Abstract: A method for determining motional branch current in an ultrasonic transducer of an ultrasonic surgical device over multiple frequencies of a transducer drive signal. The method may comprise, at each of a plurality of frequencies of the transducer drive signal, oversampling a current and voltage of the transducer drive signal, receiving, by a processor, the current and voltage samples, and determining, by the processor, the motional branch current based on the current and voltage samples, a static capacitance of the ultrasonic transducer and the frequency of the transducer drive signal.

Abstract: The present device includes a recoiling roll of screening in a shape of an elongate rectangular web which is affixed to a vertical, rotatable spool at one end and a wand collar at the other. The screen roll is vertically oriented on a mounting frame which is affixed to the side of the pool, preferably adjacent to the automatic skimming water trap. The device may also include an outer canister with wiper brushes for wiping away debris which has been accumulated on the screening as it is retracted.