Process ControlsCONTROLLERSThe deviation indicator, located left of the setpoint indicator, displays any error (+10%to -10%) between setpoint value and actual controlled variable value. With no error, thedeviation pointer stays at mid-scale, in line with the setpoint index mark. If thecontrolled variable is lower than setpoint, the deviation indicator deflects downward. Ifhigher, the indicator deflects upward. An example of this is shown in Figure 33.Figure 33 Deviation IndicatorThe output meter is the horizontally positioned meter below the deviation and setpointindicators. It indicates controller output signal in percent. This particular controllerranges from zero to 100% current. However, this will correspond to an air signal forpneumatic controllers.Snap-in tabs, above each end of the output meter, indicate the direction the final controlelement moves for a change in the output signal. Tabs normally read "open-close" forcontrol valves and "slow-fast" for variable-speed motors, or other appropriatedesignations.The manual-automatic (M-A) transfer switch, immediately below the output meter, selectsoperating mode of the controller.A manual output adjust knob, in the center of the M-A transfer switch, varies thecontroller output signal in manual mode of operation. The knob is rotated clockwise toincrease the signal and counterclockwise to decrease the signal.The M-A transfer switch has five positions that alter the mode of operation. The indication isprovided by the deviation meter.AUTO. This is the normal position of the M-A transfer switch. It places the controllerin the automatic mode of operation. Also, the deviation meter indicates any deviationbetween controlled variable and setpoint.Rev. 0 Page 49 IC-07
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