Low cost PCB thermal sigma-delta air flowmeter with improved thermal isolation

A new low cost PCB solution for airflow metering is presented. The structure has been designed to increase the sensor bandwidth while keeping a total low cost of the sensor and its electronics. Two silicon dice are used: one in the cold point (a temperature sensor) and another in the hot point (a heater and a temperature sensor). The dice are directly placed on top of small Pyrex structures, which provide the necessary thermal isolation between the hot and cold points of the sensor, as well as with the outer environment. The time constant of the sensor is approximately 1 s. The sensor works in the closed loop mode, controlled by a thermal sigma-delta modulator. Airflow velocities down to 0.1 m/s can be measured.