EM SD Optical Level Switch

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EM SD Optical Level Switch


Refraction index of plastic and air varies in big range.  Infrared light can be easily reflected totally between plastic and air.  In contrast, infrared light would totally penetrate through plastic while plastic and liquid are taken place.  Optical switch operates by sensing the difference of refraction index between various mediums, which causes different degree of refraction and penetration.

When dry, the transmitted light is reflected by the prism back to the receiver.  When the sensor is wetted in liquid, only part of the transmitted light would be reflected back to the receiver while most is lost into the liquid.  The received light then changes the signal and controls the switching accordingly.

Optical switch is equipped with infrared source and receiver.  They are to detect and verify the status of infrared light reflection and penetration between the mediums in order to trigger the alarm output.

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Product Description


  • M12 or 3/8″G (PF) of connection
  • NPN, PNP Open collector output to energize relay or PLC
  • Over-current and reverse polarity protected
  • LED status indication
  • IP68, PC, Polysulfone or SUS304 
  • Pressure range 10 kg/cm2 for PC, Polysulfone, 40 kg/cm2 for SUS304
  • Low level liquid detect ( 3 mm )