Abstract: Apparatus for measuring a differential pressure of a fluid flowing through a fluid line includes a nozzle having a nozzle interior wall defining a nozzle chamber. The nozzle interior wall tapers at a constant rate of area reduction to generate a laminar fluid flow. A differential pipe is coupled to the nozzle and fluidly communicates with a downstream portion of the fluid line. The differential pipe has a pipe interior wall defining a differential chamber fluidly communicating with the nozzle chamber. A first pressure port is formed in the nozzle and fluidly communicates with the nozzle chamber to obtain a first gauge pressure of the fluid, and a second pressure port is formed in the differential pipe and fluidly communicates with the differential chamber to obtain a second gauge pressure of the fluid.