| 摘要 |
PURPOSE: To detect head cloggings by comparing the difference between signals to be detected with two rotary magnetic heads with prescribed values to dispense with a reference voltage preparing circuit and a voltage comparator. CONSTITUTION: Envelope detection outputs are inputted to a microcomputer 7 to be converted into digital values. At this time, the sum of A/D conversion values is calculated and mean values VA, VB of envelope detection values of heads A, B are calculated. Next, a difference|VA-VB|is calculated to be compared with a preset reference value VC. Then, when|VA-VB|exceeds the VC, the computer judges that a clogging is caused in the head of one side to instruct a warning display. Moreover, a mean value (VA+VB)/2 of the detection outputs of heads A, B is compared with a prescribed reference value VD and when (VA+VB)/2 does not exceed the value VD, the computer judges that both heads are in clogging states to instruct the warning display. Further, information of cloggings of both heads, or the like are stored in the RAM in the computer 7.
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