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What is a Magnetic Proximity Sensor?Its working,Advantages ,Disadvantages & Applications

The technique of detecting the presence or absence of an object utilizing a critical distance is known as proximity sensing. In this blog, we will discuss the Magnetic Proximity Sensor’s operating concept, as well as its features and uses. Magnetic proximity sensors detect magnetic objects without requiring any interaction (e.g. permanent magnets). They detect a magnetic object’s presence.The blog covers the basics of magnetic proximity sensors, its working, applications, and advantages and disadvantages.

 Magnetic proximity sensor

Magnetic proximity sensors use for non-contact position detection beyond the normal limits of inductive sensors. In conjunction with a separate “damping” magnet, magnetic sensors offer very long sensing ranges from a small package size and can detect magnets through walls of non-ferrous metal, stainless steel, aluminum, plastic or wood.

Magnetic proximity sensors are non-contact proximity devices that are used to detect magnetic objects (e.g. permanent magnets).  They detect the presence of a magnetic target, also known as the target. When the target approaches the sensor’s detection range, the switching process is triggered by its magnetic field. The device could function via inductive, variable reluctance, magneto resistive, or hall effect operating principles, or it could be a reed switch.

The sensor damped from the front or from the side, depending on the orientation of the magnetic field. The magnetic sensor is used in conjunction with cleaning devices that travel through the inside of pipes in the food sector.

Output of Magnetic proximity sensor

The magnetic field sensor output can be either linear, in which case the output voltage is proportional to the magnetic field strength impinging on the detector, or binary, in which case the output is in one state when the measured magnetic field strength exceeds a threshold, and in the other state when the measured magnetic field strength falls below the threshold. Because binary proximity sensors have no moving parts to wear out or jam, they are more reliable than mechanical proximity switches.

Features of Magnetic proximity sensor

  • Detection through plastic, wood, and any non-magnetisable metals
  • Small housings with very long sensing ranges up to 70 mm
  • Cylinder and rectangular designs satisfy space-dependent applications
  • High mechanical stability in case of shock or vibration
  • Flush or non-flush installation in non-magnetisable metals

Working Principle of Magnetic Proximity Sensor

Reed switches, GMR inductive, variable reluctance, magneto resistive, and hall effect sensors are some of the operating principles employed.

  • Variable reluctance

A permanent magnet and a pick-up coil make up proximity sensors. A VR sensor, which functions as a simple proximity sensor, can be used to determine the position of a mechanical connection in industrial machinery.

In an automotive engine, a crankshaft position sensor sends the angular position of the crankshaft to the engine control unit. Engine speed can then be calculated by the engine control unit (angular velocity).

The vibrations of the metallic “strings” are detected by a pickup in an electric guitar or other musical instrument

  • Magneto-resistive 
Magneto resistive sensor

The magneto-resistive effect, or the impact of a ferromagnetic material’s resistivity in the presence of a magnetic field, is measured by proximity sensors.

The tendency of a material to change the value of its electrical resistance in response to an externally applied magnetic field is known as magneto-resistance.

  • Reed Switches

Reed switches are switches that are activated by magnets. Two ferromagnetic reeds (contact blades) are commonly used, which are sealed in a glass capsule. Two low-reluctance ferro-magnetic reeds are contained in glass bulbs filled with inert gas.

reed switch

A magnetic field from an electromagnet or a permanent magnet will cause the reeds to attract each other to establish  an electrical circuit. When utilized as a proximity switch for a security alarm, a reed switch can be used to detect the opening of a door.

  • Giant Magneto-Resistive Effect

GMR (Giant Magneto-Resistive Effect) technology is used in magnetic sensors. The measuring cell is made up of resistors with ferromagnetic and non-magnetic layers that are exceedingly fine.

GMR

When a magnetic field is present, two of these GMR resistors make a typical Wheatstone bridge circuit, which produces a large signal proportionate to the magnetic field. A comparator switches an output signal based on a threshold value.

The main application of GMR is magnetic field sensors, which use to read data in hard disk drives, biosensors, microelectromechanical systems (MEMS) and other devices. GMR multilayer structures are also used as single-bit storage cells in magneto-resistive random-access memory (MRAM).

  • Hall effect sensor

Hall effect sensor is a device that uses to measure the magnitude of a magnetic field. Its output voltage is proportional to the strength of the magnetic field passing through it.

Hall effect sensor

Hall effect sensors used for proximity sensing, positioning, speed detection, and current sensing applications. Frequently, a Hall sensor combines with threshold detection so that it acts as a switch. 

Advantages of Magnetic proximity sensor

  • Contacts are well protected against dust, oxidization and corrosion due to the hermetic glass bulb and inert gas; contacts are activated by means of a magnetic field rather than mechanical parts
  • Special surface treatment of contacts assures long contact life
  • Maintenance free
  • Easy operation
  • Reduced size

Disadvantages

  • They are affected by temperature and humidity.
  • Difficulties in designing.
  • The operating range may be limited.
  • It detects only the metallic target.
  • They can be easily set off and cause a problem.

Applications of Magnetic proximity  Sensor

Magnetic sensors are utilized for contactless current detection, linear and angular position sensing, and rotation sensing in a variety of industrial applications.

  • Magnetic Sensors for PDU

The power distribution unit (PDU) is an important component of data center infrastructure. PDU equipment is used to provide AC or DC power to servers. The PDU usually includes power filtration and adaptive load balancing, as well as remote monitoring.

  • Robotics and Factory Automation

Linear and angular position sensing are required in factory automation to carry out complex motor actions with great precision, repeatability, and accuracy. Magnetic sensors are also employed for linear and angular sensing, safety switches, and proximity detection as a result of the requirement for faster, more efficient production processes.

  • White Goods

New regulatory requirements for energy and water conservation in appliances can accomplish through additional intelligent sensing.  Open/close door detection, fluid level detection, and contactless current sensing are all possible with Crocus magnetic sensors.. 

  • Used in Green Energy

Magnetic sensors allow contact less current detection, angular position sensing, and switches in alternative energy applications such as wind and solar. Contact less current sensors give solutions for power converters and solar combiner boxes, while angular position sensing enables for optimal wind power generation. In high-voltage conditions, switches can also help with safety applications.

Hope this blog helps you to understand basics of magnetic proximity sensors, its working, applications, and advantages and disadvantages.We ,MATHA ELECTRONICS will come back with more informative blogs.

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