Magnetic safety sensors

Safety magnetic sensors

Safety magnetic sensors (reed switches) are non-contact switches that respond to changes in the magnetic field using a coded magnet . When the magnet is close enough to the sensor (they detect the presence of a permanent magnet within 10mm), current begins to flow through the circuit and a signal is generated that allows the machine to start. This reaction is a change in the operating state of the sensor from open to closed as a result of close contact with an object emitting a magnetic field.

Principle of operation and construction

Magnetic sensors work by changing the coupling between the electric and magnetic circuits or by the influence of the magnetic field on the material parameters of the sensor. They convert a signal proportional to the induction or strength of the magnetic field in the air into an electrical signal: voltage, change in resistance, frequency.

For its construction, reed switches are very often used, which have contacts closed in a hermetic glass housing filled with an inert gas. Thanks to the intelligent arrangement of the reed contacts, a high degree of protection against manipulation is achieved. This reduces the risk of bypassing the safeguards of the machines and components they supervise.

As long as the reed switch remains in the magnetic field, the circuit is closed (NC - normally closed). However, when the reed switch is outside the magnetic field range, the circuit opens (NO - normally open).

Reed magnetic sensors react to the appearance of a magnetic field within their range, or they use a system of magnet and reed switch, in which operation occurs when the latter leaves the magnetic field.

Safety magnetic sensors - applications

Safety magnetic sensors are used in mechanical engineering as well as in industrial automation. They are commonly used in production lines and machining machines wherever precise machine control is required.

Magnetic sensors due to their compact design, no mechanical elements , are used in many industries and fields, often also in those where working conditions are very difficult, for example due to very high temperature , high pressure, dust and water.

They are used for detecting progressive or rotating objects, detecting objects in difficult environments as well as detecting objects behind walls.

They are used wherever permanent control of the state of safety guards is required. When the cover is closed, the magnet is close to the sensor. If opened, the machine is immediately restored to a safe condition. Magnetic sensors work well in places where high hygiene requirements are imposed or where difficult working conditions preclude the use of electromechanical switches.

Safety magnetic sensors do not have mechanical components, so there is no wear on the components. The use of the appropriate safety relay module and enabling the implementation of the forced opening function of normally closed contacts makes it possible to achieve even 4 safety category .

Non-contact magnetic reed safety switches are perfect for monitoring safety doors - especially in places where dirt or dust is to be expected.

Advantages of using magnetic safety sensors

Magnetic sensors are used in almost every industry. They have a number of advantages, including small physical size, relatively high sensitivity and resistance to the influence of external factors. Due to the non-contact principle of operation, they are insensitive to mechanical play. An additional advantage is the lack of mechanical parts in magnetic sensors, which results in no wear of components . Diversified housing allows a wide range of applications.