| 摘要 |
PURPOSE:To measure small potential changes simply and accurately, by operating a semiconductor ion sensor at constant current, and measuring the potential of the comparison electrode it that time. CONSTITUTION:An ion sensor 11 is dipped in an electrolyte 13, and a constant voltage VD is supplied to input terminal 14 of a drain electrode D, and a source electtode S is grounded through a reference resistance 15. A potential control circuit 17 to control the potential at point B of a comparison electrode 16 so that the potential at point A of the electrode S be constant is connected between the two electrodes. Operating the sensor 11 at the constant current, when the potential VGS of the electrode 16 in the electrolyte 13 is measured, the changes in ion concentrations pH x1 to x2 become as shown in the diagram, where the corresponding potential difference DELTAVGS is equal to the change in surface potential DELTAphix12. Setting the drain current IDS at constant current, and compensation may be effected at voltage VGS. Hence, operating the semiconductor sensor 11 at the constant current, the ion potential of the change in a small surface potential of the electrode 16 may be measured at high precision. |
