1766-RM001A-EN-P MicroLogix 1400 Programmable Controllers ...

360 Process Control Instruction4. Watch the PV. When the PV starts to change, stop your stopwatch.Record this value. It is the deadtime.5. Multiply the deadtime by 4. This value approximates the naturalperiod. For example, if deadtime = 3 seconds,then 4 x 3 = 12 seconds (≅ natural period)6. Divide the value obtained in step 5 by 10. Use this value as the loopupdated time. For example, if:natural period = 12 seconds, then 12/10 = 1.2 seconds.Therefore, the value 120 would be entered as the loop update time.(120 x 10 ms = 1.2 seconds)7. Enter the following values: the initial setpoint SP value, a reset T i of0, a rate T d of 0, a gain K c of 1, and the loop update timedetermined in step 17.Set the PID mode to STI or Timed, per your ladder diagram. If STI isselected, ensure that the loop update time equals the STI timeinterval.Enter the optional settings that apply (output limiting, output alarm,MaxS - MinS scaling, feed forward).8. Return to page 357 and complete the tuning procedure starting withstep 4.Publication 1766-RM001A-EN-P - October 2008