The floating control mode is another kind of discontinuous controller action.
Floating control is a special application of two-position control.In this mode,when the process variable increases above the deadband,the controller output drives the controlled device at a constant in one direction.
When the process variable decreases below the deadband,the controller drives the controlled device at a constant rate in the opposite direction.If the PV stays within the deadband,the controller output remains at whatever value it had when first entering the deadband region.
In floating control,the controller output can be any value between 0 and 100% unlike the two position controller,whose output is either 0% to 100 %.
When the process variable increases or decreases to a value outside the deadband,the controller output changes aat a constant rate from its last output value.
Floating control is useful in processes in which the load changes are large but slow to change.
If the rate of change is too rapid,the controller may function more nearly like a two-position controller.