What are Reed switch/sensors?

Reed switch is also called an inductive-magnetic sensor, so it is grouped in special inductive sensors. Reed switch is printed in a bakelite box.

If the switch enters a magnetic field, the contact feathers become closed, and the sensor provides electrical signals.
The reed switch proximity sensor works on a magnetic basis, so the symbol also contains proximity symbols and magnetic symbols:

Working of Reed switch:

The proximity reed switch sensor is a magnetically actuated sensor, in principle this sensor is designed for cylinders made with sensing capability (ie permanent magnets on the cylinder piston area), but some of them can also be used in other areas where proximity to the magnetic field is a requirement for producing an electrical control signal.

If the pneumatic cylinder design incorporates a permanent magnet on the piston, the reed switch proximity sensor attached to the outer side of the cylindrical tube can be used to signal when the cylinder piston rod passes through it. If the magnet piston enters the response area of the sensor, the magnetic field causes the contact hair to reed switch inside the sensor to close, equipped with the LED indicator light and activating the output signal. If the magnet moves away from the response area, reed switch opens again; The LED and the output signal are back off.

Usually, the proximity sensor uses 3 cables, which are 2 cables to be connected to the supply voltage, and 1 cable for the output signal. Besides that, there is also a reed switch proximate sensor with 2 cables.

Electrical characteristics for sensors:

  • Direct voltage (DC) sensor – 24V DC
  • Voltage ranges from – 10 V … 30 V, 10 V … 60 V, 5 V … 60 V
  • Supply of alternating voltage (AC) -115 V … 230 V AC
  • Voltage around – 98 V … 253 V AC
  • Frequency of 48 Hz to 62 Hz
  • AC / DC voltage sensor
  • 10 V Voltage Range … 30 V DC, 24 V … 240 VAC.

Advantages of Reed switch:

  • Compact and lightweight
  • Relatively stable characteristics are ensured from low to high temperature
  • High reliability due to the long lifetime
  • High-speed operation
  • Reed switch finds extensive application in switching and sensing

Disadvantages of Reed switch:

  • EM interference
  • Inductive load
  • Capacitive load
  • Mounting, solder bending cutting
  • Shock and vibration


Instrumentation Engineer

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