How do npn sensors work

When a metal part, such as a piece of sheet steel or a stamped metal part, made contact with the whisker wire, the circuit became grounded and the relay pulled in. This was a load-sinking connection. NPN control circuits. With PNP, if a load wire shorts to ground, the short can be found relatively easily because there may be visible damage due to the higher-than-normal current that would flow in the absence of a load impedance.

An unprotected, unfused sensor may also have its output blown. If the PNP sensor has integrated thermal, latching, or pulsing short-circuit protection, the existence of a short circuit condition on the load wire will be apparent at the sensor. In the case of a short to ground in an NPN circuit, there is no abnormal current flow; the load is simply pulled in regardless of the sensor state.

This could prove to be somewhat difficult to detect, because if the sensor associated with the grounded load wire is examined, it will be found to have no fault. In the modern industrial world, NPN is considered more common and popular in the Asia-Pacific region simply because of legacy practice and the desire for backward-compatibility.

Nice website and good explanaition, however I still dont know in which situation should I use each other. They have diferences, but why should I use one instead of the other? What do I gain using one or the other? Which one is best? I think it is explained rather well. Trying to use older rate indicators with newer sensors. Just not happening. Kenneth, thank you for your interest in Balluff sensors.

Your application sounds very interesting, however, I think we have several different technology solutions to solve this application including capacitive and photoelectrics. I would suggest that you contact our technical support group to discuss this.

Please call us at or email technical. The next question to ask is, what direction do you want the current to flow? Additional Details: Types of Discrete Electrical Outputs — The majority of sensors used today use Solid-State outputs, not mechanical relays The drawing below shows 2 wires for sensor power and 2 for the switch.

Share this:. Email Print. Like this: Like Loading Thank you. Even a non-technical person can understand your explanation.

Thank you for that good explanation! It was very helpful for me. Good questions Miguel Guedes and John B. The term solid state refers to the type of components used within the sensor. Solid state electronic components such as transistors are used to switch the output of the sensor upon detection of an object. The difference is a result of the internal circuit design and type of transistors used. Why two types? The selection of a PNP sensor verses an NPN sensor is determined by the nature of the circuit the device is to be used in.

When used in a traditional relay type control circuit, it is normally possible to use either the PNP or the NPN type of sensor as shown below. PNP sensors tend to be more commonly used. Traditional relay type control circuit; Use with a programmable logic controller PLC. When selecting a sensor to be used with a PLC, it is very important that the sensor matches the type of PLC input card to be used.