Abstract: A gas meter gas a conduit for passage of a gas flow; an ioniser arranged to ionise the gas flow in the conduit; a modulating electrode structure arranged for modulating the ion distribution in the ionised gas flow; and at least a detecting electrode structure downstream of the modulating electrode structure arranged for detecting the modulated ion distribution in the ionised gas flow. The modulating electrode structure is arranged downstream of the ioniser and is configured to generate an electrical field which is substantial in a parallel to the direction of the gas flow.

Abstract: A gas meter comprises a conduit (1) for passage of a gas flow A and an ioniser (2) arranged to ionise the gas flow in the conduit (1). A modulating electrode structure (4) downstream of the ioniser modulates the ion distribution in the ionised gas flow. A first detecting electrode structure (8) and a second electrode structure (9) downstream of the modulating electrode structure 4 detect the modulated ion distribution in the ionised gas flow. The modulating electrode structure (4) and the detecting electrode structures (8, 9) can be configured to generate an electrical field having at least a substantial component parallel to the direction of the gas flow. The modulating electrode structure (4) and the detecting electrode structures (8, 9) can comprise a pair of electrodes (5, 6, 10, 11), each having a plurality of apertures defined therein for passage of the gas flow.