Microfabrication of a variable range and multi-directionally sensitive thermal flow sensor

• Published in: Sensors and actuators. A. Physical. Vol. 220; pp. 159 - 167
• Main Authors: Yarali, Milad, Khanna, Sanjeev K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2014
• Subjects: Air flow; Constants; Devices; Heating; Mathematical models; Micromechanics; Multi-range sensor; Sensors; Thermal flow sensor; Thermistors; Thin film thermistor; Titanium; Two-dimensional flow measurement; Thermal flow sensor; Thin film thermistor; Two-dimensional flow measurement; Multi-range sensor
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2014.09.008

•New micromachined thermal flow sensor with 12 thermistors.•Large range of flow measurement from 0.1 to 20m/s.•Multidirectional flow measurement. This investigation reports the design, fabrication and characterization of a variable range and multi-directionally sensitive micromachined thermal flow sensor based on amorphous germanium thermistors. For measuring various flow ranges and flow directions with a single device, 12 thermistors are placed on an 2mm×2mm supporting square shaped dielectric membrane made with silicon nitride. The thermistors are located at different optimized distances from a central micro-heater that is made with a bilayer of Ti/Pt and can be heated to 200°C with about 580mW applied power. The thermistors are laid as six pairs on the aforementioned substrate with three pairs located along the X-axis and another three pairs located along the Y-axis. The device was characterized in the presence of air flow velocities up to 20m/s and at constant heating power modes of 500mW and 250mW in order to measure the achievable flow speed and direction. Characterization results were compared with simulation results and the errors in flow speed and angle measurement have been discussed.