| 摘要 |
PURPOSE:To distinguish the elements which are punctured during polarization treatment by connecting the piezoelectric elements to be polarized, a polarization protective resistance, a light emitting element and a current limitting resistance to a D.C. source and by connecting a varistor element and etc. in parallel to the light emitting element and the current limitting resistance. CONSTITUTION:A switch 5, a current limitting resistor 6, a LED7, a polarization protective resistor 8 and a direct circuit of the piezoelectric element 9 to be polarized are connected to a D.C. source 4. Then, a varistor element 10 is connected to the current limitting resistor 6 and the LED7 in parallel to them. Only the piezoelectric element part is immersed in a silicon oil constant temperature bath of 100 deg.C and a D.C. voltage of 10kV is applied to the whole part. In a normal state, the D.C. voltage of 10kV is entirely applied to the piezoelectric element 9. If the element is punctured, a resistance value of the piezoelectric element 9 decreases and a current of about 2mA flows. The both-side voltage of the current limitting resistor 6 and the LED7 is restrained to be about 100V by the varistor element 10 so that the current restrained to be 1mA by the resistor 6 flows in the LED7 to cause it to emit the light. |
