초록 ▼

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. Meas

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.

대표청구항 ▼

An improved flow meter comprising, in combination, sensor tube means for permitted flow of a fluid to be measured to be passed therethrough; fluid flow sensing means having electrical sensing resistance means operatively wound around said sensing tube to form two resistive sensing coils at adjacent

An improved flow meter comprising, in combination, sensor tube means for permitted flow of a fluid to be measured to be passed therethrough; fluid flow sensing means having electrical sensing resistance means operatively wound around said sensing tube to form two resistive sensing coils at adjacent locations disposed along said sensor tube means for determining the fluid flow characteristics of a fluid flowing therein; the improvement comprising: non-woven, polyester fiber insulation tape means wrapped tightly around said sensor tube means and said two resistance sensing coils for improved thermal insulation, for significantly reducing external thermal heat loss, for more securely holding said two resistive sensing coils against the outer surface of said sensor tube means, for greater physical strength, for preventing convection of air proximate said two resistive sensing coils thereby eliminating attitude sensitivity, for improved isolation from the surrounding temperature ambient, and for increasing the sensitivity of said electrical sensing resistance means; and metallic thermal shield means having a high thermal conductivity and operably disposed concentrically around said insulation tape means for providing a homogeneous temperature distribution at the outer surface of said insulation tape means and in proximate contact with said non-woven polyester fiber insulation tape means for providing a homogeneous temperature distribution at the outer surface of said insulation tape means for substantially eliminating disturbances caused by radiation and conduction which can effect the accuracy of the sensor output in a non-symmetrical manner, said non-woven, polyester fiber insulation tape means further including solid plastic microspheres dispersed throughout said non-woven polyester fiber insulation for increasing thermal isolation from the surrounding temperature ambient and between adjacent resistive sensing coil windings, for increasing the strength and flexural support thereof, and for further lowering the thermal conductivity of said insulation tape means.