The present application provides a self-diagnostic gas density relay and a use method thereof, the gas density relay includes a gas density relay body, a gas density detection sensor, at least one diagnostic sensor, and an intelligent control unit; where the diagnostic sensor is configured to acquire deformation quantities of components that generate deformations, and/or positions or displacement quantities of components that generate displacements when the pressure changes, or the temperature changes, or the gas density changes in the gas density relay body; and the intelligent control unit is respectively connected with the gas density detection sensor and the diagnostic sensor, receives data acquired by the gas density detection sensor and/or the diagnostic sensor, and diagnoses a current working state of the gas density relay body. The present application is used for monitoring a gas density of the gas-insulated or arc-extinguished electrical equipment, and at the same time, on-line self-inspection for the gas density relay is completed, so that efficiency is increased, no maintenance is realized, operation and maintenance costs are greatly reduced, and safe operation of a power grid is guaranteed.

A pressure gauge includes a housing, a helical tube, and a compensation member. The housing has an inlet. The helical tube is arranged within the housing and has a closed end and an open end, the open end of the helical tube in fluid communication with the inlet. The compensation member is arranged between the between the open end and the closed end of the helical tube, the compensation member fixed to the helical tube. The compensation member and the helical tube are formed from materials having different coefficients of thermal expansion to limit movement of the closed end of the helical tube due to temperature change of a compressed fluid in fluid communication with the helical tube. Pressure vessel assemblies and methods of displaying pressure in pressure vessels are also described.

A pressure gauge includes a housing, a helical tube, and a compensation member. The housing has an inlet. The helical tube is arranged within the housing and has a closed end and an open end, the open end of the helical tube in fluid communication with the inlet. The compensation member is arranged between the between the open end and the closed end of the helical tube, the compensation member fixed to the helical tube. The compensation member and the helical tube are formed from materials having different coefficients of thermal expansion to limit movement of the closed end of the helical tube due to temperature change of a compressed fluid in fluid communication with the helical tube. Pressure vessel assemblies and methods of displaying pressure in pressure vessels are also described.

An item monitoring system including a bladder having a body with a hollow interior configured to be filled with a fluid is described. The system includes an indicator fluidly connected to the hollow interior of the body of the bladder, the indicator including a movable component configured to visually indicate a fullness of the shelf with one or more items in a non-electrical manner. The connection between the indicator and the bladder defines a closed system. Displacement of the fluid from the bladder into the indicator moves the movable component of the indicator to indicate the fullness of the shelf.

The present application provides a self-diagnostic gas density relay and a use method thereof, the gas density relay includes a gas density relay body, a gas density detection sensor, at least one diagnostic sensor, and an intelligent control unit; where the diagnostic sensor is configured to acquire deformation quantities of components that generate deformations, and/or positions or displacement quantities of components that generate displacements when the pressure changes, or the temperature changes, or the gas density changes in the gas density relay body; and the intelligent control unit is respectively connected with the gas density detection sensor and the diagnostic sensor, receives data acquired by the gas density detection sensor and/or the diagnostic sensor, and diagnoses a current working state of the gas density relay body. The present application is used for monitoring a gas density of the gas-insulated or arc-extinguished electrical equipment, and at the same time, on-line self-inspection for the gas density relay is completed, so that efficiency is increased, no maintenance is realized, operation and maintenance costs are greatly reduced, and safe operation of a power grid is guaranteed.