Wavelength modulation and noise reduction using a minicomputer-controlled UV-VIS-NIR recording spectrophotometer

Sources of noise in quantitative absorption and emission spectrometric measurements which can decrease the precision and accuracy of the measured signals are investigated. White and nonwhite noise sources are discussed and compared graphically to the photon-limited noise. Noise sources in the encoding and decoding processes are considered. The minicomputer-controlled system is described, including the hardware and software used for signal measurement. The results obtained with the minicomputer-controlled system are presented. Wavelength modulation is discussed using the results of the noise study and the results found in the literature. The sensitivity of wavelength modulation is shown to result form selective modulation and effective averaging of a signal whose precision is limited only by photon statistics. The A/D converter is compared with photon counting on a praeseodymium peak. For equivalent integration times at low light levels, photon counting provides about ten times more noise reduction than the A/D converter.