What Is an Air Cylinder Sensor? How Does the Air Cylinder Sensor Work?

Definition of Cylinder Sensors

Cylinder sensor refers to the magnetic induction switch for cylinders (there must be a magnetic ring installed on the cylinder piston ring). The installation positions and quantities of magnetic induction switches are determined based on the requirements for controlling the cylinder situation and detecting signals. Normally, magnetic induction switches are installed at both ends of the cylinder stroke. In a cylinder, three magnetic switches are installed to obtain detection signals when it reaches the middle position of the stroke. At this time, the cylinder can stop moving, or the air cylinder reed switch to slow speed, or immediately switch to fast speed, or transmit the detection signal to other executing mechanisms for other actions, or other signalling needs, etc. It depends on the control requirements. The action does not necessarily need to be performed on this cylinder alone. The setting of magnetic switches can be either one (only need to obtain one detection signal) or multiple (require more position detection signals).

Working Principle of Cylinder Sensors

The cylinder sensor mainly includes magnetic sensors, position sensors, etc. The magnetic sensor can be further divided into mechanical and electronic types. A switch of the magnetic induction sensor is a normally open point. There are magnetic rings on the piston inside the cylinder. When the piston moves to the switch position, the magnetism causes the switch to close.

Wiring Methods of Cylinder Sensors

The switch of the magnetic sensors for cylinders is used to detect the position of the cylinder piston, that is, to detect the movement stroke of the piston. It can be divided into two types: contact type (contact magnetostrictive tube type) and non-contact type (non-contact transistor type). The contact magnetostrictive tube type consists of two magnetostrictive tubes as mechanical contacts, which can be used for both AC and DC power supplies.

When the magnetic ring that moves with the cylinder approaches the inductive switch, the two magnetostrictive plates of the inductive switch are magnetized, causing the contact to close and generate an electrical signal. When the magnetic ring leaves the magnetic switch, the plates lose magnetism and the contact opens, resulting in the disappearance of the electrical signal. In this way, the position of the cylinder piston can be detected to control the corresponding electromagnetic valve action. The non-contact transistor type can be used for DC power supply and is mostly a three-wire type. NPN and PNP should pay attention to the wiring differences when used in relay circuits. When selecting in conjunction with PLC, attention should be paid to the correct selection.

The non-contact inductive switch fundamentally differs in structure and principle from the contact inductive switch. It emits control signals by controlling the internal transistors. When the cylinder sensor magnetic ring approaches the inductive switch, the transistor conducts and generates an electrical signal. When the magnetic ring leaves the magnetic switch, the transistor is turned off and the electrical signal disappears.