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How to use analog signals in PLC programming?
Many people struggle with analog signals in PLC programming. The wiring and how to use an analog input or output in your PLC program can be tricky. Most often you will see digital example PLC programs and in my Structured Text Tutorial most of the examples are digital programs.
What does the binary number represent in plc?
The binary number can therefore represent values from -32.768 to 32.767. When the analog input signal enters the PLC it goes through an A/D converter or analog to digital converter. This is the component in the PLC analog input card that transforms the analog signal to digital signals.
What do you need to know about scaling in plc?
When the analog input signal enters the PLC you will often have to scale it in your PLC program. What scaling means is that you convert the raw value from the analog input to some sort of engineering value.
How is the output of a PLC transmitter determined?
Connected to the transmitter is a temperature sensor. The transmitter is then calibrated to a range of e.g. 0-100 degrees. What this means is that when the temperature is 0 degrees the output of the transmitter will be 4 mA, and 20 mA by 100 degrees.
How are sinking and sourcing used in a PLC?
Below are detailed electrical diagrams for sinking and sourcing configurations, showing typical PLC input module and field device circuitry. In order for a PLC I/O circuit to operate, current must enter at one terminal and exit at another. This means at least two terminals are associated with every I/O point.
How does the PLC connect to the common terminal?
So, start at the PLC input terminal, follow through the input sensing circuit, exit at the common terminal, and connect the supply (-) to the common terminal. By adding the switch between the supply (+) and the input, the circuit is completed. Current flows in the direction of the arrow when the switch is closed.
How does a PLC I / O circuit work?
In order for a PLC I/O circuit to operate, current must enter at one terminal and exit at another. This means at least two terminals are associated with every I/O point. In the figure below, the input or output terminal is the main path for the current. One additional terminal must provide the return path to the power supply.