A typical FT-IR spectrometer will scan down to the long wavelength limit of approximately 400 cm-1 limited by the optical components such as the beamsplitter and detector which contain potassium bromide (KBr). However, there are a growing number of applications where the materials of interest exhibit spectral absorptions much further into the far-infrared region requiring instruments that can scan down below 100 cm-1. This application note describes how the Spectrum 3 tri-range version allows for multiple optical components to be installed on a single instrument allowing for coverage of a wide spectral range from 10,000 - 30 cm-1.