| 摘要 |
<p>PURPOSE:To exactly detect a dewing state by providing a sensor on a surface part of a rotary cylinder, and fetching a dewing detecting signal through a rotary transformer. CONSTITUTION:An AC signal generated by a transmitting circuit 6 passes through a rotary transformer 5 and applied to a dewing sensor 1. This AC signal is brought to voltage division into v1 and v2 in the ratio determined by an impedance portion of the transformer 5 and a resistance value of a resistor 7. This divided voltage v1 is rectified by a rectifying diode 8 and a capacitor 9, and inputted to a voltage comparator 12. In this case, the sensor 1 is dewed as soon as a cylinder 3 is dewed, and its resistance value is varied greatly, comparing with the time of drying. Subsequently, the divided voltage v2 is also varied, its variation is detected by comparing it with the normal time by the comparator 12, and a dewing protecting device is operated through a microprocessor 13, and loading of a magnetic tape is inhibited. The sensor 1 is in a dewing state for the same period as that of the cylinder 3, therefore, a malfunction caused by drying first is eliminated, and the dewing state can be detected exactly.</p> |
