Abstract: Sample handling apparatus for circulating one or more sample holders along a rectilinear path in a sample holder storage compartment and past an operating station at which the holders may be removed from and then returned to the compartment. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. Lateral drivers engage the holders in longitudinal stop positions at opposite ends of the conveyors and drive them laterally between conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. A movable sample compartment divider between the conveyors is indexed in synchronism with the lateral drivers to engage and stabilize the sample holder at the operating station.

Abstract: Sample handling apparatus for circulating one or more sample holders along a rectilinear path in a sample holder storage compartment and past an operating station at which the holders may be removed from and then returned to the compartment. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. Lateral drivers engage the holders in longitudinal stop positions at opposite ends of the conveyors and drive them laterally between conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. A movable sample compartment divider between the conveyors is indexed in synchronism with the lateral drivers to engage and stabilize the sample holder at the operating station.

Abstract: There is disclosed a method and apparatus for implementing a narrow band rejection filter utilizing a liquid crystal cell. A liquid crystal cell is positioned in the path of a light beam between a pair of crossed or parallel polarizers with the optical axis of the cell at a 45.degree. angle to the optical axes of the polarizers. A voltage is applied to the cell to tune the cell to reject a given wavelength and to pass other wavelengths. In order to reject the given wavelength and pass all other wavelengths, the order of the cell is stepped to maintain rejection of a fixed wavelength and the detected signal from the light passing through the cell is averaged.

Abstract: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

Abstract: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

Abstract: Method and apparatus for measuring the magnitude of a varying analog signal and for displaying a close approximation of a final stabilized value before the signal reaches stabilization. An analog-to-digital converter converts the analog signal to corresponding digital pulse signals and the digital pulse signals are displayed to an operator. Automatic display-hold circuitry determines the pulse count difference between successive pulse count signals separated by a predetermined time interval, compares the difference to predetermined value, and, when the predetermined value is reached, generates a control signal which locks the displayed value and prevents the display from updating as the analog signal continues to vary. The difference between pulse signals is taken by storing the first signal in an up/down counter and decrementing the counter in response to the second signal.

Abstract: A fluid dispenser including a syringe having a reciprocating syringe plunger for controlling syringe fluid intake and discharge and a traveling slide connected to the plunger for driving the plunger. The traveling slide is bearing mounted in sliding relationship on a fixed shaft and is driven therealong by a pinion gear engaging a rack secured to the slide.

Abstract: An automatic spectrum scanning technique for use in a proportional counting instrument, such as a gamma counter or liquid scintillation counter, by means of which a pulse-height or energy spectrum of a sample can be obtained automatically and without multichannel instrumentation. A pulse-height analyzer in the counting instrument has its upper and lower discriminator limits set to define a relatively narrow counting window, and the limits are successively changed to scan the window across the energy spectrum and thereby obtain an accurate measurement thereof. Counting at each increment of the scan is continued for a preselected maximum time interval, but is quickly terminated if the count rate falls below a preselected low threshold value, and is terminated early if the count rate is relatively high, i.e., if the statistical error value associated with the count is relatively low.

Abstract: A nephelometer including an optical excitation system for directing light through a first window area into a cylindrical glass container and an optical detection system for quantitatively monitoring light scattered by a substance within the container and passing therefrom through a second window area. The optical detection system includes a lens system in optical alignment with the second window area and focused on an optical dark region on an inner wall of the container opposite the second window area. The optical dark region is free of internal light reflections. Therefore, the light monitored by the detection system is scattered light from the substance substantially free of internal light reflections representing background error.

Abstract: A signal conditioning circuit for extracting unipolar noise from an analog input signal by isolating the unipolar noise component and subtracting it from the input signal. The circuit includes a coupling capacitor receiving the analog signal and an ideal clamp connected to the capacitor output terminal to clamp the capacitor to an edge of the unipolar noise signal. The capacitor is thus prevented from charging toward a level representing an average value of the unipolar noise and hence functions to pass the noise undistorted for subtraction from the analog input signal. The clamp comprises an operational amplifier having a first input terminal connected to the capacitor output terminal and a second input terminal connected to a source of reference voltage. A diode is connected in a feedback path between an output terminal of the amplifier and the first input terminal thereof.

Abstract: A voltage regulator circuit including an operational amplifier having supply voltage terminals connected to a source of unregulated supply voltage and a two-terminal, essentially zero temperature coefficient, semiconductor bandgap voltage reference circuit connected in a negative feedback path between the output terminal and one input terminal of the amplifier. The amplifier provides a constant current source for the bandgap voltage reference circuit, and the amplifier and reference circuit cooperate to establish a regulated output voltage at the amplifier output terminal. A resistive divider network is connected in a positive feedback path between the output and a second input terminal of the amplifier to establish the value of the regulated voltage within a range of values between the bandgap voltage and the unregulated supply voltage.

Abstract: A method and apparatus for inhibiting measurement of nuclear radiation in a scintillation counter during periods of excessive background radioactivity produced, for example, by cosmic energy surges impinging on the scintillation counter. The count rate of a radioactive source or sample being measured is monitored and detector means are provided for detecting the occurrence of an energy surge exceeding a predetermined energy level. When a surge is detected, inhibit means inhibits counting for a time period which varies inversely with the count rate.

Abstract: A fluorometer for analyzing a sample by detecting light induced radiation emitted from the sample including apparatus for generating a narrow slit of light in the plane of the sample and transfer apparatus including a light shield having an acutely angled port immediately adjacent the sample for collecting radiation emitted by the sample and transmitting same via a light pipe to a remote detector.

Abstract: Detector apparatus for a laser light scattering photometer of the type for measuring radiant power scattered from a sample at a selectable angle with respect to the direction of an incident beam of radiant power and for measuring radiant power transmitted through the sample in the direction of the incident beam. The improved detector apparatus receives and detects the scattered power and the transmitted power and provides an output indicative of the radiant power of each independent of the spatial properties of the two beams. The detector apparatus comprises a planar diffuser spaced from and parallel to the large area end-window of a photomultiplier detector, the diffuser diffusing the energy over the surface of the end-window. The diffuser and photomultiplier detector are positioned within a cylindrical container which is enclosed at the end thereof in front of the diffuser, the enclosed end of the container having an aperture therein through which the beams pass to the diffuser.

Abstract: An electrochemical combination electrode assembly particularly adapted for measuring the pH of body portions of a living subject, such as skin, hair, and the like, and which can be operated in any vertical, inclined or horizontal orientation. The assembly comprises a pH-indicating glass electrode supported within a tubular plastic container and includes a generally flat, pH-sensitive structure at a sensing end of the assembly. Conventional indicating and reference half-cell electrodes are supported in separate reservoirs of the assembly containing internal and reference electrolytes, respectively. The upper ends of the reservoirs are sealed by elastomeric plugs which compensate for differing coefficients of expansion within the assembly and coact with the electrolytes to prevent formation and migration of air bubbles to the sensing end of the assembly.