Patent ID: 7597789

Claim:
An oxidation-reduction potentiometer comprising: a working electrode, a reference electrode, an impedance reducing circuit, and oxidation-reduction potential measuring means, wherein the working electrode generates a potential indicating the degree of oxidation-reduction reaction when immersed in a liquid, the reference electrode generates a reference potential when immersed in the liquid, the impedance reducing circuit reduces an impedance which occurs between the working electrode and the reference electrode when the electrodes are immersed in the liquid, the oxidation-reduction potential measuring means measures an oxidation-reduction potential based on an interelectrode voltage which is a difference between the potential generated from the working electrode indicating the degree of oxidation-reduction reaction and the reference potential generated from the reference electrode in reducing the impedance by the impedance reducing circuit, and the oxidation-reduction potential measuring means comprises: reducing circuit switching means, interelectrode voltage measuring means, a comparison coefficient computing section, a comparison coefficient storing section, and an oxidation-reduction potential computing section, wherein the reducing circuit switching means switches the impedance reducing circuit to an unconnected state and to a connected state between the working electrode and the reference electrode, the interelectrode voltage measuring means measures an interelectrode voltage, which is a difference between a potential generated from the working electrode indicating the degree of oxidation-reduction reaction and a reference potential generated from the reference electrode, when the impedance reducing circuit has been switched to the unconnected state and when the impedance reducing circuit has been switched to the connected state by the reducing circuit switching means, the comparison coefficient computing section computes, in an adjustment mode, a comparison coefficient by dividing the interelectrode voltage in the unconnected state by the interelectrode voltage in the connected state, wherein said interelectrode voltages are measured when the electrodes are immersed in a reference liquid, the comparison coefficient storing section stores the comparison coefficient computed by the comparison coefficient computing section, and the oxidation-reduction potential computing section computes, in a normal mode, an oxidation-reduction potential as the interelectrode voltage in the unconnected state by multiplying the interelectrode voltage in the connected state, measured by the interelectrode voltage measuring means when the impedance reducing circuit has been switched to the connected state and the electrodes are immersed in a test liquid, by the comparison coefficient stored in the comparison coefficient storing section.