| 摘要 |
PURPOSE:To exactly detect an oxygen concn. without being affected by a change with time and temp. change by connecting an external resistor selected to meet the ambient temp. of a galvanic cell to said cell and determining the ratio between the 2nd and subsequent cell outputs and the first cell output as a prescribed output ratio. CONSTITUTION:A temp. sensor 6 is disposed around the galvanic cell 1 to measure 7 the temp. A fixed resistor 8 having optimum resistance is selected by an external resistor selecting circuit 10 to meet the measured temp. and is connected to the cell 1. The output voltage of the cell 1 is inputted to a central processing circuit 12 after amplification 4 and AD conversion 11. The ratio thetan=en/e0 between the 2nd and subsequent output voltages en and the 1st output voltage e0 is calculated in the circuit 12. The ratio thetak=V1/V0 between the output V1 of 18.0% oxygen concn. (dangerous concn.) in the atm. and the output V0 of 20.6% oxygen concn. is preliminarily determined. The ratios thetan and thetak are compared and the oxygen concn. is displayed 13 if thetan<=thetak. The oxygen concn. is thus exactly detected without being affected by the ambient temp. and change with time as the output ratio is decreased to the prescribed value or below by connecting the selected external resistor to the galvanic cell. |
