Thermal gas mass flowmeter measures flow based on principle of convection heat transfer. Based on traditional design methods which are constant temperature difference type and constant power type

present a thermal gas mass flowmeter based on adjustable constant current source technology. Range of 0. 2

20 m / s

which is divided into three stages. At the first stage 0. 2

0. 9 m / s

heating current is set 40 m A

at the second stage 0. 9

1

0 m / s

heating current is set 60 m A

at the third stage 10

20 m / s heating current is set 80 m A. Calculation model for the whole range can be determined by summarizing the measurement data under the heating current. Tested on

large diameter airflow standard device in the discharge Laboratory of Tianjin University

system with pipe diameter200 mm achieve precision of 1 % and range ratio of 100∶ 1.