Automatic testing system for magnetoresistive heads

Abstract

A preprogrammed controller, preferably a stored program computer such as an IBM PC computer, is programmed to automatically control all the steps in the testing of a MR reproduce head. First, the magnitude of the sense current is established by command of the controller, and a voltage proportional to the sense current flowing in the head is monitored by the controller. An electromagnet, having high permeability pole pieces, and whose current is programmed by the controller provides a the magnetic field for exciting the MR head. The MR device is placed on an measured magnetic equipotential of the field of the electromagnet, and a Hall sensor magnetic detector is placed on the same magnetic equipotential line but in a different physical position from the MR device. The output of the Hall sensor is fed into the preamplifier electronics, digitized by a converter and this digital output is stored in the controller memory for future processing. Preamplifier electronics are also fed from the voltage output of the MR head, and the controller initiates a series of voltage measurements which are digitized and stored in the controller memory. By controlling the current to the electromagnet driver, the test field at the MR element is swept from a minimum field value to a maximum field value and back again, while correlated voltage data from the head is acquired.