Automatic liquid level controller

Claim 1

Apparatus for controlling a pump suspended in a well comprising: a source of periodic acoustic pulses continuously coupled to said well; a transducer coupled to said well producing an output in response to the occurrence of acoustic pulses in said well and in response to the detection of the acoustic pulse reflected from the liquid surface in said well; a clock pulse source; digital counting means; gating means responsive to the output of said transducer for starting the counting of clock pulses by said digital counting means upon the occurrence of an acoustic pulse in said well and for stopping said counting upon detection of the acoustic pulse reflected from the liquid surface in said well; and a digital controller responsive to said digital counting means for controlling said pump, said digital controller including: a high level set-point circuit including a manually settable digital register calibrated in units of depth; a low level set-point circuit including a manually settable digital register calibrated in units of depth; and a comparator, said digital registers and said counting means being connected to said comparator, said comparator being connected to turn said pump on in response to counting clock pulses between said periodic acoustic pulses and said detection of the acoustic pulse reflected from the liquid surface when the liquid in said well exceeds the high set-point level and to turn said pump off in response to counting clock pulses between said periodic acoustic pulses and said detection of the acoustic pulse reflected from the liquid surface when the liquid in said well falls below the low set-point level.