MEMS flow sensor based on a sigma-delta modulator embedded in the thermal domain

A system for gas flow measurement, based on MEMS flow sensing microstructures and a sigma-delta interface, is described. The sensing structures consist of double-heater differential microcalorimeters, obtained by means of a post-processing procedure applied to chips fabricated using the Bipolar-CMOS-DMOS process BCD6s of STMicroelectronics. Part of the sigma-delta modulator is implemented in the thermal domain by exploiting the versatility of the double-heater sensing structures. The measurements performed in nitrogen flow prove the effectiveness of the proposed approach.