| 摘要 |
There is provided a highly accurate gas sensor by improving an S/N ratio of a circuit. One ends (1a), (2a), of heat generating element (1) and reference resistor (2) brought into contact with a detected gas are commonly connected, and respective contacts of first switch (3) are respectively connected to respective sides of other terminals (1b), (2b). First switch (3) is connected with power source apparatus (4) for supplying a current to heat generating element (1) or reference resistor (2). Voltage measuring portion (5) for measuring a voltage across both ends generated across both ends of heat generating element (1) or reference resistor (2) is connected in parallel with heat generating element (1) or reference resistor (2) when first switch (3) is switched. Operating portion (6) switches first switch (3) to a side of reference resistor (2) and switches first switch (3) to the side of heat generating element (1) by a predetermined timing by determining a condition of controlling power source apparatus (4) for supplying at least 3 stages of step-like currents to heat generating element (1) from the voltage across both ends generated at reference resistor (2). Heat generating element (1) is continuously supplied with successively at least 3 stages of step-like currents to carry out operation of inputting the voltage across both ends of heat generating element (1) in correspondence with magnitudes of the respective currents to operating portion (6) by way of voltage measuring portion (5) and calculating and outputting a concentration of a detected gas by making the current off.
|
