A system permitting the automatic recording of ultraviolet and visible reflection spectra has been constructed, In which a function generating potentiometer, operating in synchronism with the wavelength drive of a conventional spectral reflectance apparatus, attenuates the phototube output to compensate for the spectral distribution of the light source, the wavelength dependence of the monochromator transmission, and the spectral sensitivity of the phototube. The potentiometer is tapped at points corresponding to about 100A intervals from 2200A to 7000A, and the resistances between taps are adjusted to give a constant recorder deflection when MgO is used as a sample. Once the potentiometer has been adjusted in this way, a direct record of spectral reflectance of an “unknown” sample is obtainable in a few minutes.
JAMES H. SCHULMAN and CLIFFORD C. KLICK, "An Apparatus for Automatic Recording of Reflection Spectra," J. Opt. Soc. Am. 43, 516-516 (1953)