User manual VAISALA TDL BROCHURE

[. . . ] / TECHNOLOGY DESCRIPTION JUNE 2009 Vaisala SPECTRACAP® and TDL Technology benefits The Vaisala SPECTRACAP® Sensor challenges the conventional oxygen measurement technologies by a laser based oxygen measurement. [. . . ] Note how the oxygen absorption does not overlap with other atmospheric gases. 1. 0E-22 1. 0E-23 1. 0E-24 0. 7 0. 8 0. 9 1. 0 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 wavelength (µm) Optimum optical and mechanical design The Vaisala SPECTRACAP® Sensor introduces a novel optical path arrangement where the laser light source, optical components, and the light detector are mounted within the same rigid structure. See Figure 2 below. Long-term stability The extreme stability of the Vaisala SPECTRACAP® Sensor is based on the combination of the optical absorption principle and the highly optimized sensing algorithms, including a built-in reference measurement. The employed semiconductor lasers show a lifetime of more than 10 years in continuous operation. Such a long lifetime enables considerable savings during the product life cycle as maintenance is seldom needed. These compensations aid in achieving the most accurate measurement in varying environmental conditions. The automatic temperature compensation is based on integrated temperature sensor, whereas the pressure, temperature, and carbon dioxide compensations require parameter values set by users. Figure 2: The passage of light int he SPECTRACAP® sensor probe used in the OMT300 series transmitters. Compensation of environmental parameters Since the oxygen measurement in the SPECTRACAP® Sensor is to some extent affected by environmental conditions, there are built-in compensations for temperature and and pressure as well as for water and carbon dioxide content of the background gas. 23 Interferences and optical feedback to the laser have been eliminated by optimal design of tilt angles, reflected light analysis, stray light control, and apertures. The SPECTRACAP® Sensor has a design where the laser light source and the detector are placed behind a protective window. The wetted parts are made of stainless steel and optical glass, which ensures good tolerance against aggressive chemicals in a variety of process environments. The SPECTRACAP® Sensor is ideal for direct insertion into the measurement location. 22 O2 [%O2] 21 20 19 Oct-2005 Dec-2005 Feb-2006 Mar-2006 May-2006 Jul-2006 Aug-2006 Oct-2006 Nov-2006 Jan-2007 Mar-2007 Figure 3: A 16-month outdoor test data for an OMT300 series 02 transmitter. [. . . ] All specifications -- technical included -- are subject to change without notice. [. . . ]