Abstract: A system for preparation of variable hemodialysate in which a controllable pump meters multiple fluid sources of dialysate concentrates and water in controlled proportion. The system includes a plurality of cylinder and piston pump assemblies linked together for simultaneous operation. Individual valves connect the separate pump assemblies to the individual fluid sources to be proportioned. A position sensor provides signals indicative of the position of the pistons throughout their stroke cycle, and with a control operates the control valves associated with the individual pump assemblies in accord with functions of piston position and preselected proportioning control inputs, so as to control the volume of fluid metered by each of the pumps during the pump stroke.

Abstract: An improved portable conductivity meter for automatically and rapidly drawing an electrolyte sample and for measuring and providing an accurate output indication of its electrical conductivity, which is independent of temperature variations of the electrolyte. A pen-like dip probe, housing an electrode pair and a thermistor in unique configuration, is designed to rapidly draw an electrolytic dialysate sample whenever the probe is immersed within the electrolyte. A high frequency AC source drives a balanced active measurement circuit, having a reference leg and a measurement leg which contains the electrode pair and the temperature compensating thermistor. The balanced circuit provides measurement and reference output signals of opposite polarity to a summing amplifier which drives a visual conductivity indicator.