MICROANEMOMETER FOR FLOW MEASUREMENT OF G ASES

A flow sensing system is presented and reviewed, which is based on a m icromachined silicon microanemometer. Its application to the determina tion of mass of std. volume flow of gases of variable temperature, pre ssure and composition is discussed and the new aspects of the develope d, underlying theory are summarized, especially for the heretofore non -existing composition compensation. A dynamic range of over 1000:1, wi th sensing uncertainties of the order of +/- 1% have been demonstrated . Studies of the sensor's performance after being exposed to entrained particulate matter, as well as to accelerated life tests have shown t hat the above data will hold for life times of over 20 years. Availabi lity of both the ''smart'', digital-output, fully compensated, develop mental versions as well as simple, analog-output, only temperature and pressure-compensated, mass-produced versions, enable the use of this new sensing technology in a wide range of applications.