What Is a Pressure Switch?
A pressure switch is a type of sensor that detects pressure from a fluid such as air or liquid. The switch is activated by the absolute value of the pressure, or by the magnitude of the change in pressure relative to an arbitrary pressure value.
There are two types of pressure switch sensors. One is semiconductor piezoresistive diffusion pressure sensors that detect pressure changes based on changes in the amount of current or voltage flowing through a built-in piezoelectric element. The other is capacitance-type pressure sensors that detect pressure changes based on changes in the capacitance of a built-in capacitor with a movable pole caused by external pressure. The capacitance-type pressure sensor has a built-in capacitor with a movable pole.
Uses of Pressure Switches
Pressure switches are used in a variety of applications. They are used to control presses and molding equipment, as well as engine oil in automobiles and brake pressure in trains.
Pressure switches can also be used in harsh environments where they come in contact with corrosive or toxic chemicals. Explosion-proof pressure switches are also available for use where flammable substances are handled. These pressure switches are used in the chemical, oil, and gas industries, where chemicals are handled on a daily basis.
Pressure switches are also used to control the air volume of air conditioner compressors, cooling gases, vacuum cleaner suction, etc., and to control the pressure of pumps and compressors in production equipment.
Principle of Pressure Switches
Pressure switches convert changes in pressure into electrical signals. There are three ways to express pressure changes: first, as positive or negative pressure based on atmospheric pressure; second, as an absolute value of pressure; and third, as a differential pressure, which is a change in pressure relative to an arbitrary pressure.
There are two methods of converting pressure into an electrical signal. The first is the semiconductor piezoresistive diffusion pressure sensor. The second method is the capacitance-type pressure sensor, which contains a capacitor with movable poles. When pressure is applied to the sensor, the capacitance of the capacitor changes due to the deformation of the movable pole. The amount of pressure change can be determined from this change.
Types of Pressure Switches
The type of pressure switch used depends on the environment in which it is installed, the type of fluid with which it comes into contact, and the magnitude of the pressure to be detected. If the fluid is air, a pressure switch for air is used, and if the fluid is liquid, a pressure switch for general-purpose fluids is used. In environments where the fluid comes in contact with flammable substances such as organic solvents or natural gas, an explosion-proof pressure switch should be used.
In other environments where highly corrosive or toxic substances are present, pressure switches with chemical resistance should be used. When using pressure switches in locations where highly toxic substances are present, it is recommended to check not only the inside of the sensor, but also the chemical resistance of each part of the switch.