Uncertainty analysis of photometer quality factor f_1'

Poikonen, Tuomas; Kärhä, Petri; Manninen, Pasi; Manoocheri, Farshid; Ikonen, Erkki

doi:10.1088/0026-1394/46/1/009

Cited by 9 publications

(15 citation statements)

References 2 publications

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“…Linear transformation of the response of RGB channels (color space conversion) into the photometric quantity can contribute to substantial errors without optical correction, ignoring the spectral discrepancy, since the photopic luminosity function V(λ) normally does not lie in the vector space spanned by R(λ), G(λ) and B(λ), λ being the wavelength of incoming radiation. The error tends to be unacceptable particularly when relatively narrow bandwidth light sources are involved [55] in illumination, including light-emitting diode (LED). To address this limitation, the spectral response of the image sensor has been rectified by optical filters.…”

Section: Spectral Responsementioning

confidence: 99%

Design and validation of a compact embedded photometric device for real-time daylighting computing in office buildings

Kämpf

Scartezzini

2019

Building and Environment

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Studies have shown that the exposure to daylight can have substantial visual/non-visual benefits for building occupants. To optimise daylighting provision while maintaining a comfortable visual environment, daylighting control systems have been investigated by architectural design and academic research for a number of years. However, real-time regulation of daylighting in buildings requires transient daylighting simulation with high accuracy and, daylighting simulation, as performed to date, is significantly impacted by the employed sky luminance distribution models which only crudely reproduce the real sky characteristics due to oversimplification and limited luminance sampling inputs. In this paper, an embedded photometric device is proposed to combine high dynamic range (HDR) imaging based highresolution sky luminance monitoring with quasi real-time on-board daylighting computing, composed of a low-cost image sensor and a field programmable gate array (FPGA) microprocessor. A deliberate calibration procedure of the whole imaging system, regarding its spectral response (spectral correction error f'1 = 8.89%), vignetting effect and signal response, was formulated and validated experimentally. The device was made to measure a wide luminance range (150 dB) including that of the direct solar disk, sky vault, and landscape simultaneously. Finally, experiments during predominant clear and overcast sky conditions were conducted respectively to assess its performance in daylighting simulation, both qualitatively and quantitatively. The experimental results demonstrated its quality in solar tracking as well as its capability to reduce daylighting simulation error to 1 7 ∼ 1 3 of that of a common practice using the conventional Perez all-weather sky model for workplane illuminance calculation in office buildings.

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Section: Spectral Responsementioning

confidence: 99%

Design and validation of a compact embedded photometric device for real-time daylighting computing in office buildings

Kämpf

Scartezzini

2019

Building and Environment

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“…The wavelength steps in the spectral data affect the magnitude of the uncertainties in TOC created by spectrally random components. In our full-spectrum TOC retrieval, the number of data points n, which is smaller with a larger wavelength step interval, affects uncertainties with a factor of 1/ √ n, as demonstrated in Kärhä et al (2017b); Poikonen et al (2009).…”

Section: Atmoz Field Measurement Campaign and Instrument Descriptionmentioning

confidence: 99%

Uncertainty analysis of total ozone derived from direct solar irradiance spectra in the presence of unknown spectral deviations

et al. 2018

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Abstract. We demonstrate the use of a Monte Carlo model to estimate the uncertainties in total ozone column (TOC) derived from ground-based direct solar spectral irradiance measurements. The model estimates the effects of possible systematic spectral deviations in the solar irradiance spectra on the uncertainties in retrieved TOC. The model is tested with spectral data measured with three different spectroradiometers at an intercomparison campaign of the research project “Traceability for atmospheric total column ozone” at Izaña, Tenerife on 17 September 2016. The TOC values derived at local noon have expanded uncertainties of 1.3 % (3.6 DU) for a high-end scanning spectroradiometer, 1.5 % (4.4 DU) for a high-end array spectroradiometer, and 4.7 % (13.3 DU) for a roughly adopted instrument based on commercially available components and an array spectroradiometer when correlations are taken into account. When neglecting the effects of systematic spectral deviations, the uncertainties reduce by a factor of 3. The TOC results of all devices have good agreement with each other, within the uncertainties, and with the reference values of the order of 282 DU during the analysed day, measured with Brewer spectrophotometer #183.

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“…(13) The points P locate uniformly on the surface of an N + 1dimensional unit sphere and fulfill equation (11).…”

Section: Mathematical Description Of the Error Functionmentioning

confidence: 99%

Method for estimating effects of unknown correlations in spectral irradiance data on uncertainties of spectrally integrated colorimetric quantities

Kärhä¹,

Vaskuri²,

Mäntynen³

et al. 2017

Metrologia

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Spectral irradiance data are often used to calculate colorimetric properties, such as color coordinates and color temperatures of light sources by integration. The spectral data may contain unknown correlations that should be accounted for in the uncertainty estimation. We propose a new method for estimating uncertainties in such cases. The method goes through all possible scenarios of deviations using Monte Carlo analysis. Varying spectral error functions are produced by combining spectral base functions, and the distorted spectra are used to calculate the colorimetric quantities. Standard deviations of the colorimetric quantities at different scenarios give uncertainties assuming no correlations, uncertainties assuming full correlation, and uncertainties for an unfavorable case of unknown correlations, which turn out to be a significant source of uncertainty. With 1% standard uncertainty in spectral irradiance, the expanded uncertainty of the correlated color temperature of a source corresponding to the CIE Standard Illuminant A may reach as high as 37.2 K in unfavorable conditions, when calculations assuming full correlation give zero uncertainty, and calculations assuming no correlations yield the expanded uncertainties of 5.6 K and 12.1 K, with wavelength steps of 1 nm and 5 nm used in spectral integrations, respectively. We also show that there is an absolute limit of 60.2 K in the error of the correlated color temperature for Standard Illuminant A when assuming 1% standard uncertainty in the spectral irradiance. A comparison of our uncorrelated uncertainties with those obtained using analytical methods by other research groups shows good agreement. We reestimated the uncertainties for the colorimetric properties of our 1 kW photometric standard lamps using the new method. The revised uncertainty of color temperature is a factor of 2.5 higher than the uncertainty assuming no correlations.

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Uncertainty analysis of photometer quality factor f_1'

Cited by 9 publications

References 2 publications

Design and validation of a compact embedded photometric device for real-time daylighting computing in office buildings

Design and validation of a compact embedded photometric device for real-time daylighting computing in office buildings

Uncertainty analysis of total ozone derived from direct solar irradiance spectra in the presence of unknown spectral deviations

Method for estimating effects of unknown correlations in spectral irradiance data on uncertainties of spectrally integrated colorimetric quantities

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