This causes the dose size to automatically vary in proportion to the error and is useful when you want the tank to dose up quickly.
If this is selected then the dose size is specified as both a maximum and minimum dose time. The controller then looks at the size of the error and if large gives large doses but as the EC or pH setpoint is approached, the controller will give smaller and smaller doses approaching the minimum size.
This is useful in irrigating (drip) systems that do not re-circulate as it allows rapid dosing after each irrigation occurs.
This feature is not available with more than 2 part mixes.