Marathon Computer AACC 2000 manual One-shot Tuning, How to tune

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Marathon Monitors Inc.

AUTOMATIC TUNING

Two automatic tuning methods are provided in the AACC 2000:

∙A one-shot tuner, which automatically sets up the initial values of the parameters listed in Table 4-1 on the previous page.

∙Adaptive tuning, which continuously monitors the error from setpoint and modifies the PID values, if necessary.

One-shot Tuning

The ‘one-shot’ tuner works by switching the output on and off to induce an oscillation in the measured value. From the amplitude and period of the oscillation, it calculates the tuning parameter values.

If the process cannot tolerate full heating or cooling being applied during tuning, then the level of heating or cooling can be restricted by setting the heating and cooling power limits in the ‘oP’ list. However, the measured value must oscillate to some degree for the tuner to be able to calculate values.

A One-shot Tune can be performed at any time, but normally it is performed only once during the initial commissioning of the process. However, if the process under control subsequently becomes unstable (because its characteristics have changed), you can re- tune again for the new conditions.

It is best to start tuning with the process at ambient process variable. This allows the tuner to calculate more accurately the low cutback and high cutback values which restrict the amount of overshoot, or undershoot.

How to tune

1.Set the setpoint to the value at which you will normally operate the process.

2.In the ‘Atun’ list, select ‘tunE’ and set it to ‘on’.

3.Press the Page and Scroll buttons together to return to the Home display. The display will flash ‘tunE’ to indicate that tuning is in progress.

4.The controller induces an oscillation in the process variable by first turning the heating on, and then off. The first cycle is not complete until the measured value has reached the required setpoint.

5.After two cycles of oscillation the tuning is completed and the tuner switches itself off.

6.The controller then calculates the tuning parameters listed in Table 4-1 and resumes normal control action.

If you want ‘Proportional only’, ‘PD’, or ‘PI’ control, you should set the ‘ti’ or ‘td’ parameters to OFF before commencing the tuning cycle. The tuner will leave them off and will not calculate a value for them.

AACC 2000 Carbon

54

Nov. 1, 1997

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Contents Copyright Marathon Monitors INC Marathon Monitors Inc Mechanical Installation Cleaning SafetyElectrostatic discharge precautions Electromagnetic compatibilityPower Isolation Safety SymbolsWiring PersonnelVoltage rating Over-temperature protectionOvercurrent protection Conductive pollutionInstallation requirements for EMC Grounding of the temperature sensor shieldRouting of wires Environmental ratings Equipment ratingsElectrical safety GeneralMarathon Monitors Inc Installation Outline dimensions Model Outline dimensions Model 2000 controllerController labels To install the controllerIntroduction Unplugging and plugging-in the controllerRear terminal layouts Model Aacc 2000 rear terminal layoutMarathon Monitors Inc Sensor input connections Module 1, 2Two terminal modules SnubbersFour terminal modules COMDual output modules Connections for Process Value 3 in module position Connections for Process Value 2 PV2Communication module Wiring of 2-wire EIA-485 serial communications link EIA-485 wiringMarathon Monitors Inc Operation 26.0 Front Panel LAYOUTsOP2 Button or Name ExplanationOP1 SP2Alarms Basic operationOperating modes Home display Automatic modeOutput power demand Display unitsManual Mode SetpointParameters and HOW to Access Them List header displaysMarathon Monitors Inc Parameter names Parameter displaysTo change the value of a parameter List 1OFFOFF PID PID.1Fact STDPass Name Description Prob Probe list Process Factor Millivolt input OffsetHydrogen or CO constant Name Description DrA.t TunEDrA AdcRES Pid PID listSEt HcbSetpoint list Input listOutput list CmS Comms listInFo Information list Access List FF.OPAlarms Diagnostic alarms Display What it means What to do about it Shows2b Diagnostic alarms Access Levels Access list header Password entryAccess to Read-only Configuration Configuration password Configuration levelLevel selection Returning to Operator Level Setting operator access to a parameterEdit level Hiding or revealing a complete listPromoting a parameter This sheet intentionally left blank Tuning Parameter Code Meaning or FunctionOne-shot Tuning How to tuneTypical automatic tuning cycle Calculation of the cutback valuesAdaptive tune Manual Tuning Setting the cutback values Proceed as followsIntegral action and manual reset Automatic droop compensation AdcName Description Values Mtr Motor list Min Max Default Motorized valve controlAdjusting the minimum on-time ‘mp.t’ Inertia and backlash settingsMarathon Monitors Inc Enable in configuration level Gain schedulingSet the transfer point Configuration Selecting configuration level Press to enter configurationLeaving Configuration Level Changing the passwordsD1SA Enab REULIN SB.OPRely CMSNone DIG YESPMV H2O InSt Instrument configurationName Description Values Meaning SP.FFProcess value config Input configurationCJC Setpoint configuration VAL.LVAL.H Alarm configuration Values Table a Alarm types ValueAlarm Modes Digital input 1 configuration Action on contact closure Digital input 2 configuration Action on contact closureIMP Alarm relay configuration VfltPflt Comms 1 module config Combining several digital events on to one outputModule config 1A b C1 Module 1 configurationCool 2A/b/C Module 2 configuration For ‘id’ = ‘LoG.i’ i.e logic input use the LA Conf’ list onDisplayed value low 3A/b/C Module 3 configuration SELC Module configuration Module configurationPoint Custom Linearisation VAL.1VAL.8 CAL DC Output Calibration Password configurationExit Exit configuration User calibrationUser calibration User Calibration Enable User Calibration EnableCalibration Configuration List Exit configurationOffset calibration Input list headerCalibration type See table on the right for additional parameters Set OffsetTwo-point calibration Displayed ValueAdjust low-point calibration Select Low-point CalibrationAdjust High-point Calibration Select High-point CalibrationCalibration points and Calibration offsets Name Parameter description MeaningParameter Table Default HY1 Ssel FLT3 Marathon Monitors Inc AL1 Module 2A High Value VAL.1 101 Index Two-point calibration User calibration Aacc 2000 Carbon
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