Petri Kärhä | Aalto University (original) (raw)
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A constant-voltage method for accurate calibration of current-to-voltage converters has been stud... more A constant-voltage method for accurate calibration of current-to-voltage converters has been studied and implemented down to 1-pA level with expanded uncertainty (k=2) of 3800 ppm. The same method is implemented for the characterisation of standard resistors, which is crucial for the calibration itself. The goal of this work is to achieve accurate and traceable measurements for radiometric and photometric applications producing photocurrents at picoampere level.
A photometer used for on-line product testing of light-emitting diode (LED) buoy lanterns is cali... more A photometer used for on-line product testing of light-emitting diode (LED) buoy lanterns is calibrated for illuminance responsivity using two different methods. The first method is based on absolute calibration of the photometer with the CIE standard illuminant A light source, combined with spectral correction factors (SCFs) calculated from the measured spectral responsivity of the photometer and relative spectra of the LED lanterns. The second method is based on direct comparison with a characterized reference photometer using the LED lanterns as light sources. Comparison of the resulting correction factors shows that both methods agree within 1%. However, the second method includes geometrical aspects and LED characteristics that caused problems. These problems are discussed and the reasons for recommending the first method are given.
Polysulphone and spore-film UV-dosimeters compared to a UVI-monitoring instrument and two radiati... more Polysulphone and spore-film UV-dosimeters compared to a UVI-monitoring instrument and two radiation transfer model systems-Evaluations for a UV-dosimetry study 2004 of preschool children___________________________ 6 UVEMA: A new project exploring degrading effects of UV radiation on materials__________________________________ 9 Standard MEAN Ultraviolet Radiation for non-Extreme Exposure Conditions: definition and indoor reproduction _______ 11 Calibration of UV radiometers is needed to guarantee the relevance of measurements ______________________________ 14 Solar simulators as a tool for assessing the impact of UV radiation on organisms and ecosystems _____________________ 17 Long-term measurements of UV-solar radiation in Dortmund (Germany) ________________________________________ 20 Analysis of UV-B solar radiation in C.I.B.A. laboratory, Spain ________________________________________________ 22 UV-B and UVI measured and calculated in Valladolid, Spain. _________________________________________________ 25 Realising a primary spectral irradiance scale on deuterium lamps in the ultraviolet_________________________________ 29 Comparison of measurement devices for the measurement of erythemal solar ultraviolet radiation during an outdoor-worker study in Austria ______________________________________________________________________ 31 Realization of a new commercial radiometer for measurement of the total UV effective irradiance of sunbeds ___________ 33 Investigation of comparison methods for UVA irradiance responsivity calibration facilities__________________________ 35 The use of a single-monochromator diode array spectroradiometer for UV-radiation measurements ___________________ 37 GaAsP trap detector for UV measurement _________________________________________________________________ 39 Characterization of integrating spheres for ultraviolet radiometry ______________________________________________ 41 Surveillance of UV-sensors in UV-disinfection plants in water works ___________________________________________ 42 Calibration and characterization of UV sensors for water disinfection ___________________________________________ 44 Monitoring of low-and medium pressure mercury lamps in UV-disinfection plants for drinking water _________________ 46 Improved entrance optic for global irradiance measurements with a Brewer spectrophotometer_______________________ 48 Time resolved measurements of spectral radiant flux from VUV to NIR (160 nm < λ < ≈ 1000 nm) on Xe excimer lamps ____________________________________________________________________________________ 49 Improvements of a fast scanning double monochromator for UV-B monitoring ___________________________________ 51 Long-term experience in using deuterium lamp systems as secondary standards of UV spectral irradiance ______________ 52 Expanded Measurement Uncertainty of Spectral Measurements Outside of the Laboratory __________________________ 54 UV-Monitoring at Outdoor Workplaces-A Base for Well-Balanced Health Prevention Regulations___________________ 56 Extreme UltraViolet Phototherapy ______________________________________________________________________ 59 Photobiological quality control in UV phototherapy _________________________________________________________ 61 Personal UV-monitoring in health prevention and risk analysis ________________________________________________ 62
A method for determination of the effective measurement plane of measuring heads with diffusers i... more A method for determination of the effective measurement plane of measuring heads with diffusers is presented. The method was tested with three commercial photometers and four spectroradiometer diffusers. The shifts of the diffuser reference planes were determined to be 5 – 9 mm and 0 – 7 mm, respectively. This effect causes measurement errors up to 3 % if the detectors are calibrated and used at different distances from the light source.
Microbridges, also known as microglows or micro-filaments, are miniature silicon filaments that a... more Microbridges, also known as microglows or micro-filaments, are miniature silicon filaments that are used e.g. in analysers as light sources. A microbridge is brought up to incandescence by passing an electrical current through it. Temperature determination of an operating microbridge with a contact measurement is complicated due to the small size of the bridge and the heat loss via the contact probe.
