Wide range semiconductor flow sensors

Micromachined flow sensors based on thin film germanium thermistors offer h igh flow sensitivities and short response times. Using the controlled overt emperature scheme, the measurable air flow velocity ranges from +/-0.01 to +/- 200 m/s and the response time to large step changes of the air velocity is less than 20 ms. In the constant power mode, a signal rise time of 1.6 ms has been demonstrated by the application of shock waves. An air flow mea suring range from 0.6 ml/h to at least 150 l/h has been achieved, e.g. with a rectangular flow channel of 0.54 mm(2) cross-sectional area. Using a loo kup table transformation, a linearized output signal can be obtained within 25 mu s. (C) 2000 Elsevier Science S.A. All rights reserved.