Grey Code
Grey Code is used because only one bit of data will change at a time. The following chart shows the conversion of Grey Code to Binary.

Number	Binary Code	Grey Code	Number	Binary Code	Grey Code
0	0000	0000	8	1000	1100
1	0001	0001	9	1001	1101
2	0010	0011	10	1010	1111
3	0011	0010	11	1011	1110
4	0100	0110	12	1100	1010
5	0101	0111	13	1101	1011
6	0110	0101	14	1110	1001
7	0111	0100	15	1111	1000

It is important for absolute encoders because if the power is interrupted the encoder will know where it is within the one bit.



Example:
Power is interrupted when the encoder is between 7 and 8. If we are looking at Binary Code all of the bits would be affected and we would not be sure as to what number we are looking at for the encoder. Therefore we have lost our position. In Grey Code only one bit changes so we will still be able to tell if we were on 7 or 8 if the power was interrupted.

The following sample PLC program will convert 4-bit grey code into binary code.
This code was written in an Automation Direct PLC software called Do-more Designer.

Do-more Designer Software
How to use videos for Do-more Designer Software

Contact me for the above program. I will be happy to email it to you.
Thank you,
Garry



If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

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