| 摘要 |
PURPOSE:To detect the quantity of wear and to discriminate the use limit due to wear without manual operation, by detecting the quantity of wear on the basis of the length of the time which is elapsed until the head terminal voltage exceeds a certain threshold when a magnetic head is driven by voltage. CONSTITUTION:Write data (a) is converted to magnetic head driving voltages (b) and (c) by a voltage driving circuit 1 to drive a magnetic head 4 through resistors 2 and 3. A head terminal voltage (f) is compared with a threshold voltage V1, and an output (g) is converted to a pulse (h) having the width of a time T1, which is elapsed until the terminal voltage (f) exceeds the threshold voltage V1, through a one-shot circuit 9. When this pulse (h) is inputted to a D type flip-flop 11, the state of the output (h) is latched by the trailing edge of an output (g) of a comparing circuit 8 because the output obtained by allowing the output (g) to pass through an inverter circuit 10 is inputted to the CP input terminal of the flip-flop 11, and thus, a wear detection output (i) is generated. |
