Fluid flowmeter

Claim 1

Apparatus for measuring fluid flow through a main supply line, comprising: a. a restrictive element within said main line for developing a differential pressure proportional to the square of the velocity of the fluid; b. a shunt line connected to the main line to divert fluid from the main line at the higher pressure side of the element and to return the fluid to the main line at the lower pressure side of the element, said shunt line having a pressure drop thereacross which is proportional to the first power of the velocity of the fluid passing through said shunt line; c. a thermal connected in said shunt line, said flowmeter including: Claim 1 Continued 1. a conduit through which the diverted fluid passes; 2. means at spaced locations along the exterior of said conduit for sensing the temperature of the conduit at said locations and for producing output signals representative of the temperatures sensed; 3. means for heating a first portion of said conduit containing a first one of said temperature sensing means; 4. means for preventing a second portion of said conduit from being heated when said first portion is heated, said second conduit portion containing a second one of said temperature sensing means; 5. means responsive to the output signals produced by the temperature sensing means for varying voltage supplied to said heating means in order to maintain a constant difference in temperature between said first and second temperature sensing means; and Claim 1 Continued 6. indicating means responsive to the first power of the voltage supplied to said heating means to thereby provide a representation which is a function of the flow rate through said main supply line.