In situ sensor based contact detection

An apparatus comprising:

• a recording medium;
• a transducer adjacent the recording medium, wherein the transducer comprises a writer, a reader, a heater, and a thermally responsive sensor;
• and
• a control circuit coupled to the transducer and adapted to:
• apply power to the heater to establish a fly height of the transducer;
• supply a bias current through the thermally responsive sensor to generate a bias signal;
• measure a root mean square (RMS) voltage VRMS of the thermally responsive sensor based on the bias signal;
• determine a threshold voltage VT;
• and
• detect a contact event between the transducer and the medium based on VRMS being greater than VT.

A system comprising:

• a recording medium adapted for rotation about a central axis, the recording medium storing a plurality of spaced apart servo wedges that define tracks adapted to store data in data sectors between adjacent pairs of the servo wedges;
• a transducer adjacent the recording medium comprising a writer adapted to store data to the data sectors, a reader adapted to read back the data stored to the data sectors and to read back servo data from the servo wedges, a write heater adapted to lower a fly height distance between the writer and the medium responsive to an applied write heater value, a read heater adapted to lower a fly height distance between the reader and the medium responsive to an applied read heater value, and at least one thermally responsive sensor;
• and
• a preamplifier circuit adapted to, during a write operation:
• apply write signals to the writer to write data to a selected track;
• apply the write heater value to the write heater to establish a first fly height distance for the writer;
• apply a bias current to the thermally responsive sensor;
• measure a root mean square (RMS) voltage VRMS of the thermally responsive sensor based on the bias signal;
• determine a threshold voltage VT;
• and
• detect a contact event between the transducer and the medium based on VRMS being greater than VT.