Apparatus for use in the measurement of the flow rate of fluid flow

Apparatus for use in conjunction with a differential pressure sensitive transducer to measure the flow rate of a fluid flow, the apparatus comprising:

• a body which defines a duct through which the fluid flow to be measured is directed;
• at least one pressure fluid supply passage formed in the body and in communication with the duct, said at least one pressure fluid supply passage being adapted for connection to a source of fluid pressure so as to direct at least one jet of fluid under pressure across the duct;
• and
• a pair of receiver passages formed in the body and in communication with the duct opposite said at least one pressure fluid supply passage with which they are arranged symmetrically through respective mouths which are defined within a wall of the duct, each receiver passage having a pressure fluid tapping, the pair of pressure fluid tappings being arranged for connection to respective inlet ports of the differential pressure sensitive transducer when the apparatus is in use, said pressure fluid tappings being arranged so that the fluid pressure signal which each transmits to the respective inlet port of the differential pressure transducer when the apparatus is in use is a static fluid pressure signal which is representative of the static pressure of fluid flow at the respective point in the respective receiver passage;
• wherein the two receiver passages are connected together so as to define a loop by which the mouths communicate one with the other, the dimensions and configuration of that part of the loop between those points at which the static fluid pressure signals are derived being such as to ensure that fluid flow therewithin is laminar.

Apparatus for use in the measurement of the flow rate of a fluid flow, the apparatus comprising:

• a body which defines a duct through which the fluid flow to be measured is directed;
• a pair of pressure fluid supply passages formed in the body in communication with the duct, adapted for connection to a source of fluid pressure and orientated with respect to the duct so that, in use of the apparatus, the pair of supply passages directs a pair of jets of fluid under pressure across the duct, the axes of the two supply passages being convergent so that the jets meet part way across the duct, each supply passage having a pressure fluid tapping for sensing static fluid pressure therein;
• a pair of receiver passages formed in the body and in communication with the duct opposite the two supply passages with which they are arranged symmetrically through respective mouths which are defined within a wall of the duct, each receiver passage having a pressure fluid tapping;
• a fluidic differential amplifier device having
• a common supply input, connecting to a source of pressurized fluid,
• two opposed pressure inputs, each connecting with a respective one of the receiver passage pressure tappings;
• and
• two flow outputs, each connecting with a respective one of the supply passages, and controlled by the pressure inputs so that any change in the differential pressure between the two pressure inputs produces a change in the flow differential between the two flow outputs tending to equalize the pressures of the two pressure inputs;
• and
• a differential pressure sensitive transducer having a piar of fluid pressure input ports, each input being in communication with a respective one of the supply pressure tappings for producing a signal proportional to the difference in static pressure between the fluid flow in the two supply passages, said signal being proportional to the flow rate of fluid flow through the duct.