PLCprogrammer
2020-04-30T19:58:54Z
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?
Guest
2020-04-30T20:00:16Z
Sounds like something is being overwritten. Are you sure the new PID addresses are not used elswhere? Have you done an implicit search?
Zackbo
2020-04-30T20:01:25Z
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?
PLCprogrammer
2020-04-30T20:07:44Z
turns out i did have something that was overwriting the PID registers