Abstract: For a metering vibrating pump in a variable flow rate condition, a system and a device is provided for supplying desired liquid quantities comprising a memory circuit (36) set by a supply or energization starting signal (38), a counter (24) counting a certain pump stroke number detected by a piston position detector (12) for detecting the position of a piston in the pump, a numerical comparator (28) comparing the numbers emitted by the counter (24) with preset numbers formed by a numerical digital combinator (32) for outputting a reset signal for the memory circuit (36); the memory circuit (36) starts the pump operation when it is set and stops the operation when it is reset.