Back to the Basics: How Do I Wire a DC 2-wire Sensor?

In one of my previous post we covered “How do I wire my 3-wire sensors“. This topic has had a lot of interest so I thought to myself, this would be a great opportunity to add to that subject and talk about DC 2-wire sensors. Typically in factory automation applications 2 or 3 wire sensors are implemented within the process, and as you know from my prior post a 3 wire sensor has the following 3 wires; a power wire, a ground wire and a switch wire.

A 2-wire sensor of course only has 2 wires including a power wire and ground wire with connection options of Polarized and Non-Polarized. A Polarized option requires the power wire to be connected to the positive (+) side and the ground wire to be connected to the negative side (-) of the power supply. The Non-Polarized versions can be wired just as a Polarized sensor however they also have the ability to be wired with the ground wire (-) to the positive side and the power wire (+) to the negative side of the power supply making this a more versatile option as the sensor can be wired with the wires in a non – specific location within the power supply and controls.

In the wiring diagrams below you will notice the different call outs for the Polarized vs. Non-Polarized offerings.

PolarizedDiagramsnon-polarized diagramsNote: (-) Indication of Non-Polarized wiring.

While 3-wire sensors are a more common option as they offer very low leakage current, 2 wire offerings do have their advantages per application. They can be wired in a sinking (NPN) or sourcing (PNP) configuration depending on the selected load location. Also keep in mind they only have 2 wires simplifying connection processes.

For more information on DC 2- Wire sensors click here.

Shawn Day has experience and knowledge of the industrial automation industry with Balluff. With his product and industry knowledge, he is sharing his passion for automation with Automation Insights.

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