Abstract: A method and apparatus for automatically detecting a coherent frequency burst is disclosed. The apparatus 10 determines the approximate frequency and duration of the burst. The apparatus 10 operates utilizing principles of autocorrelation to reject random noise and maximize the efficiency of a down stream data signal processor. The apparatus 10 includes delay means 30 which accepts a digitized signal from a device, such as a photodetector in an LDV, and generates a plurality of delayed signals. The delayed signals are then multiplied by the original signals by multiplier means 40. The multiplied signals are provided to averaging circuits 50. The averaged signals are then compared to a reference level by comparators 60, the output of which is provided to priority encoder 70. Priority encoder 70 prioritizes the signals received from comparators 60 and determines the length of the burst.

Abstract: Methods and apparatus for enhancing the accuracy of laser optical measuring instruments using fringe pattern spacing are disclosed. The apparatus in one embodiment includes a laser beam source 10, a beam splitter 14, and mirrors 22 to deflect the beams 18, 20 emitted from the beam splitter 14 to a sensing volume. Alternative embodiments include prisms 42, 44, gratings 62 or other optical devices in lieu of mirrors 22. Objects passing through the sensing volume scatter light which is detected by the instrument to determine, among other things, the velocity of the object. The emitted beams 18, 20 are automatically deflected in response to wavelength changes of the laser beam 16 such that variations in the fringe spacing, due to variations in laser beam 16 wavelength, are compensated by variations in the closing angle K of the emitted, deflected beams. The fringe pattern spacing is thereby held more nearly constant enhancing the accuracy of the instrument.

Abstract: An optical fiber connector assembly for coupling an optical fiber cable having optical fibers to an instrument equipped with a light source and a photodetector. The connector assembly has a housing accommodating a pair of ferrules that support the optical fibers. The ferrules have cone-shaped heads and generally flat forward ends. The optical fibers have ends that are flush with the flat ends of the heads. The heads of the ferrules seat into cone-shaped reccesses in receptacles mounted on the instrument. The light source and photodetector are aligned with the receptacles so that the light from the light source is transmitted to a first optical fiber and the light from second optical fibers is received by the photodetector. A screw mounted on the housing is threaded into a hole in the instrument to releasably connect the housing to the instrument and locate the heads in alignment with the cone-shaped recesses in the receptacles.

Abstract: A Doppler velocimeter having laser generating crossing light beams provides a crossing and focus area forming a measuring volume having regions of high and low light intensity. Solid or liquid particles moving through the measuring volume scatter light which is sensed and converted into a signal having a frequency. A signal processor measures the frequency by detecting and tracking an individual zero crossing of a particle through the measuring volume to provide real time information about the coherent component of the signal. This information is useable to determine the velocity of the particle moving through the measuring volume.

Abstract: A condensation nucleus counter (1) for measuring particulate concentration within a gaseous environment, including an inlet orifice (3) leading to a flow path (5) within saturator (4). The resultant vapor (10) enters a condenser section (11) wherein the particulate matter suspended within serves as the nucleus for condensation. The enlarged droplets (23) thus formed enter a conventional optical particle counter section (15).

Abstract: A pressure differential measuring apparatus (25) wherein the direction of fluid flow (5) is determined by calculating the ratio between pressures of two discrete fluid masses (3, 4). The device includes two tandem thermal sensors (7, 6), the upstream sensor creating a thermal wake which is carried past the downstream sensor, thereby slowing the downstream sensor's nominal cooling rate. A venturi (8) is utilized to create desired flow characteristics in the region of the sensors.

Abstract: An optical fiber connector assembly for coupling an optical fiber cable having optical fibers to an instrument equipped with a light source and a photodetector. The connector assembly has a housing accommodating a pair of ferrules that support the optical fibers. The ferrules have cone-shaped heads and generally flat forward ends. The optical fibers have ends that are flush with the flat ends of the heads. The heads of the ferrules seat into cone-shaped recesses in receptacles mounted on the instrument. The light source and photodetector are aligned with the receptacles so that the light from the light source is transmitted to a first optical fiber and the light from second optical fibers is received by the photodetector. A screw mounted on the housing is threaded into a hole in the instrument to releasably connect the housing to the instrument and locate the heads in alignment with the cone-shaped recesses in the receptacles.

Abstract: An improved bridge-type hot-wire constant overheat anemometer having current controlled temperature compensation circuitry, whereby matched sensors may be employed. Independent voltage sensing and current supply paths along with high impedance cross-coupled velocity sensing circuitry assures device accuracy.

Abstract: A constant temperature anemometer having an enhanced frequency response. A sensor element is included within one leg of a bridge circuit with a feedback circuit being operatively connected to the bridge circuit. The bridge circuit frequency response is shaped by impedance elements connected in parallel with another leg of the bridge circuit. In a preferred embodiment, the impedance elements include serially connected resistance and capacitance elements.

Abstract: A fluid movement measuring apparatus having ion collecting electrical conductors spaced from an ion generating source located within a housing. The housing has one or more circumferential rows of openings in communication with the space or fluid flow path between the ion generating source and ion collecting conductors. Ions migrating across the space are deflected by moving fluid in the direction of the fluid flow. Electrical currents caused by ions collected on one or more electrical conductors are directed to differential amplifiers. The differential amplifiers provide output voltages that are proportional to the differences in current collected by opposed electrical conductors. These output voltages provide information as to the movement, such as velocity and direction, of the fluid flowing in the fluid flow path.

Abstract: A fluid movement measuring apparatus having ion collecting electrical conductors spaced from an ion generating source located within a housing. The housing has one or more circumferential rows of openings in communication with the space or fluid flow path between the ion generating source and ion collecting conductors. Ions migrating across the space are deflected by moving fluid in the direction of the fluid flow. Electrical currents caused by ions collected on the separate electrical conductors are directed to differential amplifiers. The differential amplifiers provide output voltages that are proportional to the differences in current collected by opposed electrical conductors. These output voltages provide information as to the movement, such as velocity and direction, of the fluid flowing in the fluid flow path.

Abstract: A particle size measuring apparatus and method has a laser unit and optics that provide a central focused light area surrounded by an annular focused light area. Particles moving with fluid through the center of central focus light area cause the light to scatter. The scattered light is sensed and converted to readable signals indicative of particle size.

Abstract: A fluid movement measuring apparatus having ion collecting electrical conductors spaced from an ion generating source. Ions migrating across the space are deflected by moving fluid in the direction of the fluid flow. Electrical currents caused by ions collected on the separate electrical conductors are directed to differential amplifiers. The differential amplifiers provide output voltages that are proportional to the differences in current collected by opposed electrical conductors. These output voltages provide information as to the movement, such as velocity and direction, of the fluid flowing in the fluid flow path.

Abstract: A diagnostic apparatus and method for measuring motion of flowing solid and fluid particles that utilizes a differential doppler system and makes measurements parallel to the optical axis of the system. The system includes a laser generating a light beam directed toward a light beam splitter. The splitter separates the light beams into a plurality of beams that are focused in a crossing and focusing area. Receiving optics aligned with a photodetector sense light scattered by particles moving in the focusing area. The photodetector converts the light signals to electrical signals. A signal mixer coupled to the photodetectors operates to produce a difference electrical signal established by the difference between the frequencies of the electrical signals produced by the photodetector. The difference electrical signal is converted with signal processors to a voltage proportional to the velocity of particles moving through the focusing area.