ASTM D6756 Standard Test Method for Determination of the Red Dye Concentration and Estimation of the ASTM Color of Diesel Fuel and Heating Oil Using a Portable Visible Spectrophotometer
7. Apparatus
7.1 Filter Spectrophotometer, is equipped with specimen chamber, visible wavelength source, four 10 nm +/- 2 nm (full width at half transmission maximum) bandpass wavelength discriminating filters having center wavelengths at 450 nm +/- 2 nm, 520 nm +/- 2 nm, 650 nm +/- 2 nm, and 700 nm +/- 2 nm. The bandpass filters are used in conjunction with the visible wavelength source to produce light in the blue, green, red, and far-red regions of the electromagnetic spectrum. A detector converts the transmitted light to an electronic signal that is processed by an A-D converter and a microprocessor.
7.2 Specimen Cell, constructed of polymethacrylate or clear optical glass having a path length of approximately 1 cm. If more than one cell is used for calibration, qualification, and sample measurement, the path length of the cells must be matched to +/- 0.001 cm.
