Abstract: A control system for automatically maintaining a predetermined water level in a swimming pool includes a multi-contact water level sensor unit mounted on an exposed sidewall of the pool. The sensor unit is vertically adjustable within a stationary mounting bracket to enable user adjustment of a selected normal water level. A single sensing contact on the sensor unit senses the presence or absence of water at the selected normal level. A monitoring circuit associated with the sensor unit interrupts operation of the control system in the event that the sensor unit is disconnected. Additional water level sensing contacts open a dump valve to preclude overflow of the pool in the event of a high water condition, and interrupt operation of recirculation pump apparatus associated with the pool in the event of a low water level.

Abstract: A control system for automatically maintaining a predetermined water level in a swimming pool includes a multi-contact water level sensor unit mounted on an exposed sidewall of the pool. The sensor unit is vertically adjustable within a stationary mounting bracket to enable user adjustment of a selected normal water level. A single sensing contact on the sensor unit senses the presence or absence of water at the selected normal level. A monitoring circuit associated with the sensor unit interrupts operation of the control system in the event that the sensor unit is disconnected. Additional water level sensing contacts open a dump valve to preclude overflow of the pool in the event of a high water condition, and interrupt operation of recirculation pump apparatus associated with the pool in the event of a low water level.

Abstract: Circuitry for automatically controlling the water level of swimming pools with a multi-level detecting sensor for directly sensing the pool water. A low voltage oscillator in the input portion of the circuitry detects the presence of water above or below each level sensing electrical contact of the sensor by a change in oscillator amplitude in response to impedance from the contact to ground. Signal threshold circuitry changes in output signal in response to the amplitude of the oscillator signal. Delay circuitry integrates the output of the threshold signal to avoid responding to spurious changes in water level, such as wave action in the pool. Monitor circuitry disposed between the delay circuitry and the water fill, water dump, and pump control circuitry monitors signals received from the sensor or generated by the input circuitry to detect any malfunctions in the sensor or the control circuitry, such as improper sequence of the water level signals, to disable further filling of the pool.