Spin valve sensors

This paper demonstrates spin valve sensor applications as read elements in storage systems, or, when in a Wheatstone bridge configuration, as rotation al speed control devices (for ABS systems), high current monitoring devices for power lines, and positioning control devices in robotic systems. For r ecording heads, shielded spin valve sensors are adequate for high linear de nsity recording, A tape head was fabricated with output 400 mu V per micron of trackwidth, with a D50 value of 100 kfci, and signal lass of -0.34 dB/k fci, For rotational speed measurement, spin valve bridge sensors with flux guides were used, yielding a 400-mVpp amplitude, and square wave output wit h rise/fall times below 70 mu s, when excited by a magnetized wheel. Amplit ude is independent of speed (0-3000 rpm), and of sensor to wheel separation (0.5-2.0 mm). For power line applications, currents up to 2100 A. (at 50 H z) could be measured with a sensitivity of 35 mu Vrms/A and deviations from linearity of +/- 1.5%, In robot position control, a maximum error of +/- 9 mu m over a +/- 0.5-mm span was obtained. In the two last cases, bridges w ithout flux guides are used to maximize linear response. (C) 2000 Elsevier Science S.A. All rights reserved.