User Guide - Eurotherm Ltda

nanodac RECORDER/CONTROLLER: USER GUIDEB2.4.2 Loop ResponseIgnoring loop oscillation, there are three categories of loop performance viz Under damped, Criticallydamped and Over damped:UNDER DAMPEDIn this situation the parameters are set to prevent oscillation but lead to an overshoot of the Process Value(PV) followed by decaying oscillation until the PV finally settles at the Setpoint. This type of response cangive a minimum time to Setpoint but overshoot may cause problems in certain situations and the loop maybe sensitive to sudden changes in PV, resulting in further decaying oscillations before settling once again.CRITICALLY DAMPEDThis represents an ideal situation where noticeable overshoot to small step changes does not occur and theprocess responds to changes in a controlled, non oscillatory manner.OVER DAMPEDIn this situation the loop responds in a controlled but sluggish manner which results in a non-ideal and unnecessarilyslow loop performance.B2.4.3 Initial SettingsIn addition to the tuning parameters listed above, there are a number of other parameters which can affectloop response. These parameters must be correctly configured before tuning is initiated. Parameters include,but are not limited to:-SETPOINTBefore tuning, the loop conditions should be set as closely as practicable to the actual conditions which willbe met in normal operation. For example, in a furnace or oven application a representative load should beincluded, an extruder should be running, etc.OUTPUT HIGH, OUTPUT LOWThese Output menu heat and cool limits define the overall maximum and minimum power which may bedelivered to the process by the control loop. For a heat only controller the default values are 0 and 100%.For a heat/cool controller the defaults are -100 and 100%. Although most processes are designed to workbetween these limits there may be instances where it is desirable to limit the power delivered to the process.REM. OUTPUT LOW, REM. OUTPUT HIGHIf these Remote Output Limits parameters (Output menu) are used, they are effective only if they lie withinthe Heat/Cool Limits above.CH2 DEADBANDHeat/Cool Dead band If a second (cool) channel is configured, a parameter ‘Ch2 Deadband’ is also availablein the Output menu which sets the distance between the heat and cool proportional bands. The defaultvalue is 0% which means that heating will cease to be available at the same time as cooling becomes available.The dead band may be set to ensure that there is no possibility of the heat and cool channels operatingtogether, particularly when cycling output stages are installed.MINIMUM ON TIMEIf either or both of the output channels is fitted with a relay or logic output, the parameter ‘Min On Time’ appearsin the output menu. This is the cycling time for a time proportioning output and should be set correctlybefore tuning is started.FILTERThe ‘Filter’ parameter is found in the Channel ‘Main’ menu (section 4.4). It is used to remove noise from slowlychanging signals so that the underlying trend can be seen more clearly.Appendix BPage 306HA030554Issue 7 Nov 12