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Experimental Characterization of a Thermopile with Aluminum-n-type Polysilicon Junctions as a Base for Multi-directional Flow Sensor Implemented in a Silicon Chip
Muh. Thamrin1, Ayub Subandi2, Irman Idris2,3 & Adang Suwandi Ahmad2,3
1Dept of Physics University of Mulawarman, Jl. Barong Tongkok No.4 Kampus Gn. Kelua, Samarinda 75123.
2Microelectronic Center, ITB, Jl. Ganesha No.10, Bandung 40132.
3School of Electrical Engineering and Informatics, ITB, Jl. Ganesha No.10, Bandung 40132.
Email : muh_thamrin33204012@yahoo.com
Abstract. A multi-directional flow sensor has been realized. The essential part of the considered sensor is a thermopile configuration, which enables the measurement of the flow speed and the flow direction. The thermopile is a series arrangement of eight thermocouples. A thermocouple converts a difference in temperature into an electrical signal, by means of the Seebeck effect. The thermocouples are made of aluminum-N-type polysilicon junctions. The incoming flow is heated and the degree of heat transfer by convection to the flow, depends on the speed of the flow; the faster the flow the smaller the heat transfer, which leads to a smaller (Seebeck) output voltage of the thermopiles. After signal conditioning - i.e., filtering and amplification by means of an amplification system - the electrical output signals of the thermopiles are further signal-processed by applying analog-to-digital signal conversion, so that finally the flow speed and flow direction can be properly displayed on a computer screen. The measured values of the thermopower were in the range of: 0.433 mV/K to 0.6754 mV/K, which are in good agreement with the values found in the literature: 0.5 to 0.7 mV/K. In addition it was found that the flow speed
U is proportional to the reciprocal value of the square root of the output voltage of the outgoing thermopile.
Keywords: flow sensor, thermopile, Seebeck effect
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