A LIQUID VELOCITY SENSOR-BASED ON THE HOT-WIRE PRINCIPLE

This paper reports on modeling and characterization of a silicon liqui d velocity sensor fabricated by using an industrial bipolar process co mbined with micromachining. For applications in the biomedical field, miniature sensors are needed for measuring flow velocities in the rang e up to 2 m/s. In order to measure such small velocities, we have deve loped a sensor which is sensitive to variations of a forced heat flow modulated by the liquid velocity. As a large temperature gradient will change the properties of biological liquids, this sensor uses small t emperature differences of about 1 to 10-degrees-C. A high average sens itivity of 10 mV/(m/s) has been measured. The overall dimensions of th e chip are 2.0 mm x 1.6 mm x 0.4 mm.