Method and apparatus for the measurement of volumetric flowrate in pipes and ducts

Claim 1

An apparatus for the measurement of the volumetric flowrate in a duct having a throttle device therein; said apparatus comprising: a first and a second pressure device for measuring pressure; means connecting said first pressure device upstream of the throttle device; means connecting said second pressure device at said throttle device; said first pressure device being operable to measure a pressure p 1 and said second pressure device being operable to measure a pressure p 2 ; a first signal converter connected to said pressure devices for producing a first electric signal representative of the pressure p 1 ; a second signal converter connected to said pressure devices for producing a second electric signal representative of the pressure difference p 1 -p 2 , lead means for connecting said first and second converters to a computer to apply said first and second electric signals thereto, said computer being of the type for producing a signal F according to the relation F=A(p.sub.1 -p.sub.2) + B(p.sub.1 -p.sub.2).sup.n + C(p.sub.1 -p.sub.2).sup.n · p.sub.1 + D wherein A, B, C and D are empirically determined constants that vary according to the shape and size of the duct, and n is substantially 0.5 but may be determined by means of a regression statement; and limiting means between said first converter and the computer for limiting the value p to a value not exceeding the pressure which corresponds to a completely filled duct.

Claim 2

An apparatus for the measurement of the volumetric flowrate in a duct having a throttle device therein; said apparatus comprising: a first and a second pressure device for measuring pressure; means connecting said first pressure device upstream of the throttle device; means connecting said second pressure device at said throttle device; said first pressure device being operable to measure a pressure p 1 and said second pressure device being operable to measure a pressure p 2 ; a first signal converter connected to said pressure devices for producing a first electric signal representative of the pressure p 1 ; a second signal converter connected to said pressure devices for producing a second electric signal representative of the pressure difference p 1 -p 2 , lead means for connecting said first and second converters to a computer to apply said first and second electric signals thereto, said computer being of the type for producing a signal F according to the relation F=A(p.sub.1 -p.sub.2) + B(p.sub.1 -p.sub.2).sup.n + C(p.sub.1 -p.sub.2).sup.n · p.sub.1 + D wherein A, B, C and D are empirically determined constants that vary according to the shape and size of the duct, and n is substantially 0.5 but may be determined by means of a regression statement; and limiting means between said first converter and the computer for limiting the value p to a value not exceeding the pressure which corresponds to a completely filled duct.