| 摘要 |
PURPOSE:To detect accurately a time point at an instant when a coating film is broken, by using a big difference created in a resistance value between a substrate and a head depending upon whether a magnetic layer is present on the substrate or not. CONSTITUTION:A resistor 2 is connected with a head arm 1, an electrical voltage is applied between another and of this resistor 2, and a spindle 3 and recorder are connected with both ends of the resistor 2. When a coating film remains not broken, no current is allowed between head 1 and spindle 3 and so, no voltage is produced on both ends of the resistor 2. Upon breakage of the film, the current is admitted for generation of voltages, (V) on both ends of the resistor 2. For instance, the applied voltage E is of 10V and resistor R of 43KOMEGA, a shown voltage change is observed. By detecting the voltage change on both ends of the resistor 2 with a differentiating circuit etc., the very instant D of the coating film can be defected.
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