IN-LINE MONITOR

摘要

PROBLEM TO BE SOLVED: To calibrate the span of a change with the passage of time of an in-line monitor without making a fluid for calibration flow into a measuring cell by a method wherein the measuring cell is provided, a cell for calibration is provided, one out of both cells is changed over selectively, light is transmitted and the light which is passed through the cell is received. SOLUTION: A light source 4 and a photodetector 5 are fixed in such a way that their optical axes are aligned by a connecting arm, and an optical system set is formed. The light source 4 and the photodetector 5 are moved in parallel in such a way that they are aligned with the cell window 2a and the cell window 2b of a cell 2 or with the cell window 3a and the cell window 3b of a cell 3. Light from the light source 4 is incident on the photodetector 5 always at the same angle. Their optical axes are not drviated, and the detecting sensitivity of the light is not changed. A gas line L into which a gas S to be measured flows is connected to a semiconductor manufacturing apparatus 7. The apparatus 7 is connected to the downstream part of the meansuring cell 2. A liquid material 8 for the gas S to be measured is connected to its upstream part. When the gas S is made to flow into the apparatus 7, the gas S to be measured flows into the cell 2. When the component or the concentration of the gas S is measured or calibrated, the optical system set is slid to the side of the cell 3 for calibration. A known calibration gas C is made to flow into the cell 3. The sensitivity of the cell 3 is adjusted in such a way that a measured value becomes a known concentration.