Method and apparatus for determining separation between read and write elements of a transducer

DETAILED DESCRIPTION In accordance with the invention there is provided, a method for determining separation between a read element and a write element of a head in a direct access storage device having a rotating disk.
The method comprises the steps of determining a first read to write time delay with the head positioned at a first radius of the disk; determining a second read to write time delay with the head positioned at a second radius of the disk and computing the separation between the read element and the write element based on a difference between said first delay and said second delay, and speed of rotation of the disk.
At least one of said steps of determining read to write time delay comprises the steps of writing a first trigger pattern with a write element; writing a second trigger pattern a nominal time T after triggering on said first trigger pattern; measuring the time interval between said first and said second trigger patterns; and computing a difference between said interval and the nominal time T.
The delays are a function of skew angle between the head and the moving disk, and skew angle is also used in said step of computing.
The method further comprising the steps of: computing delay times resulting from skew for successive radial positions of the head with respect to the disk as a function of said separation, the skew angle, and the rotational speed of the disk, and using said delay times to correct positioning of trigger patterns as a servo pattern is written on the disk.
The invention is also directed to a method for determining a value for systematic errors in the placement of data on a rotating storage medium by a head having separate read and write elements, said errors being due to geometric misalignment of said read element and said write element.
The method comprising the steps of: measuring a first time interval between trigger patterns which are written with the head located at a given radial position on said disk, measuring a second time interval between a pair of trigger patterns the first of which is written with the head located at a first radial position the second of which is written with the head located at a second radial position, said first and second radial positions being separated by a distance sufficiently small to allow both first and second trigger patterns to be read by the head placed at a single radial position and sufficiently large to observe said systematic error