Diesel engine exhaust soot particle concentration measurement assembly comprises sensor with circular ion generator for charging soot particles and upstream of measurement electrode
An assembly measures the concentration of charged particles (9) in an exhaust gas as this flows through a pipe with a measurement electrode (4). The pipe has a circular ion generator (2) which charges passing particles and is upstream of the electrode. A field barrier (3) is between the ion generator and electrode. The field barrier comprises two grids (3.1, 3.2), the first of which is linked to a voltage source (17) and the second is linked to an ammeter. The assembly has a second array of three circular measurement electrodes (5.1-5.3) which are downstream of and measure the gas flow speed in conjunction with the first electrode (4). The ion generator has an outer electrode (7) and a further device (15) for measuring the flow of ions to the outer electrode. The voltage is capacitance-coupled to the measurement electrode (4) by a further electrode (8), grid (3.2) or the additional measurement electrodes (5.1-5.3). The assembly further incorporates deflector electrodes. An Independent claim is included for an operating process in which the ion generator receives a supply of pulsed direct current electricity or low-frequency alternating preferably high-voltage current.
