Jaroslav Stepanek

Comparison of light sources for household use due circadian effect

The aim of the paper is to compare of light sources for household use. These sources are compared due to content of blue light in their spectrum. Classical bulb, halogen bulb, linear fluorescent lamp and LED retrofits were used for spectrum measurement. It was used fluorescent lamp and LEDs with various colour temperature.

Laboratory high voltage capacitor with low PD level and low dissipation factor

High voltage capacitors are widely used in middle and high voltage laboratories and testing rooms. Capacitors are used for measurement of voltage in the form of voltage dividers. Injection and blocking capacitors are placed in the galvanic systems of partial discharges. And high voltage capacitors are also used in the high voltage as the part of laboratory bridge circuits. Common characteristics of these capacitors are the stability of parameters in time and voltage, low value of PD level. And usage as the capacitor with low value of dissipation factor (tan delta) for bridges. This paper is focused on the description of the parameters of these capacitors, their implementation and the function verification.

Visual angle in photobiological safety

This paper deals with theme of measuring of photobiological safety. For evaluating of photobiological safety is important determination of visual angle of source. Paper is describing effect of visual angle change on measured data. Visual angle was changed by changing of measuring distance and by changing of field stop diameter. All measurement was realized on double monochromator spectroradiometer.

The uncertainty of measurement of the luminous flux in an integrating sphere

This article has task to inform a reader of uncertainties of measurement in laboratory of light, especially in integrating sphere. In the first part there are mathematical descriptions of different types of uncertainties, including the methodology for their determination. The second part is focused on detailed description of particular standard uncertainties for measurement of the luminous flux in an integrating sphere. The last section provides practical calculations and results of standard uncertainties as a wavelength function.

Ecodesign of light sources

The aim of this paper is to determine the amount of materials which are used in the light sources construction. Another aim of this paper is to identify environmental demands in the production and disposal of light sources on the basis of the material composition.

Use of photometry in the field of high voltage

Laboratory testing of high voltage tested objects often leads to creation of discharges. Discharges are generated by breakdowns or flashovers outer insulation of the tested objects. These discharges generate emission in the IR, UV and also in the spectrum of light. The spectrum and intensity of radiation is dependent on the duration and level of passing current discharge. The shape, density and the spectrum of the discharge are also to some extent affected by the chemical composition of the gas surroundings, the electrode materials and the atmospheric pressure. The parameters of discharges are usually in HV laboratories specified by the measured time course of voltage and current passing through the discharge. An alternative is using of the analytical tools of lighting laboratory. Timing can be determined by using a fast photodiode. The chemical composition of the gas atmosphere and the electrode material affect the measured spectrum of light and UV. The average measured brightness value is dependent on the passing current of discharge and ambient gas pressure. The content of the article is focused on the application of some instruments from the filed of photometry to the high voltage measurement. This opens up new possibilities for the combination of these two disciplines and finding new possibilities of application.

Dependence of luminous flux on light source position

The aim of the paper is to find out how the luminous flux of fluorescent lamps depends on the change of the source position. Linear fluorescent lamps, compact fluorescent lamps and circular fluorescent lamps were used for measurement. Linear and circular fluorescent lamps were measured in the horizontal and vertical position, the compact fluorescent lamp was measured with the slot facing down, and facing up, and also in a horizontal burner position. Measurement of luminous flux was done in an integrating sphere.

Growth chamber illumination with a special luminaire

Article describes the design of lighting in growth chamber with low energy consumption. For this purpose we created a special luminaire that allows during different phases of plant life, regulate the spectrum of emitted energy and thereby effectively utilize light without wasting electricity. It is also important light intensity for proper growth of plants, respectively incident radiation. The paper discusses the directional characteristics of the luminaire and its spectral distribution which are an important part of the input data for the design lighting.