The present invention consists of a method and apparatus providing for the continuous
stream blending, preferably on a
mass ratio basis, of two or more liquids. Each individual liquid
stream is synchronously dosed in precise
mass ratio to a common mixing point. The flow of each
stream is on-off or digital. Repeated
mass ratio doses of defined and matching flow interval, referred to as synchronous digital flow, interspersed with a defined interval of no flow, constitutes digital flow at a net rate sufficient to meet or exceed some required take-away of the blended liquids. In one preferred embodiment, each
dose stream flow is produced and measured by a four element apparatus preferably consisting of a
servo motor and controller, a precision
positive displacement pump, a Coriolis mass meter and a precision flow stream shut-off device. The
servo motor and controller establish and control a periodic and intermittent flow rate necessary to displace a defined mass
dose in a precisely defined flow interval. The flow interval is measured against a precision
millisecond digital clock. The Coriolis mass meter is used only to totalize mass flow to define the desired mass
dose during the defined digital flow interval. The flow stream shut-off device ensures precise delivery of the mass dose to the common mixing point. The flow rate of a stream is automatically adjusted by the
control electronics until the required mass dose is delivered in the defined flow interval.