Abstract: Systems and related methods pump fluid through a pump having a stroke volume. The systems and methods employ gravimetric control measures to monitor fluid flow through the pump. An actuator interacts with the pump during a stroke interval (TStroke) to pump fluid through the pump. The systems and methods couple a receptacle to the pump, to either dispense fluid into the pump or to receive fluid from the pump. The systems and methods detect changes in weight of the receptacle over a sample time period. The systems and methods achieve a desired flow rate (QDesired) by deriving an actual flow rate (QActual) by sensing changes in weight of the receptacle over the sample time period, taking into account the density of the fluid, and adjusting the stroke interval based upon QActual so that QDesired is achieved.

Abstract: A liquid level presence detection circuit includes a selectively gatable TRIAC serially connected with a load and triggered into conduction by twin sensitive-gate SCR's connected anode-to-cathode with the gates of the SCR's connected to voltage divider circuits which provide gating current to the SCR's in response to the presence of a conductive liquid bridging the two spaced apart contacts of a liquid presence detecting probe. The circuit is used in wet-niche type lamp assemblies that provide underwater illumination in swimming pools and the like and in which cooling is effected by the surrounding liquid. The detection circuit advantageously interrupts the flow of electrical energy to the lamp when the level of surrounding liquid falls below a predetermined level to prevent over-temperature operation of the lamp and consequent damage thereto and resumes the flow of electrical energy to the lamp when the level of the surrounding liquid increases to a safe level to permit adequate cooling thereof.