Improved flow meter

摘要

An improved mass flow meter is disclosed for measuring the flow rate of a fluid through a thin walled sensor tube that has the feature of high sensitivity to the temperature of the fluid within the sensor tube. The sensor tube is wound with closely coupled resistance elements of insulated wire. Measurement is accomplished with a conventional bridge connection to the sensor resistance elements. The bridge is designed to remain in balance over a wide range of ambient temperature at a zero flow rate. Fluid flow through the sensor tube upsets the uniform temperature gradient with heat loss being greater upstream so that the balance of the sensor resistance elements installed or coupled to the sensor tube (which elements are heated by a power supply) is progressively upset with increasing flow. External heat loss is reduced (thereby providing greater temperature sensing ability) by surrounding the sensor tube with a polyester fiber insulating material covered with a metallic heat shield and by connecting the flow meter into the fluid stream through thermal insulating couplings.