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Session 1264

COMPUTER INTERFACING A MICROWAVE SPECTROMETER: AN EDUCATIONAL APPROACH

B. F. Draayer, J. N. Dahiya Physics Department Southeast Missouri State University Cape Girardeau, MO 63701

ABSTRACT

A laboratory procedure for introducing undergraduate students to the principles of analog to digital converters is described. The procedure involves interfacing an analog to digital chip, the ADC 0804, to a PC via a cable connected to the PC's parallel port. Exploiting the parallel port minimizes equipment cost and is safer for the students and the computers. Evidence that students are in a position to understand and use interface equipment properly is provided by describing a technique to computerize a microwave spectrometer for the purpose of studying the dielectric behavior of materials. A cylindrical microwave resonant cavity in the TE011 mode is used as a probe for dielectric relaxation studies as a function of temperature. The computer interface allows a very precise measurement of the frequency shifts and Q-changes of the microwave signal as the material under investigation goes through a dielectric change. These values of the frequency shifts and Q-changes translate into the real and imaginary parts of the dielectric constant through the Slater’s perturbation equations.

INTRODUCTION

At Southeast Missouri State University, undergraduate research is an extremely important component to each student's education, especially with the current emphasis being placed on experiential learning. Southeast is primarily an undergraduate institution, and we rely heavily on undergraduate students to perform simple yet time-intensive research tasks. We have also been trying to automate the data collection process in many of our labs since powerful PCs are readily available even for poorly equipped lab rooms. However, it became evident to us that our students were lacking basic knowledge about A/D conversion when we asked them to design and build simple computer interfaces. A prime example of this occurred when we asked undergraduate students to build a temperature and frequency interface for a microwave spectrometer using off-the-shelf components. Students were unable to configure the equipment properly because they did not understand such terms as resolution, full-scale error, and step-size. To provide students with hands-on experience with A/D converters, we designed a laboratory procedure that allows the students to interface an A/D converter chip to a parallel port on a PC. The rest of this paper describes the microwave spectrometer alluded to earlier, the A/D parallel port laboratory procedure we developed, and the final interface design for the microwave spectrometer.

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Dahiya, J. N., & Draayer, B. F. (1998, June), Computer Interfacing A Microwave Spectrometer: An Educational Approach Paper presented at 1998 Annual Conference, Seattle, Washington. 10.18260/1-2--6974