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2.2 OPERATING PROCEDURE WITH FEEDFORWARD

Process Example Template 6-1 applies to Figure FO-1 with its notations. Note that three pair of wires are required between controller pHC and flow controller FC2.

Figure FO-2 shows the same system described above except that the wiring between the two instruments is done with the ICN and requires only one  pair of wire .

Process Example Template 6-2 applies to Figure 9 with its notations.

Figure 4. Break Points Determine Where Gain Will Start to Change, Process, Deviation or Remote Input Adaptive Function .

Figure 5. Both Break Points Can Have Same Value, Process, Deviation or Remote Input Adaptive Function

2.3.1.2 Gain Factors

The value of the gain factor determines if the active gain or reset will increase or decrease, starting from the break points as shown in Figure 7.

If the gain factor is less than I (e.g., 0.875), the gain or reset will decrease. When the gain factor value is 1, the gain or reset will not change. If the gain factor value is greater than 1 (e.g., 2.625), the gain or reset will increase.

2.3 GENERAL DESCRIPTION OF ADAPTIVE GAIN OR RESET FUNCTIONS

2.3.1 Process, Deviation and Remote Input adaptive Gain or Reset functions

The parameters that define the adaptive algorithms for process, deviation and remote input functions are set up in the same manner. A large combination of break points, gain factors and active gain or reset limits can be used to provide many different adaptive algorithms. Because each adaptive algorithm is set up individually, the number of overall controller algorithms is very large. The adaptive functions can be on gain or reset, but not on both simultaneously.

2.3.1.1 Break Points

The location of the break points determines where the gain or reset will start to change as a function of-the adaptive variable as shown in Figure 4. The gain or reset value between the break points is the base gain or base reset and never changes. Both break points can be located at the same range value as shown in Figure 5, or they may be set at different values as shown in Figure 6. When the two break points are set at different values, Figure 6, BP1  must be at a lower range value than BP2. The active gain or reset between the two break points is equal to the base gain or reset (because the gain factor is always 1 between the two break points), while the active gain or reset beyond the break points changes as determined by the gain factors.

Figure 6. Break Points Can Have Different Values, Process, Deviation or Remote Input Adaptive Function

Figure 7. Gain Factor Values Determine if Gain or Reset Rat Will Increase or Decrease From Break Points, Process, Deviation or Remote Input Adaptive Function.

Both gain factors can increase, both can decrease, or either gain factor can increase while the other decreases active gain or reset. The combinations of gain factors and break points can be used to produce a large variety of algorithms.. Some of the possibilities are shown in Figure 8.

The gain factor values are multipliers. The base gain or reset is multiplied by the gain factor for the adaptive gain or reset function. The result is the value of active gain or reset at one, and only one, point on the range. This point, Figure 9, will be 10% downscale from BPI or 10% upscale from BOB, and it establishes the slope of the line in the algorithm.

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Figure 8 . Various combinations of Breakpoints and Gain Factors that can be used to produce a Large Variety of Algorithms , Process , Deviations or Remote Input Adaptive Functions .

Figure 9 . Gain Factors Establish Slope of Algorithm beyond Break Points , Process , Deviations or Remote Input Adaptive Function .

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