Ultra-High Range Ratio（＞10000:1） Thermal Mass Flowmeter

A high-performance mass flowmeter based on a microelectromechanical flow sensor chip is developed. To meet the requirements of high precision and wide range gas mass flowmeter in semiconductor, hydrogen energy, environmental protection and other industries, we broaden the range ratio of the flowmeter under the same level of accuracy. The sensor chip with a sensitivity of 0.192 mV/sccm and a detection limitation of 2.707×10^-3mL/min is obtained. In the device design, we demonstrate a dual-mode amplifier processing circuit and develop a miniature flow diverter to realize the wide range ratio of the mass flowmeter. The dual-mode amplifier processing circuit and the flow diverter are simulated and optimized. The flowmeter is tested and characterized in detail. The limit of detection(LOD) of this mass flowmeter is 0.659 mL/min. In the full scale range of 0.15%, the maximum detection flow is 100 slm and the minimum is 10 mL/min, which can achieve a range ratio of 10000∶1. The maximum relative error is 1.07% in the range of 0.1-100 slm and 3.6% in 0-100 mL/min, and the measurement results show good repeatability and stability.