I have a GE 90-30 CPU 374 PLUS. The program currently has a PID controller that controls a valve. I would like to add a second PID controller to control fans. However I am having a problem implementing the 2nd PID controller. When I upload the program and run it, all the parameters are constantly changing. The P,I and D gains fluctuate, upper/lower clamps, etc are changing. The original controller still functions properly. Moreover, if I remove the old controller (mixing valve) and run it, the new fan controller now runs fine. I ensured that the controllers each have enough reserved memory (40 words). Has anyone had any similar problem?
Sounds like something is being overwritten. Are you sure the new PID addresses are not used elswhere? Have you done an implicit search?
Are you using Proficy ME to program? The 374's are known to be a little flaky, even though they are the highest-end CPU you can get for a 90-30 platform. Are you using PID in ladder, or in a FBD?
turns out i did have something that was overwriting the PID registers