A tubing ring formed in the vertical plane is pivoted at its central axis, and the pressure differential rotates this ring. The opposing torque is developed by a weight attached to the ring as shown below:
Depending on the reference pressure used, it can detect absolute or near atmospheric pressures. Although the housings can withstand up to 6000 PSIG (41 MPa), the pressure differential between reference and process pressure should be below that limit, which would cause the sealing fluid to be blown out.
These meters have been widely used in Europe but have found limited acceptance in the United States. Their application and operating principles are the same as those of the inverted bell meters. A tubing ring formed in the vertical plane is pivoted at its central axis, and the pressure differential rotates this ring. The opposing torque is developed by a weight attached to the ring.
Depending on the design and the filling fluid used, the minimum span for these units is 0.2 in. H2O (0.05 kPa) and the maximum span is 500 in. H2O (125 kPa). Depending on the reference pressure used, it can detect absolute or near atmospheric pressures. Although the housings can withstand up to 6000 PSIG (41 MPa), the pressure differential between reference and process pressure should be below that limit, which would cause the sealing fluid to be blown out. Also at high pressures, the flexible connections at the sensing lead become a source of errors and require constant maintenance.
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Instrumentation Basics 