A measuring system for detecting pressure and/or density, having at least one process connector, a diaphragm, a measuring unit, a housing and a display, wherein a process pressure acts via the process connector on the diaphragm and the measuring unit converts a stroke of the diaphragm caused thereby into a rotational movement of a pointer when the process pressure is changed via the measuring unit, and the pointer on the display shows the pressure applied on the diaphragm on a scale. The measuring system includes a connecting piece which includes the process connector, a meter base and a tubular extension.

An air compressor having a pressure gauge, the pressure gauge contains: a hollow tube, a drive element, an anti-leak spring, a resilient element, and a cap. The hollow tube includes an accommodation chamber, a connector having a conduit, and a display unit. The drive element includes a protection unit, a first open segment, a second distal segment, a receiving portion, a hollow extension, and a protrusion. An anti-leak spring is received in the hollow extension of the drive element and abuts against the protrusion and the protection unit. The resilient element is received in the receiving portion. The cap includes a seat, a push bolt, and multiple passages. The accommodation chamber has a first fixing section and a second fixing section, a diameter of which is different from that of the first fixing section. The hollow tube further includes a tilted surround section and at least one discharge orifice.

An air compressor having a pressure gauge, the pressure gauge contains: a hollow tube, a drive element, an anti-leak spring, a resilient element, and a cap. The hollow tube includes an accommodation chamber, a connector having a conduit, and a display unit. The drive element includes a protection unit, a first open segment, a second distal segment, a receiving portion, a hollow extension, and a protrusion. An anti-leak spring is received in the hollow extension of the drive element, a first end of the anti-leak spring abuts against the protrusion, and a second end of the anti-leak spring contacts with the protection unit. The resilient element is received in the receiving portion of the drive element. The cap includes a seat, a push bolt, and multiple passages. An end of the resilient element contacts with the cap.

An air compressor having a pressure gauge, the pressure gauge contains: a hollow tube, a drive element, an anti-leak spring, a resilient element, and a cap. The hollow tube includes an accommodation chamber, a connector having a conduit, and a display unit. The drive element includes a protection unit, a first open segment, a second distal segment, a receiving portion, a hollow extension, and a protrusion. An anti-leak spring is received in the hollow extension of the drive element, a first end of the anti-leak spring abuts against the protrusion, and a second end of the anti-leak spring contacts with the protection unit. The resilient element is received in the receiving portion of the drive element. The cap includes a seat, a push bolt, and multiple passages. An end of the resilient element contacts with the cap.

A display structure of a pressure gauge of an air compressor, the air compressor is received in an accommodation box, and a scale portion of the pressure gauge is viewable via a displaying opening of the accommodation box, the pressure gauge includes a cylindrical body which is transparent and is formed in a pen shape, and the pressure gauge includes a colored O-ring configured to indicate a pressure value of the scale portion. The scale portion is not printed on the cylindrical body of the pressure gauge and includes a transparent panel on which the pressure value of the scale portion is marked on an internal face of the transparent panel, and the internal face faces the cylindrical body of the pressure gauge.

A display structure of a pressure gauge of an air compressor, the air compressor is received in an accommodation box, and a scale portion of the pressure gauge is viewable via a displaying opening of the accommodation box, the pressure gauge includes a cylindrical body which is transparent and is formed in a pen shape, and the pressure gauge includes a colored O-ring configured to indicate a pressure value of the scale portion. The scale portion is not printed on the cylindrical body of the pressure gauge and includes a transparent panel on which the pressure value of the scale portion is marked on an internal face of the transparent panel, and the internal face faces the cylindrical body of the pressure gauge.

A pressure gauge contains: a body and a casing. The body includes a scale disc fixed on a top thereof. The casing is transparent and includes a close segment formed on a first end of the casing, an open segment formed on a second end of the casing, and multiple hooks spaced and arranged on an outer wall of the casing proximate to the opening segment.

A pressure gauge contains: a body and a casing. The body includes a scale disc fixed on a top thereof. The casing is transparent and includes a close segment formed on a first end of the casing, an open segment formed on a second end of the casing, and multiple hooks spaced and arranged on an outer wall of the casing proximate to the opening segment.

A pressure gauge flange assembly for connection to pressure equipment and a pressure gauge. The pressure gauge flange assembly has a flange housing with a flange at a lower portion that connects to pressure equipment such as a BOP. Within the flange housing a chamber is provided that is separated into two chambers by a piston. The piston is moveable to balance pressure in the two chambers. Fluid from the pressure equipment may be dirty. On the other side of the piston, clean fluid is provided so that any dirty hydraulic fluid from the pressure equipment does not impair operation of the pressure gauge.

A pressure gauge includes an introduction member, a connection member, a bourdon tube, a pointer, a dial plate, a detector, and an information communication unit. A battery installed in the information communication unit is disposed between a circuit board and a lid. The information communication unit is inserted in a through hole of the dial plate to be disposed astride between a front surface and a rear surface of the dial plate and the lid is disposed on a side of the information communication unit close to the front surface of the dial plate.