To solve problems that a correct sensor output is hard to obtain by measurement using a conventional non-dilution method, because a liquid contacting a sensor is replaced by a sample solution or by a calibration liquid and the difference in pH, Cl-ion concentration, temperature, etc., between the respective solutions produce a difference in sensor sensitivity between calibration and measurement, and it takes much time to obtain a result and a large amount of cleaning liquid is used, because a process has so far been inserted between measurement and calibration for cleaning the sensor and a liquid sending system.
A mixed liquid is prepared by mixing the sample and the calibration liquid at a prescribed ratio. By performing calibration after measurement or before the measurement, the solution contacting the sensor in measurement and that in calibration are made substantially equal. This holds down an error due to variations in pH, Cl-ion concentration, temperature, etc., of the sample to enhance measurement accuracy. The cleaning between the calibration and the measurement is omitted to make it possible to shorten measurement time and reduce the amount of cleaning liquid.
NAKAMURA KAZUHIRO
YAMAZAKI HIRONORI
HIRUTA YOSHIKI
NAGANO SHINJIRO
KATAYAMA HISAMI
