BS ISO 15727:2020 pdf download – UV-C devices — Measurement of the output of a UV-C lamp
Magnetic ballasts are used to start the UV-C lamp and may be either standard electromagnetic or energy-efficient electromagnetic. The ballast provides a time-delayed inductive kick with enough voltage to ionize the gas mixture in the tube after which the current through the tube keeps the filaments energized. The starter will cycle until the tube lights up. While the UV-C lamp is on, a preheat ballast is just an inductor which at the main frequency (50 Hz or 60 Hz) has the appropriate impedance to limit the current to the UV-C lamp to the proper value. Ballasts shall be fairly closely matched to the UV-C lamp in terms of tube wattage, length, and diameter.
4.3.3 Electronic ballasts Electronic ballasts are basically switching power supplies, which eliminate the large, heavy, ‘iron’ ballast in favour of an integrated high frequency inverter/switcher. Current limiting is then done by a very small inductor, which has sufficient impedance at the high frequency. Properly designed electronic ballasts are relatively reliable, which depend on the ambient operating temperature, location with respect to the heat produced by the UV-C lamp as well as other factors.
5 Measurement of the output of a UV-C lamp
5.1 Measurement method classification
There are two methods to measure the output of a UV-C lamp: 1. Measurement of the output of a UV-C lamp in a darkroom: Tests in laboratory (also known as static darkroom test) are conducted to ensure the accuracy and consistency of the measured results; 2. Measurement of the output of a UV-C lamp in a test chamber: For industrial application, the tests in a test chamber shall take account of the impact of environmental changes in field (such as temperature change and air velocity change). This method is described in Annex B.
5.2 Measurement of the output of a UV-C lamp in a darkroom 5.2.1 Instrument The cosine correction for radiometers and spectroradiometers is critical to the proper measurement of the UV-C irradiance. The cosine correction shall be confirmed by the following method for each UV-C lamp and ballast combination so that the UV-C lamp measurements are consistent within and between laboratories. The minimum measurement distance needs to be determined for the given UV-C lamp and UV-C radiometer in order to verify cosine response characteristics of the UV-C radiometer and reduce its cosine correction error. The method is as follows:
a) Take readings of the UV-C radiometer for different distances (radiometer position perpendicular to the UV-C lamp axis), see Figure 4;
b) Take several readings of the UV-C irradiance. For example, moving the radiometer from the closest point to the most remote point and then back again;
c) Average the irradiance readings for each distance;
d) Calculate the output UV-C radiation power of the UV-C lamp from the measured irradiance using Formula (1) for each distance;
e) Calculate the output UV-C radiation power of the UV-C lamp; plot the calculated UV-C power versus the distance;
f) When the measurement distance is greater than the minimum distance D min , the measured UV-C irradiance is consistent with the UV-C output power through calculation as per Formula (1). The UV-C output power of the UV-C lamp should become independent of the distance;
g) The measurement distance shall be greater than D min . The distance derived by this method is valid for the combination of specific UV-C lamp length and specific individual radiometer.
5.2.2 Calibration In order to ensure the accuracy and reliability of the data issued by the laboratory, the laboratory shall meet the requirements of ISO/IEC 17025.
The following instruments shall be calibrated as per the standard method:
a) UV-C radiometer shall have valid and traceable calibration documents;
b) Calibration of the radiometer or the spectroradiometer shall comply with requirements of ISO/IEC 17025;
c) Power analyser shall have valid and traceable calibration documents.