dielectric properties are then used for instantaneous and nondestructive determination of the moisture content in the grain or seed sample. The previous system consisted of the moisture meter and measurement procedure being controlled via USB interface by an external laptop or PC. Though effective, the system lacked full portability and was susceptible to computer failure and interruptions in communication between the meter and computer. To improve the system, a microcontroller was selected in the design of an embedded system for the moisture meter, making it a stand-alone system. 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. The integration of the embedded system with the microwave meter provides a portable, robust, and cost-effective solution for microwave moisture sensing.