SI Traceability of Calibration for Distance Measurement - Vaisala Lidar Ceilometer CL61

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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