Abstract: A method of monitoring functional capability of a soot sensor that is responsive to deposition of soot from an exhaust gas stream on a sensor surface comprises acquiring a measurement signal of the soot sensor and running a plausibility check, in which it is ascertained whether the measurement signal agrees with an expected finding. According to the invention it is detected whether conditions are present, on which liquid, e.g. water, from the exhaust gas stream condensates on the sensor surface. Additionally or alternatively, such conditions are produced. The plausibility check then includes ascertaining whether the measurement signal reflects the condensation of liquid. The detection of presence of conditions for condensation comprises a measurement or an estimation of temperature on the sensor surface.

Abstract: Method for measuring a fluid flow, in particular an air flow (L), flowing in a flow canal to an engine (VM) or from an engine (VM), by means of a fluid mass measuring means (3) connected to an evaluation means (2), wherein in a regularly performed cycle an operational parameter (D1, D2, . . . , Dn) characterizing the operating status of the engine (VM) is recorded, the data (M1, M2, . . . , Mn) supplied by the fluid mass measuring means (3) are recorded, at least one extreme value (Ep, En) is determined from the data (M1, M2, . . . , Mn) recorded since the beginning of a time period (t1, t2, . . . , tn), an average value (Wma) is determined from the recorded data (M1, M2, . . . , Mn), a pulsation amplitude (P1, P2, . . . , Pm) is determined by dividing the extreme value (Ep) by the average value (Wma), and the average value (Wma) is corrected by multiplying it by a correction factor (K11, K12, . . . , Kmn) which is selected in dependence on the operational parameter (D1, D2, . . .