GE Fanuc adding decimal values to constant problem

[treefort]

Hi,

There is a compare block being used 1100 times to compare variables to a constant value -999. The problem is that the GE is changing the -999 to -999.000128 and the compare block is not working. This used to work. We can't get the turbine going because of this.

Anyone have any ideas?

Much appreciated,

Edit: We've tried the compare logic with a test bench PLC and brand new program. Once downloaded, -999 changes to -999.000128

 

[rdrast]

Don't use absolute compares with floating point values, ever.
Use only relative compares (Greater than, Greater than or equal to, Less than, Less than or equal to).

Normally a simple whole number like that can be represented properly in most floating point formats, but don't count on it. Even with the IEEE standards, there are lots of places for slight differences, and platform specific optimizations.

 

[treefort]

Alright, thanks for the tip.

Just heard from a coworker that installing an older version of Proficy fixed the problem. All good now.