A silicon micromachined flow sensor using thermopiles for heat transfer measurements

A silicon micromachined flow sensor composed of a platinum heater and four thermopiles surrounding the heater is described. Two of the four thermopiles placed up and downstream in the flow measure the amount of heat carried by the fluid, while the other two arranged perpendicular to the flow direction monitor, the heat transferred from the heater to the fluid. This architecture allows the normalization of output of the up and downstream thermopiles by the monitored output. Experimental results show that the normalization is quite useful for achieving a rangeability as wide as 1:1000 and also for reducing temperature and pressure dependence.