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Screen

Belongs to:

Home

Synonyms:

Cathode-ray tube screen, Flat panel display, Flat screen, Monitor, PC screen, Plasma display panel, TV screen, Tube screen, Visual display terminal, Visual display unit

Description:

Measured values for both TV and PC screens can be found under "screen". As far as possible, they are distinguished acc. to the technology employed (e.g. cathode ray tubes, LCD screens). Flat screens are based on LCD or plasma technology; the employment of cathode ray tubes is not feasible due to space requirements.

For a tube screen, the central element is a cathode ray tube. During its thermic heating, electrons are emitted and deflected by a magnetic field of a certain frequency. In horizontal direction, the deflection frequency is 15.625 kHz, in vertical direction 50 Hz. Having hit the fluorescent screen, the electrons generate a light spot. Its brightness dependent on its position on the screen provides information about the image content. In order to depict a complete picture, all pixels are passed line-by-line.

In contrast to that, the main components of an LCD (Liquid Chrystals Display) screen are liquid crystals. Each pixel corresponds with a crystal. Its transparency can be controlled by a given voltage without influencing the adjacent crystals: Once a voltage has been employed, the crystals change their permeability for polarized light. The polarized light originates from a background illumination, followed by a polarization filter.

Frequency ranges:

• 50–60 Hz (for non-tube screens)
• 50 Hz–15.625 kHz (for tube screens)

Type of field:

electric and magnetic

Measurements (acc. to literature)

References

1. No authors listed (2019): [Radiation and radiation protection]
2. Leitgeb N et al. (2008): Electric emissions from electrical appliances
3. Behrens T et al. (2004): Quantification of lifetime accumulated ELF-EMF exposure from household appliances in the context of a retrospective epidemiological case-control study
4. Mader DL et al. (1992): Residential exposure to 60-Hz magnetic fields from appliances
5. Kurokawa Y et al. (2004): Evaluation of residential exposure to intermediate frequency magnetic fields
6. Preece AW et al. (1997): Magnetic fields from domestic appliances in the UK
7. Kim YS et al. (1997): Exposure of Workers to Extremely Low Frequency Magnetic Fields and Electric Appliances
8. Ainsbury EA et al. (2005): An investigation into the vector ellipticity of extremely low frequency magnetic fields from appliances in UK homes
9. Lacy-Hulbert A et al. (1998): Biological responses to electromagnetic fields
10. Preece AW et al. (1999): Assessment of Human Exposure to Magnetic Fields Produced by Domestic Appliances
11. National Research Council (NRC) (1997): Possible health effects of exposure to residential electric and magnetic fields
12. Leitgeb N et al. (2008): Magnetic emission ranking of electrical appliances. A comprehensive market survey
13. Moser M et al. (2006): [Non-ionizing radiation and health protection in Switzerland: basic information]
14. Van Den Bossche M et al. (2015): In situ exposure assessment of intermediate frequency fields of diverse devices
15. Farag AS et al. (1998): Electromagnetic fields in the home