Abstract: The concentration of a selected gas specie at a situs determined by directing a laser beam at the situs, the beam including a wavelength within the resonance absorption band of the gas specie, and measuring the intensity of the laser beam energy scattered from two spaced volumes along said beam at the situs. The ratio of measured intensities is a relative measure of the concentration of the gas specie at the situs.

Abstract: Sheet material in a rolling mill passes over a measuring roll on its way to a coiler and causes the production of length measuring pulses at the roll and coil wrap pulses at the coiler. Sometimes slipping occurs between the moving sheet and measuring roll, thus causing variable errors in length measurements. A digital computer first stores predetermined constants and all pulse data until the tail end of the sheet is detected, then performs a regression analysis on the pulse data to compensate for measurement errors, and subsequently integrates the corrected data to obtain a highly accurate coil sheet length calculation. The computer also corrects the coil sheet length calculation for additional errors caused by a partial last wrap on large diameter coils, as well as for any significant differences in sheet thickness from a nominal value.