Sinking versus sourcing
In automation engineering, the concepts of sinking and sourcing are very important. Sinking and sourcing is, in lay terms, the direction of the current flow. For example, consider Figure 2.1:
Figure 2.1 – Sinking and sourcing
In Figure 2.1, the arrow that represents the current is going from Device 1 to Device 2. This means that Device 1 is the sourcing device, and Device 2 is the sinking device. If the arrow is reversed, then Device 2 would be sourcing, and Device 1 would be sinking. In other words, this concept boils down to the direction of the current flow.
NPN versus PNP
Another way to think of sinking and sourcing is to consider an NPN or PNP device. For many who have studied electronics in the past, PNP and NPN may seem very familiar because they are the two basic types of transistors. The easiest way to conceptualize NPN and PNP devices is as follows:
- PNP: A PNP device is a sourcing device. This means...
