| 摘要 |
1,242,808. Infrared gas analyzer. BECKMAN INSTRUMENTS Inc. Sept. 9, 1969 [Sept. 18, 1968], No.44398/69. Heading G1A. In a non-dispersive infrared gas analyzer having a flow cell 11 for the sample gas, an infrared source 10 and a detector 13, such as a thermistor bolometer, there is provided a rotatable calibration blade 18 having a known ratio of transmissive area to blade area, the calibration of the instrument being effected by first flowing air through the cell with the blade stationary and in a transmissive position and adjusting potentiometer 35 to give a zero reading on a meter 37, and secondly rotating the blade, with air still flowing in the cell, and adjusting potentiometer 39 to give a second reading on the meter. With these two known calibration points, if the cell length is known the meter 37 may be calibrated to read directly in concentration of a constituent of a gas being investigated and flowing through the cell, and a recorder may be provided instead of a meter. The blade 18 is rotated at a frequency greater than the detector responsive time, and a conventional chopper 16 is provided to modulate the detector output, which is amplified (31) then rectified (32) before being fed to a D. C. amplifier 34 and subsequently to the meter 37. To investigate absorption at a given wavelength, an infrared filter 28 is provided. |
