Abstract: Disclosed is an inductance detector for detecting boundaries between and characteristics of at least two adjoining substances having different characteristics, such as impedance, wherein a coil assembly, which is energized by an alternating current, is electrically coupled to a detector for detecting at least changes in impedance of the coil assembly caused by the boundary proceeding into and through the coil assembly.

Abstract: A universal holder for objects such as test tubes, cuvettes, cells and the like comprising a stationary upright body having a pair of angularly arranged planar surfaces, the surfaces defining a V-shaped recess and a deflectable spring-biased member arranged for pivotal movement against its bias from a normally horizontal disposition extending into the aforesaid recess and the biased member capable of being deflected by the object as it is introduced in the recess. The planar surfaces may have matching elongate notches to provide a purchase for angular bodies, such as rectangular cells. Both the upright body and the deflectable member have slot means arranged to permit a light beam freely to pass therethrough and through the object.

Abstract: The photometer circuit is operative to receive and store a reference voltage which is generated in a photosensor by light which passes through a blank solution in a cuvette and is received at the photosensor. The photometer circuit includes reference voltage input control circuitry for placing the photometer circuit in a receiving and storage mode of operation for a predetermined period of time while the reference voltage is being generated in the photosensor. The photometer circuit includes a comparator having two inputs, a first electronic switch for coupling the output of the comparator to a voltage storage circuit and a second electronic switch for coupling the output of the voltage storage circuit to a voltage run-down circuit.

Abstract: The electrical sensing circuitry includes a power supply and a signal-detecting circuit which are coupled through the resistance of an electrolyte in a liquid in an aperture of a particle-analyzing device between sensing electrodes positioned on either side of the aperture. The liquid containing an electrolyte and the passage of a liquidborne particle through the aperture causes a change in the resistance of the aperture thereby generating a signal which is detected by the signal-detecting circuit. The parameters of the circuit elements are chosen to provide circuit relationships which render the particle-generated signal independent of the diameter of the aperture. This is achieved by utilizing a power source having a low output impedance and a signal-detecting circuit which has a low input impedance for both D.C. and A.C., namely, at the signal frequencies of the signals sensed.