An undergraduate laboratory in magnetic recording fundamentals

An undergraduate course in data storage systems has recently been augmented with several laboratory experiments designed to enrich the students’ understanding of magnetic hysteresis, magnetic sensors, and storage systems. In this paper, the three devices that have been designed for such experiments will be described. Each device is conceptually simple and is easily replicated using inexpensive, off-the-shelf electronics. One device demonstrates the concept of magnetic hysteresis, displaying for students the hysteresis loop, including minor loops, of a toroid. A second device contrasts inductive and magnetoresistive readback techniques, illustrates the effects of velocity on each type of sensor, and shows the need for bias in magnetoresistive sensing to obtain a linear readback response. The last device, a modified version of the well-known audiotape recorder, provides a hands-on implementation of a simple magnetic recording system. Students can write, read, and analyze data to view the effects of frequency roll-off and write-saturation, and parameters such as PW50 and D50. Using a variety of tape materials in the collection of the experimental data, students can compare the properties of varying types of media.