Blood test device and method

Claim 1

A volumetric particle counter for counting relatively nonconductive particles in a fixed volume of relatively conductive liquid test solution comprising a vertically oriented conductivity cell of insulating material having a metering orifice, an internal cavity providing a fixed volume between first and second levels within said cavity the volume between said first and second levels providing a measure of known volume of test solution, a suction connection on said cell communication with said cavity above the second level, a pressure connection on said cell communicating with said cavity above the second level, and a discharge passage from said cell communicating with said cavity below the first level, a support frame for supporting said conductivity cell, an open top beaker for containing a test solution containing particles to be counted, a platform movably supported on said support frame by elevator means to raise and lower said platform so that said beaker in the raised position places sAid test solution containing particles to be counted in fluid communication with said cell cavity through said orifice, vacuum producing means and gas pressure producing means on said support frame, separate valve means, respectively, connecting said suction connection to said vacuum producing means, connecting said pressure connection to said gas pressure producing means and connecting said discharge passage to waste, and each valve means having selectably positionable means for opening and closing said valve means, whereby the valve means connected to pressure and waste may be closed when the valve means connected to the vacuum producing means is opend to permit the test solution to be drawn into the internal cavity of the conductivity cell through the metering orifice and whereby these valve conditions may be simultaneously reversed to urge the test solution out to waste below the electrodes but above the orifice, an external electrode outside the conductivity cell in position to extend into the test solution in a container on said support means, an internal electrode inside the cavity of the conductivity cell, a counter circuit, into which said first internal and external electrodes are connected and which is completed by conductive liquid test solution between said electrodes, to count each pulse occurring as the result of variation in impedance of the circuit which occurs as a particle in the test solution passes through the orifice thereby reducing the conductive crosssection area of said orifice, first and second control electrodes positioned at said first and second levels within said cavity to sense when the test solution reaches, respectively, said first and second predetermined levels in said cavity, counter selection means connected to said first and second internal control electrodes and connected to the counter circuit to permit output of a selected count only when the test solution reaches said first level and terminating said selected count when the test solution reaches said second level, said selected count being representative of counted particles within said known volume, and count display means responsive to the output of the counter means and displaying a particle count proportioned to the count for said fixed volume.