PLC programming the scaling and move instruction
Now and then you may receive some type of analog signal from a device connected to your plc. Usually this signal can come in some type of range in voltage or some type of range in ampere. You may need a way to scale this into a numeric value which can be used in your plc program. For this we use something called the SCP instruction which allow a few inputs and delivers an output which is scaled.
When using scp you would want to provide it the source value, min value and max value. Then the next thing which will be provided is the min scale value and max scale value. So lets for instance say you receive an analog signal between 1 and 10 volts. You could set your min value to 1 and max value to 10. If you had to set your min scale value to 0 and max scale value to 100 then your input value will be put on that scale. For example an incoming signal of 5 volts could be represented as a 50 in your plc program after it being scaled.
These ranged analog signals can be useful when a device outputs certain ranges to your plc to give you different readings. You can then scale them up or down to the ranges which your plc program can handle. Usually light and temperature sensors make use of this sort of analog signal. Other types of protocols such as modbus has more control however analog signalling can also be used in your plc programming.
PLC programming the mov operation
Let’s quickly talk about the MOV instruction. This takes a memory address as a source and memory address as a target. With the mov operator we move one memory address’s contents to another memory address. See the below example of a ladder program which has a move instruction set up.
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