Apparatus, systems, and methods of measuring relative pressure based on the displacement of a Cartesian diver are provided. Within the system, various designs of divers, as well as a variety of measurement methods implementing such systems and apparatus, are illustrated. The systems and methods described herein are directed to precise pressure measurements traceable to the SI through the vertical displacement of a ludion within a two fluid system. The system is selectively optimized to ensure the buoyancy and mass of the ludion as well as the density of the gases and fluids involved are known and controlled.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. A conduit contains a movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus is adjustable to have different threshold set points by adjusting the pivot arm inclination. The device may include at least two pivot axes. A rotating base may rotate relative to the barrier or wall, and a pivot arm may be attached and rotate relative to the rotating base. With the rotating base set at a first rotation angle, the pivot arm may be adjustable within a single plane. When the rotating base is set at a second rotation angle, the pivot arm may be adjustable within a different single plane. The device may include a single pivot axis where a pivot arm is parallel to the wall and rotates about a horizontal axis perpendicular to the wall.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. A conduit contains a movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus is adjustable to have different threshold set points by adjusting the pivot arm inclination. The device may include at least two pivot axes. A rotating base may rotate relative to the barrier or wall, and a pivot arm may be attached and rotate relative to the rotating base. With the rotating base set at a first rotation angle, the pivot arm may be adjustable within a single plane. When the rotating base is set at a second rotation angle, the pivot arm may be adjustable within a different single plane. The device may include a single pivot axis where a pivot arm is parallel to the wall and rotates about a horizontal axis perpendicular to the wall.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. A conduit contains a movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus is adjustable to have different threshold set points by adjusting the pivot arm inclination. The device may include at least two pivot axes. A rotating base may rotate relative to the barrier or wall, and a pivot arm may be attached and rotate relative to the rotating base. With the rotating base set at a first rotation angle, the pivot arm may be adjustable within a single plane. When the rotating base is set at a second rotation angle, the pivot arm may be adjustable within a different single plane. The device may include a single pivot axis where a pivot arm is parallel to the wall and rotates about a horizontal axis perpendicular to the wall.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. A conduit contains a movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus is adjustable to have different threshold set points by adjusting the pivot arm inclination. The device may include at least two pivot axes. A rotating base may rotate relative to the barrier or wall, and a pivot arm may be attached and rotate relative to the rotating base. With the rotating base set at a first rotation angle, the pivot arm may be adjustable within a single plane. When the rotating base is set at a second rotation angle, the pivot arm may be adjustable within a different single plane. The device may include a single pivot axis where a pivot arm is parallel to the wall and rotates about a horizontal axis perpendicular to the wall.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. An inclined conduit contains at least one movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus may include an on-board pitch indicator and a roll indicator which are used together to calibrate the apparatus and its installation. The apparatus may provide only one or more discrete number of pressure difference set points and be non-adjustable once installed. The inclined conduit may be non-rotatable relative to the baseplate, and the baseplate may be rotatable to change threshold pressure difference set points. The apparatus may provide a tamper-resistant indication of whether a threshold pressure differential is present.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. An inclined conduit contains at least one movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus may include an on-board pitch indicator and a roll indicator which are used together to calibrate the apparatus and its installation. The apparatus may provide only one or more discrete number of pressure difference set points and be non-adjustable once installed. The inclined conduit may be non-rotatable relative to the baseplate, and the baseplate may be rotatable to change threshold pressure difference set points. The apparatus may provide a tamper-resistant indication of whether a threshold pressure differential is present.

A transducer baseplate includes a base, a protrusion extending from the base along a longitudinal axis, a pair of opposed transducer receptacles defined within the protrusion, and respective pressure plena. The pressure plena are separated by a plenum wall, each plenum being in fluid connection with an area external to the protrusion through a respective pressure line. The pressure lines provide a direct fluid path to their respective receptacles.

A transducer baseplate includes a base, a protrusion extending from the base along a longitudinal axis, a pair of opposed transducer receptacles defined within the protrusion, and respective pressure plena. The pressure plena are separated by a plenum wall, each plenum being in fluid connection with an area external to the protrusion through a respective pressure line. The pressure lines provide a direct fluid path to their respective receptacles.

Methods and apparatuses for indicating the presence of a threshold directional differential pressure between separated adjacent spaces. A conduit contains a movable element that indicates whether the pressure difference between the two spaces is at least as high as a threshold pressure difference. The apparatus is adjustable to have different threshold set points by adjusting the pivot arm inclination. The device may include at least two pivot axes. A rotating base may rotate relative to the barrier or wall, and a pivot arm may be attached and rotate relative to the rotating base. With the rotating base set at a first rotation angle, the pivot arm may be adjustable within a single plane. When the rotating base is set at a second rotation angle, the pivot arm may be adjustable within a different single plane. The device may include a single pivot axis where a pivot arm is parallel to the wall and rotates about a horizontal axis perpendicular to the wall.