Noise detecting apparatus for magnetic heads

An apparatus for testing magnetic heads comprising:

• an amplifier circuit having a variable gain, an input circuit and an output circuit;
• digital-to-analog converting means connected to said variable gain of said amplifier circuit;
• a head receiving input means for receiving a magnetic head;
• a mode select circuit electrically disposed between said head receiving input means and the input circuit of said amplifier circuit;
• a clamping circuit disposed between said mode select circuit and said amplifier circuit;
• a detector circuit electrically connected to the output circuit of said amplifier circuit;
• and
• a timing control circuit electrically coupled to said mode select circuit for generating a writing cycle, a reading cycle and a clamping cycle;
• wherein said apparatus is characterized by a writing model a reading mode and a clamping mode between said writing and reading modes, such that during said writing mode said timing control circuit generates said writing cycle which activates said mode select circuit, thereby allowing electrical signal to be written into the magnetic head, and when operating from said writing mode to said clamping mode, said timing control circuit generates a clamping cycle, so that spurious noise occurring during said clamping cycle is bypassed by said clamping circuit and prevented from being detected as a noise event, and when operating from said clamping mode to said reading mode, the electrical signal induces electrical noise in the magnetic head, so that during said reading mode said timing control circuit generates said reading cycle which activates said mode select circuit, thereby allowing the induced noise to pass through said amplifier circuit and be detected by said detector circuit as noise events in the magnetic head.

An apparatus for testing noise in a magnetic head comprising:

• an input circuit having an input port adapted for receiving the magnetic head;
• a mode select circuit electrically coupled to said input circuit;
• a timing control circuit electrically coupled to said mode select circuit for generating a writing cycle, a reading cycle and a clamping cycle;
• a pattern generator circuit electrically coupled to said input circuit for generating a predefined signal pattern;
• an amplifier circuit having a gain input connected to digital-to-analog controlled means, said amplifier circuit being coupled to said mode select circuit;
• and
• a detector circuit electrically connected to said amplifier circuit;
• wherein said apparatus is characterized by a writing mode, a clamping mode and a reading mode, such that during said writing mode, said timing control circuit generates said writing cycle which activates said mode select circuit and allows the predefined signal pattern to be written in the magnetic head, and such that during said clamping mode, said timing control circuit generates said clamping cycle which activates said mode select circuit to bypass and prevent noise induced in the magnetic head from passing through said detector circuit, and such that during said reading mode, said timing control circuit generates said reading cycle which activates said mode select circuit allowing noise induced by the predefined signal pattern written in the magnetic head during said writing cycle to pass through said detector circuit and be detected as noise events.

An apparatus for detecting noise in magnetic heads, said apparatus being characterized by a reading mode and a writing mode, comprising:

• an analog circuit portion including a head receiving input circuit for receiving a magnetic head, a detector circuit, and an amplifier circuit disposed between said head receiving input circuit and detector circuit, said amplifier circuit having a variable gain input;
• a digital circuit portion having a processor circuit, a counter circuit, a pattern generation circuit, and data buses electrically connecting said processor, counter and pattern generation circuits;
• a plurality of signal lines electrically connecting said analog circuit portion and said digital circuit portion, said plurality of signal lines including a first signal line electrically connecting said pattern generation circuit and said input circuit, and a second signal line electrically connecting said detector circuit and said counter circuit;
• and
• a reference voltage supply circuit which includes digital-to-analog converting means having an analog input and a digital input for receiving an input analog voltage level and an input digital signal, respectively, and an analog output electrically connected to said variable gain input of said amplifier circuit such that said analog output generates analog output voltage levels as fractions of the input analog voltage level in response to the input digital signal, thereby allowing the variable gain of said amplifier circuit to be digitally preset by said reference voltage supply circuit prior to noise detection;
• wherein during said writing mode, said processor circuit activates said data generation circuit allowing data to be written into the magnetic head via said input circuit through said first signal line, and operating from said writing mode to said reading mode electrical noise is induced in the magnetic head, such that during said reading mode, said processor circuit deactivates said data generation circuit allowing the induced electrical noise to pass through said amplifier circuit into said detector circuit, said detector circuit being electrically coupled to said counter circuit which registers the electrical noise as noise events in the magnetic head.