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This paper reviews solid-state gas sensing techniques that could be developed to supersede the NDIR bench and the electrochemical cell that are presently used in the majority of aftermarket emission analysers. Techniques considered include acoustic wave devices, chemfets, chemi-resistors and optical devices. Technical performance, e.g. sensitivity, selectivity, stability and speed of response, are assessed and compared. Manufacturability, cost, interfacing and processing requirements are also examined. The capability for inclusion in a hand-held analyser unit is the key consideration. Techniques that meet the review criteria are identified and recommendations are made as to requirements for further research and development.

This paper describes a novel “drive-on” RPM measurement system intended for use on Heavy Goods Vehicles (HGVs). The system transducer is a piezoelectric element placed under a drive wheel of the vehicle under test. The sensor responds to engine and suspension system vibrations and derives the RPM value from the vibration signature. This paper presents experimental data from the novel system and provides analysis and comment upon the results.