UV Photometry Analyzer
Working principle:
UV photometry is based on the absorption of radiation in the spectral range from 200 nm to 400 nm. In this field, a number of important industrial gases have distinct absorption bands.
The advantage of this gas analysis is that the measurements are not interfered with by vapors and carbon dioxide. In addition, these absorption bands show high absorption behavior and therefore can also be reliably detected at very low gas concentrations (<< ppm). In UV spectrometers, UV light-emitting diodes are chosen, whose emission wavelengths correspond spectrally to the corresponding absorption bands. This means that no other spectrometer or filter is required. This type of UV photometry is called non-dispersive UV method, also known as NDUV.
Basic structure:
The UV-LED radiation is split into a measurement and a reference path through a beam splitter. The reference beam reaches the detector directly, which converts it into a reference voltage value. Using this reference signal, the aging effect of the UV-LED is almost completely compensated. The measurement beam enters the cuvette, where the gas in the cuvette is absorbed by the radiation therein. The absorption behavior is recorded by the measurement detector and used to calculate the concentration of the gas in the measuring cuvette. The UV spectrometer is designed in such a way that the radiation components from several UV LEDs can also be coupled into the photometer. This means that multiple gases can be determined simultaneously by the UV spectrometer.
The measurement of nitrogen monoxide (NO) requires a selective UV radiation source in the spectral range around 226nm. For this purpose a gas discharge lamp filled with NO is used, which emits precisely the radiation that is required for the NO measurement. In this context, one speaks of resonance absorption. The process also referred to as UVRAS (UV Resonance Absorption Spectrometry).
Measuring gas and range:
vSulfur dioxide(SO2): 0 ~ 50ppm up to 10%(Vol)
vNitric oxide(NO): 0 ~ 300ppm up to 5,000ppm
vNitrogen dioxide(NO2): 0 ~ 50ppm up to 5,000ppm
vOzon(O3): 0~ 10ppm up to 5,000ppm
vChlorine(Cl2): 0 ~ 500ppm up to 30%(Vol)
vHydrogen sulfide(H2S): 0 ~ 100ppm up to 5,000ppm