PURPOSE: To prevent air from entering into a chamber by providing a block between a transmitter body and high-pressure flange and by sealing the chamber by welding the block to the transmitter body.

CONSTITUTION: Diaphragms 3 and 4 are fitted to both flanks, and transmitter body 1 equipped with displacement detection mechanism 9 at its inside is provided with block 33 at the outside of diaphragm 4 applied with pressure from remote diaphragm mechanism 6. Link element 22 communicating with remote diaphragm mechanism 6 is linked to through hole 33a formed in the block 33, which is welded to the flank of body 1. This welding seals chamber 21 and even if negative pressure is applied to remote diaphragm mechanism 6, none of air is not permitted to enter into chamber 21 between body 1 and block 33.