Method and apparatus for increasing throughput on disk drive quality control testing

An apparatus for increasing throughput for testing systems for defects in rotating disk bulk storage magnetic memories said testing system having a read head and read circuitry comprising:

• an input port for receiving an output signal from said read circuitry;
• delay means having an input coupled to said input port and having an output, for delaying the signal received at said input for a time equal to an integer multiple of the period of said signal received at said input and for presenting said delayed signal at said output;
• difference means having an output having a first input coupled to said output of said delay means and having a second input coupled to said input port, for detecting the difference in amplitude between the signals at said first and second inputs and for generating a signal at said output which is proportional to said difference;
• and
• comparator means having an output and having a first input coupled to said output of said difference means and having a second input coupled to a port for receiving a reference potential for comparing the signal at said first input to said reference potential and for generating a signal at said output when the signal at said first input exceeds said reference potential.

A method for increasing the throughput of quality control testing of disk drives comprising:

• delaying a periodic input signal indicative of the magnetic transitions of recorded test data by an interval equal to one period of said input signal;
• subtracting said delayed input signal from said input signal to determine the difference amplitude between these two signals;
• and
• comparing said difference amplitude to a predetermined threshold.

An apparatus for testing disk drives comprising:

• means for delaying a periodic input signal for an interval equal to one period of the input signal;
• means for subtracting said delayed input signal from said input signal to generate a difference signal;
• means for comparing said difference signal to positive and negative threshold values;
• and
• means for simultaneously comparing said input signal to a threshold during a predetermined time interval.