Automatic compensation of pressure effects on smart flow sensors in the analog and digital domain

Two different approaches for the automatic compensation of pressure effects on thermal flow sensors are investigated. One approach operates in the analog domain and it is based on a closed-loop circuit that uses a pressure dependent signal to keep the sensor output constant. The digital approach operates in an open loop fashion and is capable of producing also a pressure reading. The effectiveness of the proposed methods has been verified by means of a smart flow sensor integrating on the same chip the sensing structures and a configurable electronic interface performing signal reading and non idealities compensation. The chip has been designed with a commercial CMOS process and fabricated by means of a post-processing technique. The experimental results performed in nitrogen confirm that both methods are capable of reducing the sensitivity of the flow sensor output signal to pressure variations.