A stepping-motor controlled sine drive positions the grating, which is mounted on a precision rotary table. The sine drive delivers a linear relationship between stepper motor motion and wavelength of interest. It includes a mechanism to change the wavelength selected by the software and to record the resulting changes in the measured quantity as a function of the wavelength. Scanning is possible for a desired wavelength range. This feature can save time whenever full wavelength range scan is not necessary.
The motorized turret is powered by a stepper motor mechanically coupled through a direct worm gear drive. Electronics is packaged inside the housing and has an RS-232 interface to the computer. For USB interface a Serial to USB converter is connected to the RS-232 output and a USB converter driver needs to be loaded on the computer so that it will recognize the USB interface as a virtual RS-232 serial port. There is also a fast and interactive graphical software interface allowing full control of all the spectrograph functions.