US Patent 9410545 Solid state bilge pump switch

A switch for a bilge pump of a boat includes a pair of probes for providing a probe signal indicating the presence of fluid at the probes, a current sensor for providing a sensor signal indicating electric current of the pump; and a controller programmed to energize the pump when a threshold level of the probe signal indicates the presence of fluid and to de-energize the pump when a threshold level of the sensor signal indicates that the pump is not pumping fluid. The controller can also be programmed to dynamically change the threshold level of the probe signal based on a prior probe signal that indicates changing probe conditions.