Micromachined structures for thermal measurements of fluid and flow parameters

In this paper thermal sensor-actuator structures are proposed that can be used to measure various fluid parameters such as thermal conductivity, flow velocity, heat capacity, kinematic viscosity and pressure. All structures are designed in such a way that they can be realized in the same fabrication process and therefore they can be easily combined in a single device. All structures are based on the principle of thermal measurements: resistive structures are used for both heating and temperature measurements. For accurate measurements the temperature coefficient of resistance (TCR) must be well known. Therefore, a special structure, which can be used for auto-calibration, was designed to measure the TCR. A first device containing structures for the combined measurement of flow velocity, thermal conductivity and TCR has been fabricated. Measurements show promising results.