| 摘要 |
PURPOSE:To use an oxygen electrode for a long time over a wide range of concns. by controlling the overcurrent of the electrode and changing the thickness of the gas permeation membrane in accordance with the concn. CONSTITUTION:A voltage is supplied to the oxygen electrode 1 from the power source part 3 of an oxygen electrode control part 2, and a current is outputted from the electrode 1. Since the output current is feeble, the output current of the electrode 1 is converted into a voltage by a current-voltage converter part 4 at a magnification of 10<6>-10<7>V/A and outputted. The output at the converter part 4 is monitored by an output current comparator part 5, and the voltage of the power source part 3 is lowered when the output exceeds a set value to keep the output current constant. Furthermore, an oxygen electrode having a thin gas permeation membrane is prepared to measure the oxygen concn. in the low-concn. region, and the oxygen electrode having a thick oxygen permeation membrane is prepared to measure the oxygen concn. in the high- concn. region. Consequently, the maximum output current of the oxygen electrode is limited, the consumption of the anode and electrolyte is controlled, the measuring range is widened, and the service life of the electrode is prolonged. |
