Microstructure sensors for flow, differential pressure and energy measurement

The point measurement of velocity of gaseous fluids has been made for some time with hot wire anenometer type sensors. We have developed a microflow sensor on sillicon which features a wide dynamic range (1-4000 feet/min), fast response (5 msec), low operating power (-10mW), and batch fabrication for reproducibility and cost effectiveness. Its small size and low power dissipation make it well sulted for a velocity sensor to indicate mass flow or differential pressure across a small orifice. Theoretical aspects of this approach and laboratory experiments to characterize the performance of this interesting microsensor are discussed. Safety test results are reported. We are also exploring the sensitivity of certain microsensors to variations in gas properties such as composition, gas density, specific heat, and viscosity. This sensitivity to gaseous fluid parameters might form a basis for the measurement of energy flow under advantageous conditions of automatic compensation for pressure and temperature changes. The Gas Research Institute sponsored part of this work involving correlations between various natural gas properties