Abstract: A chemical detection system performs controlled exposures to diagnose the pneumatic components and chemical sensors prior to measuring a chemical emission. A control module provides the system control and data processing to perform the diagnosis. The control module manipulates an emission sample retrieval system to provide precise exposure during the diagnostic routines. A sensor interface circuit interrogates the chemical sensors and stores the data for analysis. The chemical sensor exhibits predictable changes in response during predetermined exposure scenarios. By utilizing numerous time domain signal processing techniques, both system and sensor level fault conditions are determined.

Abstract: A sensor circuit for use in measuring concentrations of an analyte in a fluid is comprised of a BAW sensor, a voltage variable capacitor connected to the sensor, an input which supplies a bias warping dc voltage to the voltage variable capacitor, and a resonant oscillator circuit. The resonant oscillator circuit detects the fundamental frequency of the sensor and produces a resonant signal frequency. The bias warping dc voltage applied to the voltage variable capacitor warps the resonant frequency of the circuit away from inharmonic noise.

Abstract: A chemical detection system performs controlled exposures to diagnose the pneumatic components and chemical sensors prior to measuring a chemical emission. A control module provides the system control and data processing to perform the diagnosis. The control module manipulates an emission sample retrieval system to provide precise exposure during the diagnostic routines. A sensor interface circuit interrogates the chemical sensors and stores the data for analysis. The chemical sensor exhibits predictable changes in response during predetermined exposure scenarios. By utilizing numerous time domain signal processing techniques, both system and sensor level fault conditions are determined.

Abstract: A magnet assembly is disclosed for use with a magnetic flux sensor to provide a position sensor adapted to detect a position of a moveable member. The magnet assembly comprises a magnet housing defining an inner surface. A magnet is provided that is sized for insertion into the magnet housing and adapted for movement with the moveable member, the magnet having a north pole and a south pole, wherein the magnet generates a magnetic flux. A centering ring is positioned between the magnet and the magnet housing, the centering ring including a biased wall acting to center the magnet in the magnet housing.

Abstract: A displacement sensor includes a magnet assembly having a housing for mounting to one of first and second relatively moveable elements. A magnet assembly is mounted to one element and defines a longitudinal space having an axis along its length. The magnet assembly includes at least one magnet having a north and a south pole that supply fringing magnetic flux in the longitudinal space and a flux-shaping pole piece on each of the north and south poles. A magnetic field sensor assembly has a housing for mounting to the other of the first and second elements for movement along an axis in the space parallel to the magnet assembly. In one embodiment, each of the flux-shaping pole pieces has a pentagon shape in a plane of primary flux pattern, forming a first face confronting the longitudinal space between the first and second magnets.

Abstract: A calibration system includes an acoustic wave gas sensor array, and a delivery device adapted to eject a measured quantity of a liquid calibrant to the gas sensor array. The delivery device includes a connector adapted for connection to an air supply source, a reservoir adapted to store a supply of the liquid material, an outlet arranged for placement adjacent to the gas sensor array, a dosing chamber sized to define and store a measured quantity of the calibrant, a conduit disposed between the dosing chamber and the reservoir and arranged to provide flow communication therebetween, a portion of the conduit arranged to be responsive to a pressure gradient within the dosing chamber over a predetermined time interval to thereby prevent flow from the dosing chamber toward the reservoir during the predetermined time period, and a valve mechanism adapted to apply the pressure gradient to the dosing chamber over the predetermined time interval.

Abstract: A magnet assembly is disclosed for use with a magnetic flux sensor to provide a position sensor adapted to detect a position of a moveable member. The magnet assembly comprises a magnet housing defining an inner surface. A magnet is provided that is sized for insertion into the magnet housing and adapted for movement with the moveable member, the magnet having a north pole and a south pole, wherein the magnet generates a magnetic flux. A centering ring is positioned between the magnet and the magnet housing, the centering ring including a biased wall acting to center the magnet in the magnet housing.

Abstract: The concentration of an analyte in a fluid is measured by a quartz crystal microbalance sensor device in the fluid containing a concentration of the analyte. The sensor device exhibits a resonant frequency representative of the concentration of the analyte in the fluid. A quartz crystal microbalance reference device has a resonant frequency lower, by a predetermined amount, than the initial resonant frequency of the sensor device before the sensor device is exposed to the analyte. A signal is derived based on the difference of the resonant frequencies of the sensor and the reference device, and a first counter counts a predetermined number of cycles of the difference signal frequency to derive a sample time period. A second counter counts cycles of a clock signal frequency during the sample time period to derive a count representative of the difference signal frequency.

Abstract: An electrical circuit and method for measuring small variations in a high frequency signal is disclosed. The circuit generates a coarse measurement of the input signal frequency and a reference signal having the same frequency as the frequency represented by the coarse measurement. The circuit measures the difference in frequency between the input signal and the reference signal, and adds the coarse measurement and the difference measurement to determine the frequency of the input signal. The circuit may be used in conjunction with a piezoelectric acoustic wave device and oscillator to provide an apparatus for accurately measuring low concentrations of a gas.

Abstract: A method and apparatus for collecting fugitive emissions from valves and other emissions sources is disclosed. The apparatus comprises a capsule enclosing at least a portion of the equipment and an ejector in fluid flow communication with the capsule. The ejector is connected to a compressed air source, which creates a pressure drop in the ejector which draws emissions from the capsule into the ejector. The apparatus may include a sensor chamber housing gas sensors to detect the presence and concentration of any emissions from the equipment being monitored, and may store emissions data, communicate the data to a plant process control system, and use the data to control plant conditions to reduce or eliminate the emissions.