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The Importance of Factory Calibration
Factory calibration is an integral step in the manufacture and repair of all LI-COR measuring instruments. The characteristics of optical and other components change with time, and may be affected by environmental conditions. Data of a critical nature may require more frequent calibrations than those suggested, as well as calibrating under conditions of actual use (e.g., same temperature). Many instruments also require user calibration to compensate for daily, or more frequent, changes in barometric pressure and/or temperature. A more extensive factory recalibration is recommended for many LI-COR instruments; the recommended frequency, and what is included with the factory recalibration for each instrument can be found by selecting your instrument below.
Due to normal variation in internal optical components, it is necessary to characterize each sensor by measuring its output based on a standardized source. For LI-COR light sensors, calibration data is supplied as a ‘calibration constant’ that indicates the amount of sensor output for a given amount of measurable energy.
The factory calibration of LI-COR gas analyzers characterizes the relationship between the light absorptance and actual gas concentrations for each analyzer. This involves making a series of automated measurements with traceable reference gas concentrations. Measurements are done in controlled conditions at a range of temperatures to verify performance and (depending on the analyzer model) characterize any temperature correction parameters. For dual species analyzers, any cross-sensitivity correction parameters required for that particular model are generated during the factory calibration.
Following the factory calibration, the calibration data are analyzed, and calibration coefficients are generated and loaded into the analyzer. This is followed by an automated user calibration (analyzer zero and span), then a final, independent data set is collected to verify that the analyzer meets all accuracy and cross sensitivity specifications. Each analyzer is shipped with a copy of its calibration certificate. The calibration and final check data and analyses are available upon request.