Abstract: A thermal, flow measuring device and method for measuring the flow of a measured medium. During a heating phase of predetermined length a constant heating current of a first electrical current source flows through a first resistor. During a first measuring phase of predetermined length a constant measurement current of a second electrical current source flows through the first resistor. During the first measuring phase a first voltage falls across the first resistor, wherein during a second measuring phase of predetermined length during the first measuring cycle the constant measurement current of the second electrical current source flows through a second resistor.
Abstract: A device for determining and/or monitoring volume and/or mass flow rate of a medium that flows in a direction of flow through a pipeline/measuring tube of inner diameter. The device comprises at least two ultrasonic transducers that emit and/or receive ultrasonic measuring signals along defined sonic paths and a control/evaluation device which determines the volume flow rate and/or the mass flow rate of the medium to be measured inside said pipeline/measuring tube based on the ultrasonic measuring signals according to the travel-time difference principle. In order to provide a multichannel ultrasonic flowmeter, at least one reflector element is placed in the interior of the pipeline/measuring tube. The reflector element has a defined distance from the inner surface of the pipeline/measuring tube and is placed within the sonic path of the ultrasound measuring signals running through the pipeline/measuring tube.