  The fabrication and experimental characterization of a thermal flow meter,
capable of detecting and measuring two independent gas flows with a single
chip, is described. The device is based on a 4 x 4 mm2 silicon chip, where a
series of differential micro-anemometers have been integrated together with
standard electronic components by means of postprocessing techniques. The
innovative aspect of the sensor is the use of a plastic adapter, thermally
bonded to the chip, to convey the gas flow only to the areas where the sensors
are located. The use of this inexpensive packaging procedure to include
different sensing structures in distinct flow channels is demonstrated.
