Establishment of Illuminance Scale at UME with an Accurately Calibrated Radiometer

Construction of Two-Axis Goniophotometer for Measurement of Spatial Distribution of a Light Source and Calculation of Luminous Flux

“…The spectral responsivity, uniformity and linearity of the photometer head as well as the spectral transmittance of the V (λ)-filter were characterized by the TUBITAK UME detector calibration and characterization facilities [18][19][20]. The diameter of the monochromatic beam was aligned to ≈ 2 mm and a substitution method with the reference trap detector was used to obtain the relative spectral responsivity variation of the photometer head.…”

“…The photometer head linearity was checked at wavelengths of 543.2 nm and 632.8 nm over an output photocurrent range of 2×10 −3 to 2×10 −10 A [20], which corresponds to be used for illuminance measurements within 8.4 × 10 −3 to 8.4 × 10 3 lx. For typical working photocurrents of 30 nA to 30 µA, the nonlinearity was observed to be ±0.02%.…”

“…For typical working photocurrents of 30 nA to 30 µA, the nonlinearity was observed to be ±0.02%. The uniformity of the photometer head was measured by using a computer-controlled optical setup, where the acceptance area of the photometer head was scanned over the central area of 10 mm × 10 mm at wavelength of 632.8 nm [20]. The responsivity of the photometer head was recorded for each scanning interval of 10 µm in entrance aperture of the photometer head.…”

“…The illuminance responsivity of the photometer head has been calibrated at TUBITAK UME using the new detector-based illuminance scale with an expanded uncertainty of 0.30% (k = 2) [20]. The photometer head is recalibrated annually by comparing it with the absolutely calibrated filter-radiometers constructed for the realization of the candela.…”

Estimation of Calibration Uncertainties in the Detector-Based Photometric Calibrations

“…A detector is said to be linear if its output signal is directly proportional to the incident power. The linearity of the RP had been measured using a flux--addition technique [11]. Measurements had been performed between the photocurrents of 2 nA and 2 mA by applying different neutral density filter combinations to the beam ways.…”