THERMAL FLOW METER HAVING DIAGNOSTIC FUNCTION

A thermal, flow measuring device for determining and/or monitoring the mass flow (φM) and/or the flow velocity (vF) of a flowable medium through a pipeline, comprising at least three sensor elements and an electronics unit, as well as method for operating a thermal, flow measuring device. Each sensor element is at least partially and/or at times in thermal contact with the medium, and includes a heatable temperature sensor. The electronics unit is embodied to heat each of the three sensor elements with a heating power, to register their temperature, to heat at least two of the at least three sensor elements simultaneously, continuously to ascertain the mass flow (φM) and/or the flow velocity (vF) of the medium, and, simultaneously, from a pairwise comparison of the temperatures and/or heating powers, to provide information concerning the state of at least one of the at least three sensor elements, and in the case that a malfunction and/or a deposit occurs on at least one of the at least three sensor elements, to perform a correction of the measured value for the mass flow (φM) and/or the flow velocity (vF) and/or to generate and to output a report concerning the state of the at least one sensor element.