Numerical System in PLC

Numerical System in PLC is numbers or system numbers used by the PLC in performing logic operation.

Numerical Sytem in PLC

This numerical system must be understood, when we will learn about programming of PLC. The following descriptions will explain the numerical system and terms are often used in PLC programming techniques:

1.Decimal Number (Dec)
This numerical system is the number we use in every day. Everyone certainly have understood. In the program PLC is usually used as " setting value" or actual value. For example on the " Timer instruction" on Omron PLC, decimal value is marked with "#". And in Mitsubishi PLC is marked with "K".

2. Binary Number (Bin) 

It is base-2 numerical system which represented with value 0 and 1. This numbers can be grouped with the terms as follows:

1. Bit, the basic of binary numbers with the value of 0 or 1.
2. Nibble, composed of sequential 4 bits. example: b3 to b0 called one nibble.
3. Byte, composed of sequential 8 bits. example : b7 to b0 called one byte.
4. Word, composed of sequential 16 bits. example : b15 to b0 called one word.
5. Double words, composed of sequential 32bits. example: b31 to b0 called double words.

3. Binary Code Decimal (BCD)

BCD is used to express decimal digit with a nibble or 4 bits. 4 decimal digits can be expressed by sequential 16 bits.

4. Hexadecimal(Hex)

It is base-16 numerical system. For the numbers 0 to 9, either in decimal (dec) or hexadecimal (dec) is the same. While the numbers 10 to 15 in decimal would be as follows : 10=A, 11=B, 12=C, 13=D, 14=E, 15=F.
5. Octal
It is base 8 numerical system and uses digit 0 to 7. This numerical system usually used on input output or I/O PLC.