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3-Wire Sensors

3-Wire Sensors for Direct-Current Voltage Operation

3-wire sensors are sourcing, type "PNP", or sinking, type "NPN", with separate connections for the power supply and for the output. These sensors are protected against overload, short circuit, and reverse polarity. The residual current is negligible. For sensor type PNP, the load is connected between the output and ground potential (L-). For sensor type NPN, the load is connected between the output and L+.


Depending on the type of output-stage transistor used, sinking output stages are often referred to as NPN output stages. Sourcing end stages are referred to as PNP output stages.

Sensor Connection—Example 

Example of a 3-wire sensor in direct-current voltage operation

3-Wire Sensor Versions

These sensors are usually marked with the following in the third block of the Pepperl+Fuchs order designation:


Sensors of type –E are available in the following switching element functions:

  • NPN, normally-open (E0, formerly E)
  • NPN, normally-closed (E1)
  • PNP, normally-open (E2)


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