TWO-DIMENSIONAL PH MEASURING DEVICE

摘要

PROBLEM TO BE SOLVED: To calibrate a device by a solution other than the standard solution of the JIS standards by correcting it by outputs of a field effect transistor ion sensor (ISFET) incorporated in the same side as a sensor surface. SOLUTION: A sensor surface 6 for pH measurement is formed in one side of a Si substrate 4 and an ISFET 15 is incorporated in the same side as it. A counter electrode 9 and a reference electrode 10 are dipped in a sample 8 stored in a cell 7 and a prescribed bias voltage is applied from a potentiostat 20 so as to generate a depletion layer. A probe beam 14 is intermittently irradiated from a laser beam source 3 so as to generate AC photoelectric current on the substrate 4. This photoelectric current reflects and measures the pH value of the sample 8 being in contact with the sensor 6 in a point matched with an irradiation point of the substrate 4. A device is calibrated by using as the reference pH value the signal output of the ISFET 15 which is separately calibrated by standard solution. This measurement pH value is not changed by impedance of the sample 8 so that the device can be calibrated by solution except for the standard solution of the JIS standards.