| 摘要 |
PURPOSE:To automatically correct zero point fluctuation caused by the fluctuation of the electrostatic capacity of a cable as well as of the insulation resistance by impressing the fixed voltage intermittently on the opposing electrodes to perform subtruction between the conductivity signals and the zero point error signals. CONSTITUTION:The fixed voltage V is impressed intermittently on the electrodes X and Y from inside of the current/voltage transducer 1 through the intermittent working of the switch SW. When the switch SW is in the OFF state, the zero point error voltage caused by the insulation resistance Rb and Rc, the electrostatic capacity Cb of the cable CBL is retained by the capacitor C1 through the gate Q. Thereafter, when the switch SW is turned ON, the voltage based on the conductivity of the substance to be measured is supplied to the operation circuit 3 to retain the difference voltage from the zero point error voltage through the gate Q2. Thereby the correct conductivity measurement value can be obtained and also the cable length as well as the frequency of the impressed AC signals can be freely selected. |
