| 摘要 |
PURPOSE:To measure the gas-transmitted light intensity without errors by a method which to obtain the difference output of the transmitted light and an offset amount based on a drift of a lock-in amplifier, the drift occurring between the time when a laser beam is transmitted and the time when it is interrupted. CONSTITUTION:An offset adjusting dial of a lock-in amplifier 7 is turned to make offset output 0. Then, the photometer is operated and, after the lapse of a predetermined time from starting of a laser to emit a laser beam, a shutter 3 is moved by a pulse motor 11 in a direction of an arrow (d) to interrupt the laser beam. This makes light input 0, so that an amplifier 7 outputs an offset voltage E0 only which corresponds to a drift having occurred during the predetermined lapsed time. This offset voltage is stroed in a memory 10 through an A/D converter 8. Then, the shutter 3 is returned in a direction of an arrow (e) causing the light from the laser 1 to transmit through a gas cell 4. When the transmitted light enters an infrared detector 5, a voltage E1 appears at an amplifier 7. By subtracting E0 from E1, it becomes possible to attain the true observed value without the offset amount. |
