THERMAL MASS FLOW SENSOR

摘要

An apparatus for sensing a mass flow rate of a fluid in a thermal mass flow meter has a sensor tube. The sensor tube has a tube for carrying the fluid flow at the flow rate to be sensed. A temperature responsive member is disposed in good heat transfer relation with the tube. The temperature responsive member, when energized, produces at a sensor signal node a sensor signal responsive to the rate of mass flow of the fluid through the tube. The sensor signal is offset from a null signal condition by an unsymmetrical temperature distribution along the sensor tube when the mass flow rate of the fluid is zero. A means for modifying the temperature distribution along the sensor tube alters the unsymmetrical temperature distribution and causes the sensor signal node to produce a substantially null signal condition when the mass flow rate of the fluid through the tube is zero.