Abstract: A thin metal diaphragm of a differential pressure unit (DPU) is stretched beyond its yield point. This method step unexpectedly reduces the spring rate and zero shifts due to line pressure fluctuations and due to differential thermal expansion and contraction between the diaphragm and its support. It also unexpectedly makes the DPU more accurate by allowing for a weaker and more accurate zero spring adjustment.

Abstract: A flowmeter and a function generator which may be employed separately or as an integral part of the flowmeter. A differential pressure unit (DPU) is connected to a pipeline on opposite sides of an orifice plate therein. The DPU produces an input shaft rotation directly proportional to the differential pressure. A linkage mechanism is then moved by the input shaft. The air relay produces an outlet air pressure which is substantially a curvilinear function (square root, for example) of the input shaft rotation. The curvilinear function is generated by the use of the linkage mechanism which includes plural fulcrums. These fulcrums are fixed to the air relay output shaft. A lever supported usually on each fulcrum in succession rocks on each successive fulcrum.