Abstract: A flow cell for use in an analytical system of the type that may be used to test water samples for specific analytes. The flow cell reduces or eliminates the effects of backpressure on a liquid stream passing through the flow cell. This allows a sensor to be incorporated with the flow cell and enables the sensor to provide consistent output with respect to the analyte being tested without introducing signal error due to backpressure fluctuations.

Abstract: An electrochemical sensor structure includes a housing having an inner surface defining a housing cavity. The sensor also has an inner body having an outer surface. The outer surface of the inner body and the inner surface of the housing have engaging portions which directly engage one another to form a channel therebetween. The channel defines an ionic junction in the sensor.

Abstract: A gas chromatograph includes a manifold having a plurality of gas conduits formed therein. A valve module includes a support, a first valve mounted to the support and having a plurality of ports, and a column coupled to the support and being in communication with a port in the first valve. The valve module is pluggably engagable with the manifold. A detector is coupled relative to the column to detect gasses expelled from the column.

Abstract: An analyzer for analyzing chemical properties of a specimen using optical coupling and sensing, has a narrow band light source and an optical probe that is in contact with the specimen. Detectors are used for providing electrical outputs as a function of a parameter of the specimen, and an optical path couples light from the light source to the probe and also couples Raman scattered light from the specimen and Rayleigh scattered light from the specimen to separate detectors. An analyzer circuit is coupled to the detectors to provide outputs as a function of the electrical signals received, and one of the detectors is connected to a signal conditioning circuit for controlling the input of the light source and includes an asymmetric discrimination circuit configured to distinguish positive going fluctuations from negative going fluctuations in the output from the detector.

Abstract: An industrial process sensor includes a proximal end, a distal end, a longitudinal axis and an outer diameter surface. A cam follower surface is recessed into the outer diameter surface. A diameter reduction is formed on the outer diameter surface, between the cam follower surface and the distal end. The diameter reduction defines an annular process sealing shoulder that faces the distal end and lies in a plane intersecting the longitudinal axis. A sensor element is carried at the distal end. A cable is electrically coupled to the sensor element and extends from the proximal end.

Abstract: A solid electrolyte gas analyzer includes an analyzer circuit housed in an electronics housing and a probe housing for immersion in the gas of interest. The electronics housing mounts directly to the probe housing, preferably through a standoff. The analyzer circuit is powered by an AC line input and includes a switching power supply to convert the AC line input to DC power useable by the analyzer circuit. The analyzer circuit also includes a heater circuit controlling a heater in the probe housing. The power supply and the heater circuit automatically adjust to different AC line input voltage levels. The switching power supply efficiently supplies DC power to other portions of the analyzer circuit with little heat generation.

Abstract: A sample immersion probe is disclosed which has an ATR (attenuated total reflectance) element at its tip. The ATR is so shaped that radiation exiting the probe will travel in paths parallel to radiation entering the probe. The angles of incidence of radiation on the ATR surface (or surfaces) which permit partial absorption by the sample material are greater than 45.degree.. At least one of the ATR surfaces in contact with the sample has a fully reflecting coating which prevents radiation absorption by the sample at that location. The ATR shape may be symmetrical or non-symmetrical with respect to the axis of symmetry of the probe. The radiation entering the probe may be in a separate light guide (i.e., path) from the radiation exiting the probe; or the entering and exiting radiation may be in the same light guide (path).

Abstract: A solid electrolyte gas analyzer is equipped with a diagnostic circuit that intermittently measures an impedance of the solid electrolyte measurement cell as an indication that the cell is in need of calibration or replacement. The diagnostic operation is performed on the cell in situ, i.e., while the solid electrolyte cell is exposed to the gas to be measured and heated to a controlled elevated temperature. Preferably the cell impedance is measured at a predetermined frequency by injecting a modulated current through the cell and measuring the resulting voltage drop.

Abstract: A method and apparatus for providing output emission data corresponding to output emissions from a source of emissions includes a sensing emission monitoring system that senses the output emissions directly from the source of emissions and a predictive emission monitoring system that predicts the output emissions from the source of emissions. The sensing emission monitoring system provides a first set of output values indicative of the output emissions, while the predictive emission monitoring system provides a second set of output values indicative of the output emissions. The system checks the operating state of the sensing emission monitoring system and generates output emission data from the first set of output values if the sensing emission monitoring system is operable and from the second set of the output values if the sensing emission monitoring system is inoperable.

Abstract: An instrument that analyzes chemical properties of a specimen using optical sensing provides a laser source with an optical fiber channel that carries light from the source to a probe. The probe has a receiving optical fiber and has an emitting optical fiber that carries Raman-scattered light from the specimen. The emitting optical fiber has a metal buffer layer. A spectral detector receives light from the receiving optical fiber in the probe. A filter module includes a filter that transmits the wavelength of the laser source but blocks wavelengths longer than the source between the source and the emitting optical fiber or the probe. The filter module is coupled to the probe by a linking optical fiber.

