Full text
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| Author(s): |
Roberto Jacobe Rodrigues
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 1999-09-14 |
| Examining board members: |
Rogerio Furlan;
Francisco Javier Ramírez Fernandez;
Luiz Otávio Saraiva Ferreira
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| Advisor: | Rogerio Furlan |
| Abstract | |
This work presents the design of a gas flow microsensor that was implemented by using silicon microelectronics technology. Its main features are a low power consumption (tens of mW) and the possibility of integration in flow microactuators. We adopted a calorimetric device with floating microfilaments and termoresistive sensor elements. Analytical and numerical modeling were developed and validated according to previous results. Also, the good agreement with experimental results obtained in this work shows the consistence of our design methodology. The distance between the central heater and the sensor elements was determined and resulted in the range of 120 µm. Also, we observed the need of using a heater temperature in the range of 100°C. A fabrication sequence and a test set up were defined. The microsensor was inserted in a tube with 3 mm of diameter and tested with nitrogen (0 500 sccm). The resistive sensor elements were connected to a external Wheatstone bridge. Characteristic curves, output voltage vs. flow, were obtained by using a commercial flow sensor for calibration. A good agreement was obtained in terms of normalized characteristics curves. Differences in the absolute voltage values, however, suggest that part of the filaments are in thermal contact with the substrate, what is probable due to both small thickness of the sacrificial oxide layer (o.6 µm) and stress in the polysilicon structures. (AU) | |