Examinando por Autor "Mejuto, E."

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Characterization of absolute cavity radiometers for traceability to SI of solar irradiance
(IOP Science Publishing, 2022-08-12) Balenzategui, José; De Lucas Veguillas, Javier; Cuenca Alba, José; González Leiton, Ana María; Molero García, María; Fabero, Fernando; Silva, J. P.; Mejuto, E.; Muñoz, R.; Arce, A.; Instituto Nacional de Técnica Aeroespacial (INTA)
Solar-type cavity radiometers are instruments of the highest metrological level for measuring solar direct normal irradiance. To ensure their traceability and performance, they are periodically compared to the World Group of Standards, which realizes the World Radiometric Reference (WRR), in the International Pyrheliometer Comparisons (IPCs). Additionally, they can be characterized in an absolute way, with direct traceability to SI units and with their measurement uncertainty calculated. This paper describes the different techniques and procedures applied for the characterization and calibration of solar cavity radiometers, with the main results obtained to date in the case of an Automatic Hickey–Frieden (AHF) radiometer. Voltmeters, resistors, temperature sensors and the area of the precision apertures have been calibrated, while the effective absorptance, temperature coefficients, optical scattering and non-equivalence factor have been evaluated. The temperature dependence of the electrical current in the cavity heater has also been analysed. The resulting corrections obtained for the AHF by characterization are compatible with the WRR factors obtained by this instrument in the past IPCs. An uncertainty of 0.42% (k = 1) has been obtained, and this paper discusses further improvements that may be able to reduce this figure to the desired expanded uncertainty of U = 0.1% (k = 2).
Acceso Abierto
On the characterization of an AHF cavity radiometer and its traceability to WRR/SI
(CIEMAT, 2022-02-10) Balenzategui Manzanares, J. L.; De Lucas Veguillas, Javier; Cuenca, J.; Molero, M.; Romero, M. C.; Fabrero, F.; Silva, J. P.; Mejuto, E.; Ibañez, F.J.; Ministerio de Industria, Economía y Competitividad
In a complementary way to the comparison to WSG to get traceability to WRR (and consequently, to SI), a solar-type cavity radiometer can also be characterized, determining the deviations of the instrument from the ideal realization of the principle of electrical substitution and obtaining its total measurement uncertainty. This work summarizes different techniques and procedures applied for the characterization of an Eppley AHF radiometer. The approach for characterization is based on the analysis of the measurement model function of the instrument. Some results obtained from calibration and testing (voltmeter, area of the precision aperture, resistance of the leads, non equivalence factor), and from numerical simulation (effective absorptance, scattering) are presented. According to these results, current value of standard uncertainty for this instrument is about 0.28% but it is expected that further improvements in the equipment and tests can reduce this figure below 0.1% (1000 ppm) in the near future.