An apparatus and method for utilizing NIR spectrography for measuring major constituents of substances in real time includes a monochromator or other sensor having no moving optical parts. At least one of the monochromator and the substance are moving relative to one another. An NIR radiation source irradiates a substance and the reflected or passed-through radiation is transmitted to the monochromator, which isolates and detects narrow portions of the received spectrum. By analyzing the intensities and wavelengths of the received radiation, the presence and amount of major constituents of the substance can be determined.