Abstract: A microcontroller directed circuit evaluates volume flows through fluid distribution lines. The control circuit is integrated into a modularized housing designed to retro-fit standard fluid divider valve assemblies. The modular housing includes a plunger-driven magnet positioned to actuate a reed switch in response to divider valve piston reciprocation. The control circuit evaluates the frequency of reed switch actuation pulses to derive intelligible fluid flow related data available for RAM storage or conveyance to peripheral computer devices. In a preferred embodiment, a cavitated cylindrical housing contains a control circuit and a reed switch. A plunger acts as a lever arm to transmit the lateral oscillation of a fluid control piston within a divider valve assembly to a magnetic field source within the housing.