The patented multichannel optical design of the SpectraMax® Plus384 Absorbance Microplate Reader mimics a dual beam spectrophotometer, measuring each sample in the plate directly, eliminating measurement error due to variations in light output between optical fibers on other instruments for more reliable data reporting. The nine-channel system delivers both high precision and speed when reading cuvettes, 96-well, and 384-well microplates for endpoint measurements, kinetic assays, and spectral scans. The optical system of SpectraMax Plus384 Microplate Reader is built around a monochromator, which allows for selection of up to six wavelengths at a time for absorbance detection in the UV-visible wavelength range (190 nm - 1000 nm). Narrow bandwidths deliver increased measurement accuracy and linearity over the widest range of assays, including DNA quantitation in the UV range. Using the patented PathCheck® Pathlength Measurement Technology, the SpectraMax Plus384 Microplate Reader transforms each well in a microplate to a fixed optical path length cuvette. This temperature-independent normalization corrects for varying well volumes and can eliminate standard curves by allowing the calculation of concentrations directly from the absorbance with a known extinction coefficient, as exemplified with nucleic acid and protein quantification.