Experimental Study of an Aluminum-Polysilicon Thermopile for Implementation of Airflow Sensor on Silicon Chip

Ayub Subandi, Irman Idris, Adang Suwandi Ahmad


A multi-directional airflow sensor has been realized. The essential part of  the  considered  sensor  is  a  thermopile  configuration,  which  enables  the measurement  of  flow  speed  and  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 the flow direction can be properly displayed on a computer screen. The measured values of the Seebeck coefficient or thermopower (S) were in the range of: 0.43 to 0.68 mV/K which are in good agreement with the values found in the literature: 0.5 to 0.7 mV/K. Moreover, it  was found that the  flow speed  U is  proportional  to  the  reciprocal  value  of  the  square  of  the  output voltage of the outgoing thermopile.

Full Text:



Makinawa, K.A.A. & Huijsing, J.H., A Smart Wind-Sensor Using Time Multiplexed Thermal Delta Modulation, ESSCIRC, pp.460-463, 2001.

Oudheusen, B.W. van & Huijsing, J.H., An Electronic Wind Meter Based on a Silicon Flow Sensor, J. Sensors & Actuators, A21-23 p420-424, 1990.

Incropera, F.P. & DeWitt, D.P., Heat and mass transfer, 5th ed., J. Wiley & Sons, N.Y., 2005.

Smith, R.A., Semiconductors, 2nd ed., Cambridge University Press, 1978.

Nolas, G.S., Sharp, J. & Goldsmid, H.J., Thermoelectrics, Basic Principles and New Materials, Springer-Verlag, B. Heidelberg, 2001.

Chang Liu, et.al., A Micromachined Flow Stress Sensor based on Thermal Transfer Principle, J. Microelectromechanical Systems, Vol. 8, No. 1, 1999.

Okulan, Nikan, A Pulse Mode Micromachined Flow Sensor with Temperature Driff Compensation, IEEE Transction on Electron Device, 47(2), 2000.

Balters, Hendry, Proceeding of the IEEE, 86(8), 1998.

Oudheusden, B.W. van, Integrated Thermopile Sensors, J. Sensors and Actuators, A21-23, p. 621-630, 1989.

DOI: http://dx.doi.org/10.5614%2Fitbj.eng.sci.2007.39.2.2


  • There are currently no refbacks.