earticle

영어

With the maturity of precision manufacturing and fast signal processing technology, FTIR may now be used in an actual open air field. This paper summarized the present technology trend involving remote chemical detection and explained the detection principle of remote chemicals by using the twolayer model of the atmosphere. Since the FTIR for the remote chemicals is based on the measured temperature difference between background and gas, the minimum detection level of temperature difference is the key parameter for evaluating system performance.. The merits of system performance are simulated theoretically from the photoconductive detector noise model. NEDT (Noise Equivalent Differential Temperature), which is dependent on spectral resolution and signal integration time, was used to analyze in order to get the best signal-to-noise ratio. For practical operations, it was determined that a proper trade-off between lowering the NEDT and number of averaging data is necessary. Intermittent correction of output signal is needed from the unavoidable external perturbation of temperature and mechanical vibration. In order to estimate the system's calibration period, the approximated formula of the responsivity variation was derived as a function of the environmental temperature variation from the assumed linear dependence between spectral radiance and instrument output signal.