Compact ozone photometer based on UV LEDs

Abstract

In this paper we have demonstrated the feasibility of a compact autonomous sensor for continuous, in-situ monitoring of ambient ozone (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) from UAVs. The primary innovation in this sensor is the combination of newly available light emitting diodes (LEDs) operating in the ultraviolet (UV) spectral region with compact, low-power, sensitive data acquisition electronics. The advent of LEDs operating in the UV region overlapping the Hartley band (255-260 nm) [1] of absorption for ozone enables the development of a very compact and highly sensitive optical sensor that can monitor O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> concentration with good precision. A UV LED-based ozone sensor has many advantages over currently available technologies, which use the 254 nm emission line from mercury discharge lamps as sources. Attractive LED features include: (1) low beam divergence, allowing collimation for propagation over long distances, (2) high brightness, allowing for shorter optical path length and higher measurement rates than lamp-based sensors, (3) stable power output over long lifetime, (4) amplitude modulation by current, and (5) passive wavelength stabilization. Furthermore, the mercury lamp requires ~1 kV to initiate the discharge and exhibits power degradation over time.