Let’s study the working of converter instruction in Siemens PLC programming using different ladder logics and programs.
Converter Instruction in PLC
Block Description
Round to double integer:
It reads the input floating point value and converts it to double integer and round to nearest integer. The result is output by the parameter OUT.
Truncate double integer part:
It reads the input floating point value and converts it to double integer and round to zero mode. The result is output by the parameter OUT.
Ceiling:
It reads the input floating point value and converts it to double integer. The result is the lowest integer which is greater than the floating point number i.e Round to + infinity mode. The result is output by the parameter OUT.
Floor:
It reads the input floating point value and converts it to double integer. The result is the greatest integer component which is greater than the floating point number i.e Round to -infinity mode. The result is output by the parameter OUT.
Ladder Logic
Ladder Description:
Network 1:
If I0.0 is pressed, value in MD0 (99.78) is read as a floating point number and converted to the closest double integer(100). The result of round to integer is stored in MD4(100).
Network 2:
If I0.0 is pressed, value in MD0 (99.78) is read as a floating point number and converted to the double integer. The integer part of the floating point number is the result. The result is stored in MD12 (99).
Network 3:
If I0.0 is pressed, value in MD0 (99.78) is read as a floating point number and converted to the double integer by round function . The result is stored in MD12 (100).
Network 4:
If I0.0 is pressed, value in MD0 (99.78)is read as a floating point number and converted to the double integer by the round to – infinity mode. The result is stored in MD16(99).
Note: For positive numbers, trunc and floor give the same result. But for negative numbers, floor rounds down and trunc rounds up. This is because trunc always rounds toward 0.
Author: Hema Sundaresan
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