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SI Traceability of Calibration for Distance Measurement - Vaisala Lidar Ceilometer CL61
Accurate calibration is fundamental to the high measurement accuracy of Vaisala Lidar Ceilometer CL61. CL61 distance measurement is calibrated against a reference that is traceable to international standards (SI units). Calibration uncertainty is comprehensively analyzed and regularly verified by independent laboratory measurements. Accurate height measurements ensure the correct height coordinates for measured atmospheric variables.
1. SI traceability chain
The Vaisala Ceilometer CL61 units are individually calibrated at the Vaisala factory. Figure 1 illustrates the traceability chain of distance measurement calibration to International System of Units (SI). The working standard is a reference fiber optic delay-line. Traceability of the standard to SI units is established through an unbroken chain of documented time delay calibrations by National Metrology Institute (VTT-MIKES, Finland).
The calibration certificate provides details on the reference fiber optic delay-line. The working standard is calibrated regularly by VTT-MIKES. To guarantee consistent quality of calibration, process instrument changes are managed according to ISO 9001:2015 Quality Management System and the ISO 10012:2003 normative reference. The uncertainty of the calibration is determined according to JCGM 100:2008 (Evaluation of measurement data — Guide to the expression of uncertainty in measurement).
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