UV Fluorescence

The measurement of sulfur dioxide (SO2) is based on the principle that SO2 molecules absorb ultraviolet (UV) light and become excited at one wavelength, then decay to a lower energy state, emitting UV light at a completely different UV wavelength.

The emitted UV fluorescence light passes through another bandpass filter, allowing only the signal from the SO2 molecule to reach the photomultiplier tube (PMT), which converts the pulsating signal into SO2 concentration. The light is directly proportional to the SO2 concentration present in the gas sample.

A reference detector continuously monitors the pulsing emission from the UV light source (a zinc lamp), compensating for the fluctuations in lamp intensity and ensuring a consistent and stable reading.

To prevent interference from emissions from other molecules present in the gas stream, the UV spectral region was specifically chosen to minimize any signals from gases present that would quench the SO2 signal.

In particular, when analyzing SO2 in combustion gas emissions it is necessary to use a hydrocarbon “kicker” to prevent interference and quenching from polycyclic aromatic hydrocarbons (PAHs) such as naphthalene. The Servomex SERVOPRO SO2 analyzers are equipped with such a “kicker”, ensuring a reliable, accurate reading all the time.

Products featuring Servomex UV Fluorescence technology:

  • SO2


    For industrial applications that require ultra-low emissions monitoring of sulfur dioxide

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