Abstract: An apparatus for measuring ion concentration of a solution includes an ion sensitive field effect transistor (ISFET), a reference device, an ISFET control circuit, a memory, a measurement circuit and a diagnostic circuit. The ISFET has a drain, a source, an ion sensitive gate region and a plurality of device characteristics. The reference device is separated from the gate region by a sample solution. The ISFET control circuit is coupled to the ISFET and operates the ISFET at a drain-source voltage V.sub.DS and at n successive drain currents I.sub.Di and corresponding gate-source voltages V.sub.GSi, wherein i is an integer from 1 to n and n is an integer greater than 1. The memory stores the plurality of device characteristics and the n successive drain currents I.sub.Di and gate-source voltages V.sub.GSi. The measurement circuit measures ion concentration of the solution as a function of at least one of the n successive drain currents I.sub.Di and gate-source voltages V.sub.

Abstract: The method and apparatus for measuring a content of vaporous hydrogen peroxide in a gaseous medium within an enclosure includes a irradiating a portion of the gaseous medium with light, measuring an absorbance of light in a selected near-infrared wavelength range, and calculating the content of vaporous hydrogen peroxide from the measured absorbance of light.

Abstract: An apparatus for sequentially pyrolyzing a plurality of samples held in sample tubes comprises a substantially vertical passage through which tubes carrying the samples may be passed; an upper gas-tight valve for closing off the upper end of the passage; a lower gas-tight valve for holding a sample tube in the passage; a distribution valve directing purge gas and carrier gas to the top end of the passage and for passing pyrolyzed sample from the bottom of the passage to an analytical device; and an electrical heating element for heating the passage to temperatures at which a sample will be pyrolyzed.

Abstract: A photoionization detector includes a brittle substrate having a void micromachined therein with a void inlet and a void outlet. First and second electrodes are disposed in the void. An ultraviolet transparent member covers at least a portion of the void in which the electrodes are disposed. A gas sample passes through the void and is exposed to ultraviolet radiation from a UV source. Ionization of the sample is measured as current flowing between the electrodes.

Abstract: An Ion-sensitive Field Effect Transistor (ISFET) sensor for sensing ion activity of a solution includes a substrate and an ISFET semiconductor die. The substrate has front surface exposed to the solution, a back surface opposite to the front surface and aperture extending between the front and back surfaces. The ISPET semiconductor die has an ion-sensitive surface with a gate region. The ion-sensitive surface is mounted to the back surface such that the gate region is exposed to the solution through the aperture.

Abstract: The invention relates to a fiber-optic coupled diffuse reflectance probe that is adapted to detachably connect to a bifurcated fiber bundle. The probe includes one or more lenses for imaging the bundle onto a target with more space between the bundle and the target than otherwise possible. The collecting lens adjacent to the bundle preferably has a reflection stop which diverts reflected light away from the bundle to minimize the problem of stray light. The preferred probe also uses an objective lens to increase the distance between the bundle and the target. The rays emerging from the collecting lens will diverge or spread because of the finite diameter of the transmitting fibers in the bundle.

Abstract: Methods and apparatus for: (1) inputting economic variables expected to influence future asset values and asset-specific variables; (2) estimating financial statements, future asset values, and tentative asset NPVs using estimated economic variables and estimated asset-specific variables; (3) estimating different financial statements, future asset values and current asset NPVs assuming different estimates of the economic variables that affect asset values; and (4) processes to: (a) equate; or (2) reduce to acceptably small numbers the differences between: (i) the risk measures, terminal values, default premiums, and risk premiums used to determine current values, and (ii) risk measures, terminal values, default premiums, and risk premiums implied by the estimates of economic and firm-specific variables.

Abstract: A gas chromatograph includes a manifold having a plurality of gas conduits formed therein. A valve module includes a support, a first valve mounted to the support and having a plurality of ports, and a column coupled to the support and being in communication with a port in the first valve. The valve module is pluggably engagable with the manifold. A detector is coupled relative to the column to detect gasses expelled from the column.

Abstract: A modular analyzer system consists of a control device and one or more functional analyzer modules linked to the control device. The analyzer modules include FID, NDIR, chemiluminescence and paramagnetic analyzers. Each analyzer module includes a microprocessor having all menus necessary for the operation of the analyzer. Menus are coded and transmitted in real time by providing the control device with a dictionary of menu phrases which are coded and the codes maintained in a code index at each analyzer module and at the control device. Since menus are maintained at the analyzer module and not transmitted until called for, there is no need to store specific menus at the control device. New modules can be easily added to the system and any phrases not already included in the phrase dictionary are downloaded to a supplemental dictionary when the new module is added. Data is displayed in the form called for by the analyzer menu and data from several analyzer modules can be displayed simultaneously.

Abstract: A sensing apparatus for spectral analysis in which the sensing head is bi-layered. The layer contacting the sample is formed of corrosion-resistant material, e.g., diamond. It is engaged by a supporting layer formed of infrared transparent material, e.g., zinc selenide through which radiation passes on its way to and from the sample-contacting layer. In order to avoid non-linearity in the sample absorbance results, incoming paraxial rays are all reflected in such a way that they are reflected at the same angle, and the same number of times, from the sample contacting surface of the corrosion resistant layer. The incoming rays may be reflected at a conical surface, or at a flat rooftop-like surface. The exiting rays are preferably reflected so that they are parallel to the incoming rays. Where a conical reflecting surface is used, it may be a surface of the zinc selenide layer, or a highly reflective surface provided by another element.