| 摘要 |
PURPOSE:To stabilize that temperature of a porcelain resistor body and to improve measuring accuracy by detecting the temperature of the porcelain resistor body of a semiconductor gas detecting element by using temperature characteristics of a heating body, and controlling the pulse width of a pulse voltage to be applied to the heating body. CONSTITUTION:The porcelain resistor body comprises MgCrO4-TiO2. On both sides of the resistor body, glazed resistor bodies including Pt are formed by the screen printing method as an electrode 2 and an electrode 3 which also serves as a heating body. The temperature is detected by measuring the resistance of the electrodes. Meanwhile, resistors (a bridge circuit) are constituted by combining them with the heating body (resistance between a terminal 9 and a terminal 11) of the detecting element S. The pulse width of the output of a pulse width modulator PWM is controlled so that the unbalanced potential of said bridge circuit becomes small. In this device, the temperature of the porcelain resistor body (gas detecting part) of the detecting element is kept constant, and the measuring accuracy is improved. |
