Abstract: Differential pressure measurement devices, installations and methods are disclosed, the devices including a main body and retainer. The main body is characterized by a front portion having a substantially constant curvilinear flow facing front surface, a rear portion, and a substantially constant diameter portion between the front portion and the rear portion. The rear portion includes relatively larger and smaller diameter termini. The installation of this invention is maintained in a fluid flow containing conduit and includes a pipe section affixed between sections of the conduit. The device is concentrically located in the otherwise unobstructed flow path defined by the pipe section, with the device retainer downstream of all measurement ports, and obstructs fluid flow thereat to establish annular flow therearound having predictable characteristics.

Abstract: A calibration syringe is constructed like a single stage manual pump having a plunger. The input manifold has a duckbill valve that functions to maintain a fixed air flow rate through the syringe even with variable forces acting on the plunger. The duckbill valve has a pair of flexible lips which face upstream against the air flow. As a vacuum is formed inside the pump's input chamber, ambient air pressure closes the flexible lips. Thus, variable plunger forces creates a variable orifice inversely proportional to the plunger force. The result is a constant flow rate syringe.