A technique particularly useful for measuring the flying characteristics of a magnetic recording head on an air bearing adjacent a rotating disk is described. According to this technique one of a plurality of magnetic transducers mounted in the moving disk records a line of signals of known amplitude and wavelength on a magnetic recording surface placed on the recording head being evaluated. The signal amplitude is read from this line of recorded signals as the disk rotates, and the relative spacing between the head and disk at two points on the head is determined from the relative amplitudes of the signals from the two points. In this way, the pitch, roll and deformation of the recording head can be measured in a dynamic situation.
A tester which can measure both the air bearing thickness and the dynamic electrical characteristics of a head gimbal assembly (HGA) of a hard disk drive. The tester has a disk that is rotated by a spindle motor. The disk has a transparent portion that is used to measure the air bearing thickness and a magnetic portion that used to measure the electrical characteristics. The HGA is moved adjacent to the transparent and magnetic portions by a loader mechanism. The HGA is separated from the rotating disk by an air bearing. The tester has an optical system which measures the thickness of the air bearing when the HGA is adjacent to the transparent portion of the disk. The tester also has an electrical tester which measures the electrical characteristics when the HGA is adjacent to the magnetic portion. The loader mechanism moves the HGA between the transparent and magnetic portions so that the air bearing thickness and the electrical characteristics of an HGA can be measured in the same tester.
A read-write head is provided with a plurality of piezoelectric transducers which produce signals related to its movement as it flies over an adjacently rotating recording disk. By filtering these signals to determine their spectral components in low, medium and high ranges, hard contacts between the head and disk, disk wear or roughness and head movement can be determined.
An improved method and apparatus for monitoring the thickness of a film includes a sensor roll which cooperates with a compliant roll to form a nip through which the film passes. As the two rolls rotate relative to each other, magnets disposed in the sensor roll are sequentially moved to and from the nip. As a magnet moves by the nip, the field emanating from the magnet is concentrated by a body of material having a relatively high magnetic permeability and disposed in the compliant roll. This results in an induced voltage being generated in a sensor coil. The output from the sensor coil is transmitted to control circuitry which effects operation of a suitable apparatus to control the thickness of the film.
Surface relief analyzing equipment comprises a turntable and an audio frequency pick-up including a stylus. A substrate bearing the surface relief is rotated on the turntable at a fixed frequency and and analogue electrical signal produced at a pick-up transducer is passed through an a-d converter. Digital data is processed to produce an input to a display for registering a pictorial representation of the surface relief.
An improved method and apparatus for monitoring the thickness of a film includes a sensor roll which cooperates with a compliant roll to form a nip through which the film passes. As the two rolls rotate relative to each other, magnets disposed in the sensor roll are sequentially moved to and from the nip. As a magnet moves by the nip, the field emanating from the magnet is concentrated by a body of material having a relatively high magnetic permeability and disposed in the compliant roll. This results in an induced voltage being generated in a sensor coil. The output from the sensor coil is transmitted to control circuitry which effects operation of a suitable apparatus to control the thickness of the film.
