| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a gas sensor of high precision by improving the S/N ratio of a circuit. <P>SOLUTION: This gas sensor has a first heating element 1 coming into contact with a gas to be detected, a reference resistor 2 connected in parallel to the heating element 1, the first switch 3 connected to the heating element 1 and the reference resistor 2, a power supply device 4 for supplying a current to the heating element 1 or the reference resistor 2 through the first switch 3, a voltmeter 5 for measuring both terminal voltages of the heating element or the reference resistor 2 and an arithmetic part 6 to which the first switch 3, the power supply device 4 and the voltmeter 5 are connected. The arithmetic part 6 changes over the first switch 3 to the reference resistor 2 to determine the control condition of the power supply device 4 for allowing at least three stages of currents to flow to the heating element 1 from both terminal voltages of the reference resistor 2 and changes over the first switch 3 to the heating element 1 in predetermined timing to successively allow a current to continuously flow to the heating element 1 for an established time under the control condition. Both terminal voltages of the heating element 1 after the elapse of the established time with respect to respective current values are taken in the arithmetic part 6 through the voltmeter 5 and a current is cut off to perform operation for operating the concentration of the gas to be detected to output the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
