| 摘要 |
PURPOSE:To expedite the substitution of gas, to improve the responsiveness of measurement and to enable the protection of a measuring electrode from thermal impact, by providing a gas channel from inflow to outflow of a gas to be measured which passes in the vicinity of the base end part of an oxygen sensor formed of a solid electrolyte. CONSTITUTION:A plurality of oxygen sensors 10 fitted to a main pipe 1 are set in the flow of a gas to be measured. The gas enters an internal space 21 through a filter 15 from gas inflow ports 24 provided in four spots of a filter cover 2 of a sensor 10, and the substitution of the gas is implemented by gas diffusion and thermal convection due to a difference in concentration of the gas, in a place from the internal space to a measuring electrode. The other part of the gas passes through a gas inlet-outlet port 25, a gas passage and a gas exhaust port 22 and is released outside. When a calibration gas is introduced through an introduction pipe 18, it is passed through an introduction port 20 and the inlet-outlet port 25 and filled up in the space 21. Since the space 21 is put in a state of positive pressure on the occasion, the inflow of the gas to be measured is prevented. Part of the calibration gas is brought into contact with the measuring electrode by pressure introduction. The other part of the calibration gas is exhausted from the exhaust port 22 through the gas passage at the time point where the space 21 is put in a state of negative pressure. |
