An Interface Circuit for Ion-selective Electrode Sensors

Abstract

This design uses the ion-selective electrode method to measure the pH, or the ion concentration of a certain solution. The small DC electrical potential signal which is generated by ion selective electrode and reference electrode is put into an amplifier of high input impedance and linear. The MSP430F1611 MCU which is taken as the master control system converts the amplified signal by the 16-bit AD converter. Then the LCD screen shows the electrical potential difference between the two electrodes. A PC display program is written through the LabVIEW to get the curve of the electrical potential difference between the two electrodes at different sampling time. To analyze and process the electrical potential difference between the electrode systems of different solution, and then the pH, or a certain ion concentration of the solution is get. Besides, before the electrical potential signal passing the amplifier, the design adds a dual 8-channel analog switch which can enable the switch between the 8 groups of electrodes and ensure the simultaneous measurement of multiple electrodes.