| 摘要 |
PROBLEM TO BE SOLVED: To prevent the contamination of an electrode by a simple mechanism requiring no energy such as power in driving by gathering a contaminant in water by separately providing an electrode not participated in measurement. SOLUTION: Other than a first electrode 1 becoming an anode and a second electrode 2 becoming a cathode, a third electrode 3 of which the standard electrode potential is lower than that of the second electrode 2 becoming the cathode is provided in a state capable of being immersed in a sample. At a time of measurement, the second electrode 2 is connected to the first electrode 1 through a measuring system and, at a time of non-measurement, a changeover means for connecting the second and third electrodes is provided. By this constitution, the second electrode 2 set to the cathode at a time of measurement becomes an anode and the third electrode 3 becomes a cathode at a time of non-measurement. Usually, the contamination of the cathode is marked as compared with the anode not almost contaminated but, by allowing the second electrode 2 to function as the anode at a time of non-measurement, the adhesion of a contaminant to the second electrode can be prevented. |
