a transmitter provides an output that is indicative of pressure and has two modular transmitter bodies , one including a sensor , and the other having an isolator diaphragm with a substantially non - compressible fluid that transfers movement of the isolator diaphragm to the sensor . the bodies each have mating passageways to transfer non - compressible fluid from one body to the other and are assembled together using a ring of extrusile material disposed around the mating portions of the passageways to seal the passageways together when the transmitter bodies are assembled . the isolation fluid is filled in the passageway of the bodies before the first and second transmitter bodies are assembled . the assembly can be accomplished without complex procedures and still insure that accurate transmitter operation will be obtained .