| 摘要 |
PURPOSE:To improve the resolution of a ventilation level requested when a gas sensor is utilized for a ventilator, etc., without increasing the overall sensitivity, and to eliminate malfunction due to too high sensitivity by utilizing the oscillation characteristic of a multivibration circuit. CONSTITUTION:The gas sensor 30 decreases in electric resistance value when gas is brought into contact with it, the partial voltage of a resistance 28 rises, and the potential at a point U varies. The multivibrator circuit consists of resistances 40, 43, 44, and 46, capacitors 42 and 45, and NPN transistors (TR) 41 and 47, and the inversion time of the time constant circuit consisting of the resistance 43 and capacitor 42 is influenced by the potential at the point U to vary the width of an oscillation pulse. The variation in pulse width in a warning area and a drift area due to the variation of environment is less than the variation width of the resistance value of the sensor and large at the ventilation level, improving the resolution. |
