Electrolyte concentration measuring apparatus and measuring method using same

1. An electrolyte concentration measuring apparatus comprising:

a plurality of ion selective electrodes and one reference electrode;

a sample introduction unit that introduces a sample solution into the plurality of ion selective electrodes and the reference electrode;

a potential measuring unit that measures a voltage between the plurality of ion selective electrodes and the reference electrode; and

a resistance measuring unit that measures a direct-current resistance of the plurality of ion selective electrodes, wherein the resistance measuring unit measures the direct-current resistance using two of the plurality of ion selective electrodes,

and wherein the resistance measuring unit corrects the direct-current resistance using an electromotive force of the ion selective electrodes themselves.

2. The electrolyte concentration measuring apparatus according to claim 1 , wherein the resistance measuring unit measures the direct-current resistance using one of the plurality of ion selective electrodes and the reference electrode.

3. The electrolyte concentration measuring apparatus according to claim 1 , wherein one of the two of the plurality of ion selective electrodes is an ion selective electrode having a resistance lower than a solution resistance between the ion selective electrode and the reference electrode, or an ion selective electrode based on an ion-exchange membrane.

4. The electrolyte concentration measuring apparatus according to claim 1 , wherein the resistance measuring unit measures the direct-current resistance using two of the plurality of ion selective electrodes and the reference electrode.

5. The electrolyte concentration measuring apparatus according to claim 1 , further comprising a measuring unit that serves as both the potential measuring unit for voltage measurement and the resistance measuring unit for direct-current resistance measurement.

6. The electrolyte concentration measuring apparatus according to claim 5 , wherein the resistance measuring unit includes:

a resistor connected between one of the plurality of ion selective electrodes and the reference electrode; and

a switch unit for connecting or disconnecting the resistance.

7. The electrolyte concentration measuring apparatus according to claim 5 , wherein the resistance measuring unit includes:

a resistor connected between two of the plurality of ion selective electrodes; and

a switch unit for connecting or disconnecting the resistance.

8. The electrolyte concentration measuring apparatus according to claim 1 , wherein:

the potential measuring unit measures an electromotive force between at least one of the plurality of ion selective electrodes and the reference electrode; and

the resistance measuring unit measures a voltage and a current between the at least one of the ion selective electrodes and the reference electrode, and determines the direct-current resistance from the electromotive force, the voltage, and the current.

9. The electrolyte concentration measuring apparatus according to claim 1 , wherein:

the potential measuring unit measures an electromotive force between at least one of the plurality of ion selective electrodes and the reference electrode; and

the resistance measuring unit measures a voltage and a current between two of the plurality of ion selective electrodes, and determines a sum of resistance values of the two ion selective electrodes from the electromotive force, the voltage, and the current as the direct-current resistance.

10. The electrolyte concentration measuring apparatus according to claim 6 , wherein:

the potential measuring unit measures a first electromotive force between at least one of the plurality of ion selective electrodes and the reference electrode;

the potential measuring unit measures a second electromotive force between the at least one ion selective electrode and the reference electrode with the at least one ion selective electrode and the reference electrode being connected by the resistor; and

the resistance measuring unit determines the direct-current resistance from the first electromotive force, the second electromotive force, and a resistance value of the resistor.

11. The electrolyte concentration measuring apparatus according to claim 7 , wherein:

the potential measuring unit measures a first electromotive force between a first ion selective electrode among the plurality of ion selective electrodes and the reference electrode, and a second electromotive force between a second ion selective electrode among the plurality of ion selective electrodes and the reference electrode;

the potential measuring unit measures, with the first ion selective electrode and the second ion selective electrode being connected by the resistor, a third electromotive force between the first ion selective electrode and the reference electrode, and a fourth electromotive force between the second ion selective electrode and the reference electrode; and

the resistance measuring unit determines, from the first electromotive force, the second electromotive force, the third electromotive force, the fourth electromotive force, and a resistance value of the resistor, a resistance value of the first ion selective electrode and a resistance value of the second ion selective electrode.

12. A method of measuring a direct-current resistance of a plurality of ion selective electrodes in an electrolyte concentration measuring apparatus provided with the plurality of ion selective electrodes and one reference electrode, the method comprising:

measuring an electromotive force between at least one of the plurality of ion selective electrodes and the reference electrode;

measuring a voltage and a current between the at least one of the plurality of ion selective electrodes and the reference electrode; and

determining the direct-current resistance from the electromotive force, the voltage, and the current.

13. A method of measuring a direct-current resistance of a plurality of ion selective electrodes in an electrolyte concentration measuring apparatus provided with the plurality of ion selective electrodes and one reference electrode, the method comprising:

measuring an electromotive force between at least one of the plurality of ion selective electrodes and the reference electrode;

measuring a voltage and a current between two of the plurality of ion selective electrodes; and

determining a sum of resistance values of the two ion selective electrodes from the electromotive force, the voltage, and the current as the direct-current resistance.