Please give us all a little more information: Temp Control Temp Range? Type of TC or RTD? What type of process(es) need to be controlled? Heat?, Heat/Cool? Method(s)? Communication Bus used by your PLC and/or Plant Monitoring System? If you put this out to all of us, I'm sure you'll get the advice you seek! John "Amazing" Grace, [email protected]
Communication is no problem in today technology. The loops: two main cases are commonly encountered: 1.- The process has lot of inertia (reservoir, furnace...) 2.- The process is in line with the detector. Both will exhibit different reaction curve, because the dominant influence (time constant)is from either the process or the measurement. Whatever is the case, you will need a complete PID loop. Tuning is very successful using Zieggler Nichols method. Despite the suggestion, there are unusual situations where the process has such inertia, ON/OF control copes better. This is particularly true when the process undergoes cycling. Your controller should allow feedforward control. So that the PID will be less busy in the affair !
The Omron E5xN series offers temperature control or the E5xK offers process control. These units can be interfaced via RS232/485 (option) directly to an Omron PLC or other via standard SND & RXD commands. Can multidrop units also on an RS485 network back to a single controller. email ([email protected]) me if you require further info or visit Omrons web site at www.oeiweb.omron.com
