A pressure gauge of which the presence or absence of a measurement error can be easily checked is provided. A pressure gauge includes: a piston; a first conversion mechanism converting a linear motion of the piston against an elastic force of a spring into a rotating motion about a first rotation shaft, the linear motion being caused by the pressure transmitted from a target to be measured; an index that is fixed to one end side of the first rotation shaft; a dial; momentum detecting means for detecting momentum indicating an amount of movement of the piston; and a pressure sensor measuring a pressure value or the pressure acting on the internal space of the cylinder. Determining means determines whether a difference between a first measurement value and a second measurement value exceeds a predetermined value, the first measurement, value being estimated from the momentum detected toy the momentum detecting means, the second measurement value being measured by the pressure sensor. Notifying means notifies a user if the difference between the first measurement value and the second measurement value exceeds the predetermined value.

A pressure indicator with a pressure-relief function is disclosed, which can release excessive pressure to the environment. The pressure indicator includes a transparent tube defining therein a first bore and a second bore, and a slider which can be forced by the medium supplied from an external pressure source to move along the first and second bores of the transparent tube. In particular, the first bore has a diameter greater than the second bore, and a tapered annular surface is provided between the first bore and the second bore of the transparent tube. When the pressure of the medium exceeds a predetermined pressure, the slider can be forced by the medium to reach the tapered annular surface, at which excessive medium can be released into the environment via an annular gap between the slider and the tapered annular surface.

A pen-type pressure indicator, which can be detachably connected to an air compressor for measuring the pressure of compressed air produced in the air compressor, includes a transparent tube and a slider. The slider can be moved along a first bore and a second bore of the transparent tube. The motion of the slider in the transparent tube is similar to the motion of a piston in a cylinder. The transparent tube is provided with a tapered annular surface, between the first bore and the second bore. In addition to measuring the pressure of the compressed air delivered to an object, when the pressure of the compressed air exceeds a predetermined pressure, excessive air can be released into the environment, without requiring the air compressor to be installed with a safety valve, so that the object can be protected from damages due to overpressure.

A pressure indicator, which can be detachably connected to an air compressor for measuring the pressure of compressed air produced in the air compressor, includes a tube and a slider. The slider can be moved along a first bore and a second bore of the tube. The motion of the slider in the tube is similar to the motion of a piston body in a cylinder. The tube is provided with a tapered annular surface, between the first bore and the second bore, and defines an elongated opening. In addition, when the pressure of the compressed air exceeds a predetermined pressure, excessive air can be released into the ambient environment, without using a mechanical safety valve, so that an object can be prevented from over-inflation.

A ball mount for measuring tongue weight of a trailer is disclosed. The ball mount can comprise a ball portion for interfacing with a ball configured to couple with a tongue of a trailer, a hitch portion for interfacing with a hitch receiver associated with a vehicle, and a load measurement device associated with the hitch portion. The hitch portion can be configured to pivot relative to the hitch receiver about a fulcrum in response to a downward force on the ball, with the hitch receiver resisting rotation of the hitch portion about the fulcrum thereby inducing a load on the hitch portion. The load measurement device can be configured to determine a magnitude of the downward force on the ball based on the load on the hitch portion.

A height adjustable hitch receiver is disclosed and described.

A pressure sensor includes a housing with an interior enclosing a plunger unit and a measuring element. The plunger unit includes a distal plunger end separated along a longitudinal axis from a proximal plunger end and further away from the measuring element than the proximal plunger end and protruding from the housing. The proximal plunger end transmits a pressure of a medium prevailing outside the housing to the measuring element. A sleeve is fastened to the housing spaced apart from the distal plunger end by a gap. A sealing element seals the gap to prevent the medium from entering the housing interior.