Abstract: A method of identifying an operating position of a multiple-position filter changing mechanism situated in an optical path of a spectrophotometer by detecting and measuring a spectral characteristic(s) of light passed along the optical path to the spectrophotometer detector for one or more operating positions of the filter mechanism and comparing the measured spectral characteristic(s) with stored spectral characteristic information for one or more operating positions of the filter mechanism.

Abstract: Moderately narrow band, tunable, birefringent filters are disclosed using zero-twist liquid crystal cells as variable retarders in a Lyot-type birefringent filter. These filters can achieve analytically useful levels of resolution and stray-light ratios for costs that are competitive with prism and grating monochromators. These birefringent filters can be tuned and/or rendered opaque by the application of a suitable voltage to the cells. Thus, a variety of different optical instruments can be constructed with no moving parts. Power requirements are negligible. A useful filter can be designed to occupy a volume less than one cubic inch. These properties render such a filter ideally suited to microprocessor control.

Abstract: A centrifuge rotor is provided which has a circumferential wall and a plurality of spaced arms which radiate outward from the center to the circumferential wall. A plurality of buckets are mounted on the rotor, one between each arm. Each bucket has two outwardly extending pivot pins situated on a common axis. A plurality of hangers are mounted in the spaced arms of the rotor. Each hanger comprises an elongated housing containing an opening which is transverse to the longitudinal dimension of the housing for receiving the pivot pin of a bucket. A longitudinal bore intersects the opening and contains a spring for exerting a clamping force on the pivot pin when the rotor is stopped. This prevents the bucket from rocking when being loaded or unloaded, but does not prevent the bucket from pivoting to a horizontal position when the rotor is rotating, nor does it prevent the bucket from resuming a vertical position when the rotor is stopped.

Abstract: A container for comparative testing of a sample substance. The container includes a plurality of side-by-side compartments into which a sample substance may be injected. A cover and seal protect the compartments from the outside atmosphere. A sample substance may be injected through the cover and the seal which then reseals itself upon withdrawal of the injecting probe. Level indicator lines on each compartment provide an indicator to ensure the exact amounts of substance being placed in each compartment.

Abstract: A magnetic stirring arrangement for stirring sample material held within a cylindrical glass sample container for assay. A stirring element within the container is retained in a fixed orientation by an external magnetic field. The container and the contents thereof are rotated in place causing the container contents to be stirred by rotational motion around and past the fixed stirring element.

Abstract: A centrifuge tube holder capable of being manually assembled and disassembled without separate tooling to provide not only ease of cleaning, but also interchangeability of parts to accommodate various sized centrifuge tubes. The tube holder arrangement provides proper support with a minimum of parts to create a lighter weight assembly for use in a centrifuge rotor.

Abstract: Bargraph displays wherein the illuminable bar segments are formed by winding filamentary conductors upon a mandrel.

Abstract: An electrical device consisting of a package 10 comprising a base 11 and a lid 15 and an operation element 17 contained within the package. A particle getter 19 is disposed on the lid 15 for entrapping and retaining foreign particles contained within the package 10. A method for protecting the operational element 17 of such an electrical device from the particles is disclosed wherein a polysiloxane material is partially cured with less than about 9 parts of a suitable curing agent to 100 parts of polysiloxane resin to a non-flowing, particle entrapping and retaining condition and the partially cured material is secured within the package.

Abstract: An improved assembly for holding a filter element so as to define a filter assembly for removing particulate matter from a sample gas stream. First and second housing sections mount and enclose a replaceable filter element. An annular wall extending between the housing sections divides the interior of the housing into a first region open to an inlet, and a second region open to an outlet, the filter element being mounted in the second region, downstream of the wall. A plurality of openings through the wall assure that particulate matter collects evenly over the surface of the filter element. In this manner, the useful life of the filter element is greatly extended.

Abstract: An integrating analog-to-digital converter for converting an input signal having an amplitude representing an analog quantity into a digital signal representing the quantity wherein the input signal may have either a positive or negative polarity and the converter automatically generates the digital signal without regard to such polarity. The converter uses a single circuit for charging and discharging a capacitor such that any errors or offsets occurring upon charging are fully and automatically compensated for during discharging so as to provide for automatic zeroing of offset errors without separate autozeroing circuitry.

