Ratio method for measurement of MR read head resistance

A system for measuring the resistance of a magnetoresistive head, comprising:

• circuitry for generating an adjustable bias current;
• a magnetoresistive head connected to selectively receive the bias current, the bias current producing a head voltage across the magnetoresistive head;
• a reference load connected to selectively receive the bias current, the bias current producing a reference voltage across the reference load;
• and
• circuitry for measuring the reference voltage and the head voltage,
• wherein the reference voltage is used determine the resistance of the magnetoresistive head, based on the bias current and the head voltage.

A magnetic storage/read system comprising:

• a recording medium for magnetically storing a signal;
• a magnetoresistive element connected to read from and write to the recording medium;
• and
• a circuit for determining the resistance across the magnetoresistive element, having
• a circuitry for generating an adjustable bias current which is selectively passed through the magnetoresistive element to produce a head voltage across the magnetoresistive element;
• a reference load connected to selectively receive the bias current, the bias current producing a reference voltage across the reference load;
• and
• circuitry for measuring the reference voltage and the head voltage,
• wherein the reference voltage is used determine the resistance of the magnetoresistive element, based on the bias current and the head voltage.

A disk drive unit comprising:

• a controller unit;
• a spindle drive controller coupled to the controller unit;
• a plurality of stacked magnetic disks rotatably mounted on a spindle coupled to a spindle motor, said spindle motor electrically coupled to the spindle drive controller;
• at least one magnetoresistive (MR) head electrically coupled to the controller unit;
• an actuator drive controller coupled to the controller unit;
• an actuator shaft rotatably coupled to an actuator motor, said actuator motor coupled to the actuator drive controller;
• an actuator assembly coupled to the actuator shaft, comprising
• a comb unit having a plurality of actuator arms and a hub assembly coupled to the actuator shaft, and
• a plurality of head suspension assemblies each coupled to one of said plurality of actuator arms, each head suspension assembly comprising an MR head, and
• an arm electronics unit situated in close proximity to said actuator assembly, comprising a control unit for supplying a measurement enable signal;
• and
• a measurement circuit implemented within said arm electronics unit, comprising
• a circuitry for generating an adjustable bias current which is selectively passed through the magnetoresistive element to produce a head voltage across the MR head;
• a reference load connected to selectively receive the bias current, the bias current producing a reference voltage across the reference load;
• and
• circuitry for measuring the reference voltage and the head voltage,
• wherein the reference voltage is used determine the resistance of the MR head, based on the bias current and the head voltage.