DETECTION OF OIL CONTAMINATION IN SEA WATER. VOLUME 3: ENGINEERING EVALUATION AND IMPROVEMENT OF THE INFRARED OLEOMETER

An instrument for monitoring oil contamination in sea water is described. Specificity for hydrocarbons is achieved by differential observations of infrared absorption at three wavelenghts: 1.193, 1.211, and 1.229 microns. Absorption at 1.211 microns is due to methylene groups present in hydrocarbons. Absorption levels at this wavelength are compared with absorption values at 1.193 and 1.229 microns. The comparison is made by a special chopper that acts as a modulator to deliver a balanced output to two detectors for common mode rejection of several sources of error and an unbalanced output in the presence of oil. (Author)