User Guide - Eurotherm Ltda

nanodac RECORDER/CONTROLLER: USER GUIDE.Control type PB Ti TdProportional only2 × PB′OffOffP + I2.2 × PB′0.8 × TOffP + I + D1.7 × PB′0.5 × T0.12 × TTable B2.4.7 Calculate parameter valuesSetpointTemperatureR2G correctR2G too largeR2G too smallTimeFigure B2.4.6a Relative Cool GainCUTBACK VALUESThe PID terms calculated from Table 2.4.7, above, should be entered before the cutback values are set.The above procedure sets up the parameters for optimum steady state control. If unacceptable levels ofovershoot or undershoot occur during start-up, or for large step changes in PV, then the cutback parametersshould be set manually, as follows:1. Initially set the cutback values to one proportional bandwidth converted into display units. This can becalculated by taking the value in percent that has been installed into the parameter ‘PB’ and entering itinto the following formula:PB/100 × Span of controller = Cutback High and Cutback LowFor example, if PB = 10% and the span of the controller is 0 to 1200°C, thenCutback High = Cutback Low = 10/100 × 1200 = 120HA030554Issue 7 Nov 12Appendix BPage 315