Pressure relays actually belong to the category of pressure switches, and their output is a contact signal. However, they are commonly used in hydraulic systems and are commonly referred to as pressure relays in the industry (although there may not be conventional concepts of relays or multiple contacts, they may only be a single pair of contacts, such as micro switches). The output contact action pressure value can be adjusted. Pressure relays are generally stronger in nature.

A pressure switch is a device that can output contact signals or high/low potential signals when the set pressure (pressure) value is higher or lower. Its main components are pressure sensing elements and output devices, which can be passive contacts (contacts) or electronic circuit components that can output contacts or high and low potential signals (requiring a working power supply). The medium can be gas or liquid. Its contacts usually only have one pair (normally open or normally closed), but there are also options that can provide two pairs. Pressure switches that output high and low potential signals are available in both 4-wire and 3-wire systems.

Pressure sensors are actually a general term, broadly speaking, any device that can convert pressure signals into other signals (such as current, displacement, capacitance, etc.). But generally refers to pressure transmitters, which convert pressure signals into current signals (such as 4-20mA) or other communication signals