Describe two position and floating control mode?

Question

Describe two position and floating control mode?

Answer 1

In a 2 position control, a liquid level in a tank is under a float control system, and is such that, when the liquid rises to a certain level, a float switch shuts down a supply valve or pump.

When falling, again at a specific level, the float switch will re-open the valve or re-start the pump.

A floating control will operate a control valve which, as level rises and falls will throttle down or gradually open a level control valve in the inlet (or outlet) line, thereby controlling the level at a pre-set height in the tank. The systems I've worked on (for many years) are mainly Pneumatic in operation.

(Electrical and Hydraulic systems are also in use).

Answer 2

Sounds similiar to 'bang on, bang off' versus 'proportional' control.

Most thermostats operate in two positions: on or off.  If the ambient temperature rises above the set point, 'bang', the thermostat turns on.  If it drops, 'bang', it turns off the heater.  That's two position.

Proportional is like the valve on your toilet tank.  It's goal is to maintain the level in the tank at full.  As the water rises, the valve slowly closes 'proportional' to the water level.