NPN

What is NPN

NPN is mentioned in many product descriptions. The products include sensors, distribution systems and other components of industrial networks which transmit and process signals from sensors. The abbreviation describes a type of output for sensor signals. In the area of automation technology the term NPN signal is used as well. The output signal of a sensor depends on its set up inside. The core of the sensor is a transistor which depending on physical conditions like pressure, temperature, level, and other values activates the output.

In general there are two types of output signals: PNP and NPN. The order of the letters equals the order of p endowed and n endowed layers in the transistor. Foreign atoms which change electric conductivity were put into an endowed layer made from a basic material. PNP triggering or NPN triggering sensors are other terms which are also used in this area. In contrast to a PNP sensor the load of an NPN sensor is in between the trigger output and the point of reference V+. The minus pole of the supply voltage is activated by the sensor.

PNP sensors are the European standard for automation. NPN sensors are mainly used for the control of machines and plants in Asia.

NPN-Input

The signal of a sensor is processed by higher level network components such as an adapter, a distributor or a control unit (SPS). These components have to be equipped with a suited input (NPN input) which can process the NPN Signal.

Many network components are fitted with the required input. Distributors are available with an NPN input for installation in field (IP67 and other standards) and also with an NPN output to connect three wire sensors. Additionally distribution systems to connect sensors with a PNP signal are available. Even distribution systems with an M8 and M12 plug for NPN signals 24 VDC are available. Digital output modules may have outputs of this type.

Before connecting to a control unit (SPS) it has to be checked whether the SPS has the required inputs for NPN signals.

Digital Input NPN

A digital input NPN allows the connection of a sensor which has an NPN output. Transmission safety is of utmost importance for the correct transmission of signals of a sensor. If a digital signal is preferred due to safety reasons the higher level network component has to have a digital input NPN. If necessary a digital input PNP can be used to transfer a PNP signal.