A single chip, double channel thermal flow meter

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 innovative aspect of the sensor is the use of a plastic adapter, thermally sealed to the chip, to convey the gas flow only to the chip areas where the sensors are located. The packaging approach allowed placing two micrometric differential thermal anemometers, present on 4 × 4 mm² silicon chips, into distinct flow channels. The reduced spacing between the sensing structures required positioning of the latter on channel bends, introducing sensitivity reduction and response asymmetries with respect to single channel devices presented earlier. These effects are explained using fluid-dynamic simulations.