An Offset Compensation Method With Low Residual Drift for Integrated Thermal Flow Sensors

A new offset compensation approach for integrated thermal flow meters is described. The method is based on micromachined differential flow sensing structures with the heater split into two identical and symmetrical sections. The power unbalance between the two heaters is used to compensate the intrinsic sensor offset. The effectiveness of the approach is proven by means of experiments performed on micro flow meters fabricated by postprocessing chips produced with a commercial microelectronic process. The tests were devoted to demonstrate the robustness of the offset compensation with respect to variation of both the gas temperature and type.