Many shock-resistant pressure gauges will have a sticker (sometimes with a pair of scissors) on the outer casing, which generally means that after installation, the oil plug must be cut or a hole must be poked. The oil plug is originally to prevent the damping oil in the shock-resistant pressure gauge from leaking out. Why do we need to open a hole?
Because ordinary pressure gauges measure relative pressure, the pressure inside and outside the pressure gauge needs to be equal. If it is completely sealed, as the pressure gauge is used, there will be a pressure difference between the pressure inside the gauge and the atmospheric pressure outside. This pressure difference will affect the accuracy of the pressure gauge and may even cause the oil plug to pop out.
