| 摘要 |
PURPOSE:To reduce the occurrence of a malfunction due to leakage resistance produced between a cathode electrode and a guard electrode and to improve reliability, by a method wherein the voltage of the guard electrode is equalized with a return voltage of an amplifying circuit. CONSTITUTION:A voltage of a load resistance R1, connected in series to a cathode electrode 2 and an anode electrode 3, is amplified (5), and an amplifying output voltage is divided to return it to an amplifying circuit 5. The divided voltage is inputted to a guard electrode 8 located between the electrodes 2 and 3. This permits the reduction of a malfunction due to a leakage resistance R4 produced between the electrodes 2 and 3 owing to deterioration in insulation of an electrode retainer, contamination by smoke, and foreign matters such as dusts. |
