Advanced sensors and instrumentation systems are becoming increasingly important in the understanding, control and optimization of combustion processes across a wide range of industrial sectors. To bring together industrialists and academics to discuss the latest developments and trends in this particular area, the ISAT (Instrument Science and Technology) Group of the Institute of Physics organized a highly focused one-day technical meeting, which was held at the Rutherford Conference Centre at the Institute of Physics in London on 9 October 2002. The event was co-sponsored by the Combustion Physics Group of the Institute of Physics, the Institute of Energy, the Institute of Measurement and Control, the Institution of Electrical Engineers, the Coal Research Forum and Sira Ltd. The event was attended by 55 participants, 24 of whom were from industry.

The special feature in this issue (on pages 1099-1158) brings together a collection of some of the papers that were presented at the event. Technical topics covered, though wide ranging as reflected in part by the diversity of the papers, demonstrate recent developments in the fields and possible approaches that may offer solutions to a broad range of measurement problems.

Sensors and instrumentation systems are required at every stage of a combustion process from fuel injection through flames to combustion emissions. On-line measurement and quantitative characterization of fuels fed into a combustion process are required in many applications. For instance, on-line continuous sizing of pulverized fuels in coal-fired power stations has been desirable for many years. Carter and Yan describe a digital imaging based system that has been developed for the on-line continuous monitoring of fuel particle size distribution. Digital imaging techniques, as reported by Shao et al, have also been applied in the automotive industry to achieve quantitative characterization of diesel sprays. Advanced flame monitoring using digital imaging techniques is being widely explored. The paper entitled `Combustion monitoring using infrared array-based detectors' by Carter and Cross presents such an approach in which a simple imaging sensor combined with digital signal processing algorithms is used. `On-line combustion monitoring on dry low NO_x industrial gas turbines' by Rea et al describes the application of digital signal processing techniques to on-line continuous monitoring of combustion dynamics of a gas turbine at a leading power generation organization. The paper by Pal et al describes the recent development of fibre Bragg grating sensor-based devices and their potential applications to temperature monitoring of combustion processes. On-line monitoring of near burner slag deposition using a hybrid neural network system is reported by Tan et al. Monitoring and characterization of combustion emissions have been a topical subject in recent years. Johnson et al describe the challenges in the development of techniques to characterize particulate emissions from aircraft. When taking measurements using low-cost scaled down test facilities it can be difficult to maintain similar conditions to those found in the full-size set-up. Jermy et al report the problems encountered in `Operating liquid-fuel air blast injectors in low-pressure test rigs' and discuss strategies for maintaining continuity under scaled down conditions.

I hope you enjoy reading the papers and find them both interesting and informative. As guest editor, I would like to offer my sincere thanks and appreciation to all the authors, referees and publishing staff of Measurement Science and Technology for their contributions and support, which made this special feature possible.