PURPOSE: To provide a water level control device capable of stably controlling an objective water level in a water tank which is to be changed with the lapse of time by small pump capacity.
CONSTITUTION: The water level control device is provided with a water tank 1, a water feeding pump 2 for feeding water to the tank 1 through a flow rate control valve 3, a drainage pump 4 for draining water from the tank 1 through a flow rate control valve 5, the 1st flow rate control means (a differential circuit 10, an objective flow rate computing element 11 and a control circuit 7) for controlling either one of a draining flow rate and a feeding flow rate so as to follow up a flow rate found out by the variation (dL/dt) of the objective water level L, and the 2nd flow rate control means (a control circuit 6) for controlling other flow rate (the feeding flow rate or the draining flow rate) so as to allow a water level La to follow up the level L.
JPS56116118A | 1981-09-11 |
Next Patent: AIR PRESSURE CONTROL VALVE