Constant power operation of a two-dimensional flow sensor using thermal sigma-delta modulation techniques

To compensate for ambient-temperature drift two-dimensional thermal flow sensors are typically heated to a constant temperature above ambient temperature. This operating mode requires all extra sensor to measure ambient temperature. It shown that similar compensation may be obtained by maintaining the sensor's heating power constant; thus eliminating the need for the ambient-temperature sensor. Constant power operation may be achieved by a simple electronic interface consisting of true thermal sigma-delta modulators. These control the distribution of heat in the sensor such that flow-induced temperature gradients are cancelled. The bit-stream output of the modulators then represents the (flow-dependent) heat distribution in the sensor. Flow speed and direction may then be determined from the decimated bit-streams.

[1]  Johan H. Huijsing,et al.  Design of thermal sigma-delta modulators for smart thermal sensors , 1995, Proceedings of ISCAS'95 - International Symposium on Circuits and Systems.

[2]  B. W. Oudheusden,et al.  The thermal modelling of a flow sensor based on differential convective heat transfer , 1991 .

[3]  Johan H. Huijsing,et al.  An electronic wind meter based on a silicon flow sensor , 1990 .

[4]  K. Toda,et al.  Simple temperature compensation of thermal air-flow sensor , 1996 .

[5]  Kofi A. A. Makinwa,et al.  A wind-sensor with integrated interface electronics , 2001, ISCAS 2001. The 2001 IEEE International Symposium on Circuits and Systems (Cat. No.01CH37196).

[6]  Kofi A. A. Makinwa,et al.  A wind-sensor interface using thermal sigma delta modulation techniques , 2001 .

[7]  Louis Vessot King,et al.  On the Convection of Heat from Small Cylinders in a Stream of Fluid: Determination of the Convection Constants of Small Platinum Wires, with Applications to Hot-Wire Anemometry , 1914 .

[8]  M. Elwenspoek,et al.  A new class of thermal flow sensors using /spl Delta/T=0 as a control signal , 2000, Proceedings IEEE Thirteenth Annual International Conference on Micro Electro Mechanical Systems (Cat. No.00CH36308).

[9]  B. W. van Oudheusden.  Integrated silicon flow sensors , 1989 .

[10]  Eugeniusz Prociow,et al.  Analysis of an ambient temperature influence on the thermal thin-film microsensor , 1994 .

[11]  Henry Baltes,et al.  Two-dimensional integrated gas flow sensors by CMOS IC technology , 1995 .