Abstract: The invention concerns a circuit for the determination of the concentration of any component of a liquid containing three different components having different optical properties, for the determination of the concentration sum of all components and of one other component, for the determination of the product and of the quotient which is formed by the third component, and for the calculation of the blood volume per minute of the heart. One or more light sources, a light sensing element, an optical filter and a lens are disposed in the circuit, and also power supply circuits and control circuits. To these are added a signal converting unit or a sensing system operating on three wavelengths other than the isobestic points or on a range containing these points, containing optical measurement channels, and measuring on the transmission or reflection principle.The signals delivered by the three-channel sensor or by the signal converter, as the case may be, are processed by logarithmatic circuits.
Abstract: The conductivity cell is utilized in a particle study device of the type wherein liquid electrolyte containing particles is caused to traverse an electrical sensing zone of small dimensions, sensing electrodes being located on either side of the sensing zone. The conductivity cell includes two electrodes situated in the electrolyte and being coupled to an electrical sensing circuit including the sensing electrodes. The resistance across the sensing electrodes and the resistance across the conductivity cell electrodes are connected in series with the power source and function as a voltage divider. The junction between the two resistances is coupled to a signal detecting amplifier so that a change in the conductivity of electrolyte will cause a change in both of the resistances whereby the voltage at the junction between the two resistances is essentially constant.