Abstract: A method and apparatus for removing a flexible layer from a substantially flat mold or other surface. A curvilinear removal head, including a vacuum manifold holding one end of the flexible layer, pivots to peel the flexible layer from the mold.

Abstract: An apparatus for compensating for changes in the mass flow rate of a sample gas stream in gas analysis instruments having outputs that are calibrated in terms of the concentration of a component of the sample stream. In instruments in which a pressure regulated sample gas stream is applied to a detector assembly through a flow restrictor such as a sample capillary, a gas flow sensor is connected in series with the flow restrictor to develop a correction signal that varies in accordance with the mass flow rate of the sample stream. A correcting circuit combines the correction signal from the flow sensor with the output signal from the detector assembly to produce a corrected output signal that correctly indicates the concentration of the component of interest.

Abstract: A centrifuge holder to inhibit movement of a centrifuge machine caused by a rotor within the centrifuge coming off the drive spindle. The holder apparatus is designed in such a manner that the centrifuge machine can be placed on or removed from the holder without the need of any separate tool. Tab members of the holding apparatus are received within spaced apertures located in the bottom of the centrifuge.

Abstract: Apparatus for indicating when an analog or digital input signal remains sufficiently stable for a predetermined length of time. The apparatus continuously monitors the input signal instead of sampling it only at discrete points in time. The apparatus includes a memory which stores the value of the input signal at the time of the most recent occurrence of a reset signal, a comparator which produces the reset signal whenever the input signal differs from the memory signal by an amount greater than that allowed by a predetermined comparison criterion, and a timer for indicating that the input signal is stable when the reset signal has not been produced for a time exceeding the predetermined length of time.

Abstract: A fixed angle tube carrier is provided for use with externally shouldered sample tubes and a centrifuge rotor having formed therein a plurality of symmetrically disposed vertical slots in its outer peripheral surface. The slots are formed in the shape of a "T" and adapted for sliding engagement with a tube carrier. The tube carrier comprises a vertically elongated member having a "T" shaped cross-section which is adapted for sliding engagement with the slots of the rotor. The carrier contains a plurality of circular recesses which are open at each end and adapted for holding an externally shouldered sample tube. The longitudinal axis of each recess is disposed radially of the vertical axis of the rotor and at an angle less than 90.degree. thereto.

Abstract: A sensor mechanism for measuring a property of a fluid which must not be allowed to escape into the environment. A sensor housing provides a chamber from which a sensing element may be extended into contact with the fluid to be measured, and into which the sensing element may be retracted prior to being sealed off from the fluid. When the sensing element is in its retracted position, the closure of a valve seals the chamber off from contact with the fluid. A purging inlet and a purging outlet allow the interior of the sensor housing to be purged of traces of fluid trapped therein by the closure of the valve, prior to the time that the sensor housing is disassembled for the servicing or replacement of the sensing element. An improved sealing arrangement allows the interior of the sensor housing to remain sealed off from the environment without the use of sliding seals. An improved cleaning arrangement allows the sensing element to be cleaned without removing it from the sensor housing.

Abstract: A circuit for measuring the root-mean-square (RMS) value of an electrical signal. The output may be linear or logarithmic. The circuit uses devices with logarithmic voltage/ current characteristics (usually transistors), and allows the logarithmic devices to be connected directly together without intervening operational amplifiers. In its simplest form, the invention consists of a rectifier circuit, four transistors and a capacitor.

Abstract: A single beam spectrophotometer is conditioned to automatically scan a sample across a wavelength scan range and to measure the sample at selected wavelengths within the range. Methods of setting output signal gain, adjusting signal gain for a selected wavelength range, and automatically scanning and measuring the sample are disclosed.

Abstract: A centrifuge rotor for carrying a plurality of centrifuge tubes at a fixed angle with respect to the spin axis of the rotor wherein the rotor has a containment annulus located above the tube cavities in the rotor for containment of any excess fluid from the centrifuge tubes during centrifugation. The containment annulus is designed in such a manner that it will receive all possible excess fluids from the centrifuge tubes during centrifugation and none of the excess fluid will contact or exert pressure on the rotor lid.

Abstract: A method and apparatus for monitoring flow rate through a conduit. A flow number indicative of the flow rate of a liquid through the conduit is compared with a preselected reference number. The actual liquid flow through the conduit provides a clocking signal which determines the time span during which a count signal, indicative of the intended flow rate into the conduit, is accumulated thereby providing the flow number.