Because what is really going on, is that the PLC works with binary numbers. But that does stop us from working with analog signals. The answer is binary numbers! Representing Analog Signals with Binary NumbersĪs mentioned before a PLC can only work with the two values 0 and 1.
We cannot represent it with boolean values, because they can only have the values 0 and 1. The question is now: how do a PLC deal with all these different values? Let’s say you have an analog signal at 5 volts going into the PLC. If you look at the diagram below, you will see that the analog signal can have any value between 0 and 10 volts. And since analog signals are continuous, this signal will always at any time represent a voltage level. This signal can vary from 0 to 10 volts and have any voltage level in between. But what about analog signals? As Wikipedia writes, analog signals are continuous signals that can vary over time.įor example you can have a 0-10 volt analog signal. They are either 0 or 1 and thereby relatively easy to work with. A PLC can only work with the values 0 and 1. If you’ve read my article about combinatorial logic you will know that a PLC works with boolean values. Analog Signals in the PLCįirst of all, we are going to look at some numbers.
Representing Analog Signals with Binary Numbersīut first, let me start out with some basics about analog signals and how they work in a PLC.So how do you connect that 4-20mA analog transmitter to your PLC and use it in your PLC program? How do you scale an analog signal in Function Block Diagram? This article will give you answers to this and much more. Analog signals are used widely in PLC programs but also often used in a SCADA system.
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I’m writing this article because many of you wanted to learn how to use analog signals in PLC programming. Most often you will see digital example PLC programs and in my Structured Text Tutorial most of the examples are digital programs. The wiring and how to use an analog input or output in your PLC program can be tricky. Many people struggle with analog signals in PLC programming. Do you know how to scale your analog input? Or wire your analog output?
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