Browsing by Author "August, Leevi"

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    Aaltovoimaloiden sähköisten voimalinjojen konseptit
    (2020-05-25) August, Leevi; Routimo, Mikko; Sähkötekniikan korkeakoulu; Turunen, Markus
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    Development of a Reference Spectrometer with a Supercontinuum Laser Source
    (2024-06-17) August, Leevi; Manoocheri, Farshid; Sähkötekniikan korkeakoulu; Ikonen, Erkki
    In this work, a new reference spectrometer is developed and tested to maintain and expand the measurement capabilities at the Metrology Research Institute of Aalto University. The new spectrometer is a single beam instrument for measuring regular spectral transmittance in the wavelength range of 200 nm to 2100 nm. To automate the facility a LabVIEW based system is programmed. An optical fiber-based supercontinuum laser was chosen as the primary light source due to its brightness and broad bandwidth. The measurement setup was further expanded into the UV-range by implementing a laser driven xenon lamp. Light from these sources was made monochromatic using a diffraction grating monochromator and order sorting filters. To provide detection in the broad wavelength range an averaging sphere with a photomultiplier tube, silicon- and indium gallium arsenide photodiodes are used. Characterization of the spectrometer and its components is performed together with spectral transmittance measurements of bandpass and neutral density filters. These measurement results are compared with previous results of existing devices to evaluate the accuracy and precision of the facility. Uncertainties related to wavelength calibration, detector linearity, light source stability, stray light and interreflections are determined for the transmittance measurements performed. As examples, the absolute standard uncertainty for a neutral density filter measurements are estimated at 5.3⋅10-5 for ND10A and 1.1⋅10-5 for ND20A. For measured bandpass filters a peak absolute uncertainty for the slopes is estimated at 10-2.