DEVICE FOR MEASURING THE RADIATION OF BACTERICIDAL IRRADIATORS UNDER BACKGROUND LIGHTING CONDITIONS

Abstract

Research was conducted on the creation of a specialized UV radiometer for measuring bactericidal UV radiation with a wavelength of 254 nm under background sunlight conditions. The purpose of the work is: creation of an algorithm of schematic and technical solutions for the development of a specialized UV radiometer UVBV, for measuring bactericidal UV radiation with a wavelength of 254 nm, resistant to background radiation. As a result of the research, an algorithm of schematic and technical solutions for the development of the mentioned UV radiometer was created. In particular, the requirements for such devices were analyzed. A photodiode for a UV radiometer based on AlxGa1-xN has been developed, which has a current monochromatic sensitivity of 0.05 A/W at a wavelength of 254 nm and an absorption edge at a wavelength of about 290 nm. A preliminary electric circuit of the radiometer was developed, which showed unreliable data under sunlight up to 2000 lux, namely, it responded to solar radiation (up to 10 μW/cm2 in the absence of UV radiation). An improved electrical circuit for suppressing the effect of background lighting on the photo signal generated by the radiometer. Resistance to background illumination by sunlight is ensured by automatic gain control, which ensures fixation of the modulation operating frequency in the frequency range from 3 kHz to 2 MHz and prevents the addition of currents caused by optical interference in the low frequency range from the constant component to 3 kHz to the overall photo signal. It is shown that the proposed design stably compensates the current up to 15 mA, which is equivalent to the illumination created by light interference, about 20,000 lux. The device, under conditions of background illumination of the sensor by solar radiation, generates only 3-4∙10-2 μW/cm2 at illumination up to 20,000 lux and the absence of UV radiation. This makes it possible to use the proposed scheme for measuring the energy illuminance of UV irradiators in conditions of background illumination by the Sun. Further research involves the creation of a hardware capability to ensure the measurement of energy illumination created by a bactericidal irradiator with a wavelength of 254 nm under the conditions of its illumination by the Sun, which creates an illumination of 20,000 lux at a level of not less than 0.4 and not less than 0.1 μW/cm2. Solving this task will allow measuring the radiation of bactericidal lamps without additional expensive optical filters.