The conversion of single-beam monochromators to double-beam microspectrometers is described. The principal advantage of the present system over others used is a great improvement in the long-term stability of the electronics; other advantages include simplicity, compactness, and complete freedom from beats due to mains frequency pickup. The system has been designed for use, in conjunction with a polarizer, for the examination of fibers, small crystals, and small areas of oriented biological macromolecules as well as for microsamples.