4-20mA – 2 wires

2 wires

2 wire 4-20mA current loop is mainly used for connecting sensors, in a 2 wire current loop the power supply for the sensor is delivered by the loop, therefore, an extra power supply is not necessary.

An output signal in 2-wire technology means:

  • less wiring required
  • better EMC protection, since interferences can be filtered more easily
  • better protection against wiring errors


The sensors can be wired directly into analog input modules on PLC’s or Process Controllers that accept 4 – 20 mA signals. The sensor must be connected to a power source at the positive lead and the common (negative) lead will be connected to the Controller’s Analog Input. The power supply is used to complete the loop through the Controllers Ground.