POINT LEVEL: Product level distance measured from the tank or vessel’s bottom.
HIGH LEVEL: Maximum level at which “vessel full” indication is required.
LOW LEVEL: Minimum level at which “vessel empty” indication is required.
HIGH HIGH LEVEL: Above maximum expected level, can be an additional high alarm set point to initiate emptying of a tank.
LOW LOW LEVEL: Below minimum expected level, can be an additional low alarm set point to initiate filling of a tank.
PUMP CONTROL LOGIC: When applied to overhead tank level control, the pump is STOPPED if the level is equal to or greater than the maximum desired level and does not RESTART until the level is equal to or less than the minimum desired level. Thus the level is maintained between the minimum and maximum point levels.

If applied to sump level control, the pump is STOPPED when the level is equal to or less than the minimum desired level and RESTARTED when it is equal to or greater than the maximum desired level. Thus the level is maintained between the minimum and maximum desired levels.