Control for fluid flow system

Claim 1

Apparatus for supplying an additive to a fluid flowing in a pipe comprising a magnet rotatably supported and driven by said fluid such that it rotates at a speed proportional to the velocity of the fluid, a Hall effect device mounted adjacent said magnet and producing output pulses in response to rotation of the magnet, a digital counter receiving the output of said Hall effect device and counting said output pulses, a comparator having a preset count receiving the output of said counter and having two different output states corresponding to the conditions when said comparator has received less pulses from said counter than said preset count and pulses equal to said present count, a timer receiving an output of said comparator, an electronic switch receiving the output of said timer, a feeder connected to said pipe and receiving an output of said electronic switch and controlled by said comparator to turn the feeder off and on in response to said two states of said comparator, and a container connected to said feeder to supply an additive to said fluid when said feeder is on, and wherein said counter has a reset terminal and said comparator supplies an output to said reset terminal.