Method and apparatus for overrange protection of the transducer in a differential pressure transmitter

摘要

A method and apparatus for protecting the transducer in a liquid- filled differential pressure transmitter having stroke limited, isolation diaphragms from exposure to overrange pressure are disclosed. Bidirectional overrange pressure protection is provided through the use of a single, preloaded bellows that is restrained by a preloaded stop means preferably including a preloaded mechanical spring. The bellows remains stationary when the differential pressure transmitter is exposed to a normal, operational differential pressure. When an overrange pressure is applied to the transmitter, the bellows expands or contracts to accommodate the liquid displaced by either of the isolation diaphragms thereby protecting the transducer from the overrange pressure. Upon removal of the overrange pressure condition, the protection apparatus automatically resets itself.