User Guide - Eurotherm Ltda

nanodac RECORDER/CONTROLLER: USER GUIDEAppendix B CONTROL LOOPSNote: See section 4.6 for Loop configuration detailsB.1 INTRODUCTIONWith this recorder, two control loops are available, each loop containing two outputs (Channel 1 and Channel2) which can be individually configured for PID, On/Off or valve position. For temperature control, channel1 is normally configured for heating and channel 2 for cooling.B1.1 EXAMPLE (HEAT ONLY)Controller (simplified)Process under controlSetpoint(SP)Control algorithm(PID, On/Off, VP)ErrorControloutput(OP)PV (Measuredtemperature)ControlloopTemperaturetransducerPowerregulatorHeaterFigure B1.1 Control loop exampleThe measured temperature (process variable, or ‘PV’) is connected to the input of the controller, where it iscompared with the ‘Setpoint’ (SP) (the target temperature). If there is a difference between the PV and theSP, the controller calculates and outputs a heating demand. This output is applied to the process heatingdevice, which in turn causes a change in the PV in a direction intended to result in a zero error.B2 CONTROL LOOP DEFINITIONSB2.1 AUTO/MANUALIn manual mode, if ‘On/Off’ control is configured, the output power may be edited by the user but the onlypower values allowed are: +100% (heat on; cool off) for positive user entries, 0% (heat off; cool off) for zeroentry or -100%. (heat off; cool on) for negative entries.In manual mode, for ‘PID’ control the output may be edited between +100% and (if ‘cool’ is configured),-100%. The actual output value is subject to limiting and output rate limit.In manual mode, for valve position control, the up and down arrow buttons directly control (nudge) the raiseand lower relay outputs respectively. It is also possible to control the valve by sending nudge commandsover a serial link, or by software wiring from a suitable parameter. A single nudge command moves the valveby 1 minimum on time; longer nudge demands produce longer valve movements. See section B2.6.10 formore details.If sensor break occurs while the controller is in automatic the controller outputs the sensor break outputpower. In such a case the user can switch to manual control and edit the output power. On returning toautomatic control, the controller checks again for sensor break.If autotune is enabled while in manual mode, the autotune remains in a reset state such that when the userputs the controller into automatic control the autotune starts.HA030554Issue 7 Nov 12Appendix BPage 299