Open and Closed-Loop Feedback Systems:
Problems with Adding Bias Manually

Several problems occur when the bias is changed manually in the controller. One problem with leaving the bias value in the controller is that if a new SP such as 120°F is needed, the amount of bias will not be enough, and it will have to be increased. Conversely, if the SP was lowered to 90°F, the amount of bias would be too much and the temperature would overshoot. This means that the bias will need to be changed for every SP. Since the technician is present to enter the new SP, the bias can be changed at that time.

Another problem with putting bias in the controller and leaving it in is that it will be added to the output signal from the very start when the SP is changed. This would cause the output to change at a faster rate than it normally would.

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