If dual type outputs are provided, it will be via two separate, dedicated output wires. The DC powered open-collector sensor may provide either NPN/Sinking type output or open collector PNP/Sourcing type output, or the DC powered sensor may provide dual type outputs (open-collector NPN/Sinking and open-collector PNP/Sourcing). The two DC output “configurations” from a sensor are: NPN/Sinking or PNP/Sourcing) is unknown, then generally it is safe to try an NPN/Sinking sensor type output, and if the PLC or machine does not recognize it, disconnect it, and try the PNP/Sourcing sensor type output, or vice-versa. Note that if what “type” of DC input the PLC or machine needs (i.e.
PNP/Sourcing outputs attempt to take their output to near positive (+) of the supply voltage when the sensor turns ON its output. NPN/Sinking type outputs attempt to take their output to equipment ground or power supply common (near zero volts) when the sensor turns ON its output. It would be prudent to also ask if the existing sensor has a push-pull output configuration? If so, then likely the PLC or machine is designed to accept only sensors with a push-pull output configuration. Since the issues regarding the AC powered sensor and its compatibility with the PLC or machine are relatively straight forward, only DC inputs are discussed here since they are the most popular, and often the most misunderstood.įor PLC’s or machines that require a DC input (DC output from the respective sensor) the typical single question that is often asked is: “Does the PLC or machine need an NPN/Sinking or PNP/Sourcing “type” output from the sensor?” Although the answer to this question is usually sufficient to select the right sensor, it assumes that the output “configuration” of the sensor is compatible with the input “configuration” needs of the PLC or machine. PLC’s or machines will typically require either a form of AC input from an AC powered sensor, or a “type” of DC input and a DC input “configuration” from a DC powered sensor. The main difference between these two types of transistors is that the holes are more important carriers for PNP transistors, while electrons are more important carriers for NPN transistors.In factory automation, sensors not only need to be specified appropriately for the sensing task, but also need to consider what “type” of output and what output “configuration” is required by the PLC or machine to be compatible with it. PNP transistor, the emitter is more positive with respect to the base and also a collector. PNP transistor uses a small base current and a negative base voltage to control a much larger emitter-collector current. In PNP transistor one n-type material is placed between two p-type materials is known as Positive-Negative-Positive type transistor. PNP transistors also are three-terminal, a three-layer device that opposite to NPN transistor where a positive DC voltage is applied to the emitter. In NPN transistor, the direction of movement of an electron is from the emitter to collector region due to which current constitutes in the transistor. It amplifies the weak signals to enter into the base and produces strong amplify signals at the collector end. In NPN transistor one p-type material is placed between two n-types materials is known as Negative-Positive-Negative type transistor. NPN transistors are three-terminal, a three-layer device that can function as either amplifiers or electronic switches.
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