Omega Engineering CN 79000 manual Set Point 2 Tracking, Operation of Self Tune Function

Set Point 2 Tracking

Some applications will call for Set Point 2 to follow or 'track' the setting for Set Point 1. This can be done by changing the S2tsetting in the Secure Menu (edit set for 2 or 3). For a tracking SP2, set S2t to dE.

The Factory Default setting for S2t is ABS, making SP2 completely independent of SP1.

When setting SP2 value when Set Point 2 is programmed as deviation (S2t

=dE), set the difference in value from the Set Point 1 (SP1) desired. For example if Set Point 2 is required to be 5 degrees below the SP1, then set SP2 to -5. If Set Point 2 is required 20 degrees above the SP1, then set SP2 to 20. If SP1 is changed, the SP2 setting will continue to hold the same relationship as originally set.

When setting SP2 value when Set Point 2 is programmed as absolute (S2t

=AbS), simply set the value at which the alarm is to occur.

OPERATION OF SELF TUNE® FUNCTION

Self Tune® allows automatic selection of the necessary parameters to achieve best control operation from your C N 74000 Series control. If you are using the control output as a simple on-off function (e.g. Out1 set for OnOF), none of the following will apply.

Theory of Operation

The Self Tune function calculates the Pb1, rES1, and rtE1 parameters under thePID1 tunEselection,Pb2,rES2, andrtE2parametersunder thePID2 tunE selection, the Fbd1 and Frt1parameters, and the Fbd2 and Frt2 parameters, as shown in the Secondary Menu . These values are determined by measuring the response of the process connected to the control. When Self Tune is started, the control temporarily acts as an on-off control. While in this mode the control measures the overshoot and undershoot of the process, and the period of the process (the time from peak value to the next peak value). These measurements are collected over a period that lasts three periods of overshoot and undershoot. The data collected over this time is then compared and calculated into final PID and Fuzzy Logic values. The effect of Fuzzy Logic on the process is still controlled by the Fi 1 and Fi 2 (fuzzy intensity) settings. If Fi 1 or Fi 2 is 0, the Fbd1, Frt1, Fbd2, and Frt2 will be calculated, but will have no effect.

ThecalculationsforZone1andZone2arecompletelyindependent. Eachzone has separate Self Tune and Fuzzy Logic parameters.

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