| 摘要 |
PURPOSE:To prevent the decrease in copying accuracy of a copying device for welding provided with a sensor utilizing high frequency current owing to a change in temp. by providing a variable capacity circuit and a correcting circuit for the purpose of correcting the malfunction of the sensor owing to the temp. change. CONSTITUTION:In a copying detector which supplies the high frequency current from an oscillating circuit 2 to a detecting coil 5 of a sensor 1, and detects the change in the current owing to a change in an inductance when the sensor 1 attaches and detaches to and from an object to be detected by means of a detecting circuit 8, micro DC current is supplied to the coil 5 to discover the abnormality such as overheating and disconnection of the detecting coil. In order to prevent the decrease in the copying detection accuracy owing to a rise in the temp. of the sensor 1, the change in the capacitance with a change in temp. is offset with a variable capacity circuit 11 provided with a threshold setting circuit 15 and a comparator 13. The conductance characteristic value of the detecting circuit by the change in temp. is corrected linearly with a correcting circuit 12 whereby the influence of temp. upon the detection accuracy of the copying detector is prevented. |
