ION CONCENTRATION MEASURING APPARATUS

摘要

PURPOSE:To enable handy monitoring of the condition of an ISFET, by providing a detection circuit between a gate electrode and a reference electrode to measure complex impedance between the gate electrode and a liquid to be inspected. CONSTITUTION:A gate electrode 24 of an ISFET20 is connected to an AC current source 27 and an amplitude phase measuring device 28 together with a reference electrode 23, where the phase of the amplitude phase measuring device28 is based on the phase of the AC power source 27. A complex impedance value R-jX between the gate electrode 24 of the ISFET20 and a liquid 22 to be inspected from the amplitude of a AC current applied from the AC current source 27 and the amplitude and the phase of the AC voltage measured with the amplitude phase measuring device 28 is calculated with a vector divider 29 and displayed. When the insulation state of a gate insulation film of the ISFET20 and the water content state of a gate ion sensitive film are to learned, the resistance component R of the complex impedance is read while the capacity component X thereof is read when the amount of components adsorbed on gate sensitive film is to be learned. Thus, the monitoring of the state of the ISFET can be done in a handy manner.