Abstract: A pressure transmitter has a pressure transducer in a transmitter housing. The transmitter housing includes a groove or a notch defining a flexure closely proximate a housing outer rim. The outer rim receives a large clamping force from a flange and is deflectable about the flexure for reducing transmission of axial and radial components of the clamping force from the housing outer rim to the transducer, which forces can cause distortions to the pressure transducer. Unevenly distributed clamping forces caused by differential thermal expansion of the flange, bolts and housing, are isolated from the transducer thereby reducing measurement errors. Further, transmission of hysteretic radial forces from the transmitter housing to the transducer caused by friction when the flange slides across the pressure transmitter housing, each having different thermal coefficients of expansion, is also reduced.

Abstract: A transmitter that provides an output indicating pressure difference between a line pressure and atmosphere outside the transmitter is made intrinsically safe by coupling the sensor cavity as well as other cavities where ignition can occur to atmosphere only through flame quenching paths. The opening in the transmitter housing in which the sensor is mounted has a plug including a sensor cavity that holds the sensor, and a fitting which is couplable to the pressure line. An isolator is used for transmitting the process pressure to the sensor through an isolator diaphragm acting on an incompressible filling the sensor cavity and transmitting pressure through a hole that is shaped to provide a flame quenching path. The passageway flame isolates the sensor from the process fluid line. The opposite side of the sensor is connected to atmosphere only through paths which are flame quenching because of the passageway shape.