MEASURING DEVICE OF TRANSMITTANCE FOR SMOKE

摘要

PURPOSE:To measure visual transmittance despite the change in the coefft. of wavelength by the constitution consisting of determining the visual transmittance from the relative value of the spectral transmittance signals of two wavelengths at the time of measuring the smoke density in a tunnel. CONSTITUTION:The light emitted from a projecting part passes the inside of smoke and arrives at the objective lens 1 in the photodetecting part, thence it is bisected by a half mirror 3 and the optical density of each wavelength is separated to two by a measuring circuit for spectral transmittace of wavelength lambda1 and a measuring circuit for spectral transmittance of wavelength lambda2. These are held in sample holding circuits 20-23. In a divider 33, the ratio of the ratio of the wavelengths lambda1, lambda2 to a logarithmic value, that is, the coefft. of wavelength is determined, by which the coefft. of correction for the transmittance is transmitted from a function generator 34 to a multiplier 36. In the multiplifer 36, the product of this coefft. of correction and the difference in the optical densities of the two wavelengths is calculated and the output thereof is converted to a visual transmittance by an index converter 37, so that the final output signal is obtained.