| 摘要 |
<p>A highly precise gas sensor having an improvement of circuit S/N ratio. An end (1a) of a heater element (1), which contacts with a gas to be detected, is connected to an end (2a) of a reference resistor (2), while the other ends (1b,2b) of the heater element (1) and reference resistor (2) are connected to respective contacts of a first switch (3). This first switch (3) is connected to a power supply apparatus (4) for supplying a current to the heater element (1) or the reference resistor (2). A voltage measuring part (5), which measures the voltage occurring across the heater element (1) or reference resistor (2), is connected in parallel to the heater element (1) or reference resistor (2) during switching of the first switch (3). An arithmetic part (6) switches the first switch (3) to the reference resistor (2) side and decides, based on the voltage occurring across the reference resistor (2), a control condition of the power supply apparatus (4) for supplying, to the heater element (1), a stepwise current having a shape of at least three steps, and further switches the first switch (3) to the heater element (1) side at a predetermined timing. The stepwise current having the shape of at least three steps is sequentially supplied to the heater element (1) in a continuous manner, and the voltages across the heater element (1) corresponding to the respective current magnitudes are measured by a voltage measuring part (5) and then applied to the arithmetic part (6). Then, the current supply is stopped, and the concentration of the gas to be detected is calculated for output.</p> |