A constant-voltage method for accurate calibration of current-to-voltage converters has been stud... more A constant-voltage method for accurate calibration of current-to-voltage converters has been studied and implemented down to 1-pA level with expanded uncertainty (k=2) of 3800 ppm. The same method is implemented for the characterisation of standard resistors, which is crucial for the calibration itself. The goal of this work is to achieve accurate and traceable measurements for radiometric and photometric applications producing photocurrents at picoampere level.
A photometer used for on-line product testing of light-emitting diode (LED) buoy lanterns is cali... more A photometer used for on-line product testing of light-emitting diode (LED) buoy lanterns is calibrated for illuminance responsivity using two different methods. The first method is based on absolute calibration of the photometer with the CIE standard illuminant A light source, combined with spectral correction factors (SCFs) calculated from the measured spectral responsivity of the photometer and relative spectra of the LED lanterns. The second method is based on direct comparison with a characterized reference photometer using the LED lanterns as light sources. Comparison of the resulting correction factors shows that both methods agree within 1%. However, the second method includes geometrical aspects and LED characteristics that caused problems. These problems are discussed and the reasons for recommending the first method are given.
Polysulphone and spore-film UV-dosimeters compared to a UVI-monitoring instrument and two radiati... more Polysulphone and spore-film UV-dosimeters compared to a UVI-monitoring instrument and two radiation transfer model systems-Evaluations for a UV-dosimetry study 2004 of preschool children___________________________ 6 UVEMA: A new project exploring degrading effects of UV radiation on materials__________________________________ 9 Standard MEAN Ultraviolet Radiation for non-Extreme Exposure Conditions: definition and indoor reproduction _______ 11 Calibration of UV radiometers is needed to guarantee the relevance of measurements ______________________________ 14 Solar simulators as a tool for assessing the impact of UV radiation on organisms and ecosystems _____________________ 17 Long-term measurements of UV-solar radiation in Dortmund (Germany) ________________________________________ 20 Analysis of UV-B solar radiation in C.I.B.A. laboratory, Spain ________________________________________________ 22 UV-B and UVI measured and calculated in Valladolid, Spain. _________________________________________________ 25 Realising a primary spectral irradiance scale on deuterium lamps in the ultraviolet_________________________________ 29 Comparison of measurement devices for the measurement of erythemal solar ultraviolet radiation during an outdoor-worker study in Austria ______________________________________________________________________ 31 Realization of a new commercial radiometer for measurement of the total UV effective irradiance of sunbeds ___________ 33 Investigation of comparison methods for UVA irradiance responsivity calibration facilities__________________________ 35 The use of a single-monochromator diode array spectroradiometer for UV-radiation measurements ___________________ 37 GaAsP trap detector for UV measurement _________________________________________________________________ 39 Characterization of integrating spheres for ultraviolet radiometry ______________________________________________ 41 Surveillance of UV-sensors in UV-disinfection plants in water works ___________________________________________ 42 Calibration and characterization of UV sensors for water disinfection ___________________________________________ 44 Monitoring of low-and medium pressure mercury lamps in UV-disinfection plants for drinking water _________________ 46 Improved entrance optic for global irradiance measurements with a Brewer spectrophotometer_______________________ 48 Time resolved measurements of spectral radiant flux from VUV to NIR (160 nm < λ < ≈ 1000 nm) on Xe excimer lamps ____________________________________________________________________________________ 49 Improvements of a fast scanning double monochromator for UV-B monitoring ___________________________________ 51 Long-term experience in using deuterium lamp systems as secondary standards of UV spectral irradiance ______________ 52 Expanded Measurement Uncertainty of Spectral Measurements Outside of the Laboratory __________________________ 54 UV-Monitoring at Outdoor Workplaces-A Base for Well-Balanced Health Prevention Regulations___________________ 56 Extreme UltraViolet Phototherapy ______________________________________________________________________ 59 Photobiological quality control in UV phototherapy _________________________________________________________ 61 Personal UV-monitoring in health prevention and risk analysis ________________________________________________ 62
A method for determination of the effective measurement plane of measuring heads with diffusers i... more A method for determination of the effective measurement plane of measuring heads with diffusers is presented. The method was tested with three commercial photometers and four spectroradiometer diffusers. The shifts of the diffuser reference planes were determined to be 5 – 9 mm and 0 – 7 mm, respectively. This effect causes measurement errors up to 3 % if the detectors are calibrated and used at different distances from the light source.
Microbridges, also known as microglows or micro-filaments, are miniature silicon filaments that a... more Microbridges, also known as microglows or micro-filaments, are miniature silicon filaments that are used e.g. in analysers as light sources. A microbridge is brought up to incandescence by passing an electrical current through it. Temperature determination of an operating microbridge with a contact measurement is complicated due to the small size of the bridge and the heat loss via the contact probe.