| 摘要 |
PURPOSE:To always display a correct measured value even in a long-time measurement, by a method wherein a specified voltage is applied between two electrodes at the start of the measurement and impurities are scattered with the potential down to zero between both the electrodes down after the end of the measurement. CONSTITUTION:Resistances R1 and R2 are set to ensure that a voltage outputted from a constant voltage circuit 1 gives a specified value. When a voltage to be measured is applied to a sensor section 3, current is outputted according to the mass of an object to be measured in a liquid to be measured. The current is converted with an I/V conversion amplifying section 4 into voltage and subjected to an A/D conversion 5 to be fed to an operational control section 6, which calculates the amount of substance to be measured from a digital value fed and the results are shown on a display section 7. In this case, the processing section 6 closes a switch SW to zero the potential at both poles of the sensor section 3, the condition which is held until a measurement start signal is outputted from the control section 6. This can scatter attached impurities or the like to eliminate drop in the measuring accuracy due to deterioration in the electrodes even when the measurement is restarted thereby assuring proper measuring accuracy. |
