| 摘要 |
PURPOSE:To expand the measurig range when the adsorbing amount of the gas to be detected becomes a specified value or more, by moving the central wavelength of the light irradiated from a variable wavelength laser to the part where the absorption coefficient on a light absorbing characteristic curve of the gas to be detected is small. CONSTITUTION:In the circuit of the gas concentration detecting circuit, a moving point (c) of a switching circuit SW is contacted with a contact point (a) when each point on the gas absorption characteristic curve is located at the part higher than the chain line (i). Conversely, when each point on the curve is located at the part lower than the alternate long and short dash line (i), the moving point (c) is contacted with (b). When the moving point (c) is contacted with (b), a current is supplied to a driving power source 30 in order to irradiate the light from the laser 5. In this way, the operating point is moved to the part where the absorption coefficient in the light absorbing characteristic curve of the gas to be measured is small. As a result the range of the gas concentration to be measured is expanded. |
