Abstract: In a method for monitoring particulates in stacks or ducts a back-scatter monitor uses a solid-state laser to emit a collimated beam, the intensity of which is controlled via feedback from a reference detector. The beam is split so that part goes to a reference surface for calibration checks, and part is directed to pass at a selected angle through a gaseous sample. Optical energy scattered from particles in the sample is detected by viewing optics to provide an indication of particulate concentration. The beam steering mechanism can direct the optics to view scattering along a selectable axis that intersects the laser beam at a specified location within the gaseous sample. The method can be used to determine the opacity of the gaseous sample providing a basis for correlation to particulate loading of that portion of the particulates that are of a size comparable to the wavelength of light.

Abstract: An improved method of monitoring particulates in stacks or ducts utilizes transmissometer/particulate monitor of the type which has an optical assembly containing a solid state light source of visible light such as a light-emitting diode or a solid-state laser. The light source emits a collimated beam that is split, part of which is focused onto a reference detector that monitors the intensity of the light source, while the other part is directed to a beam-steering apparatus that causes the beam to accurately pass through a gaseous sample to a desired location such as a retro-reflector. A position-sensing detector is used in a closed-loop manner to control the beam-steering apparatus. The ratio of the total energy of the detected light beam, relative to the reference detector output, is used to determine the opacity of the gaseous sample for the purpose of providing a basis for correlation to particulate loading of that portion of the particulates that are of a size comparable to the wavelength of light.

Abstract: An improved transmissometer/particulate monitor of the type which has an optical assembly containing a solid state light source preferably a solid-state laser. The light source emits a collimated beam that is split, part of which is focused onto a reference detector that monitors the intensity of the light source, while the other part is directed to a beam-steering apparatus that causes the beam to accurately pass through a gaseous sample to a desired location such as a retro-reflector. A position-sensing detector is used in a closed-loop manner to control the beam-steering apparatus. The ratio of the total energy of the detected light beam, relative to the reference detector output, is used to determine the opacity of the gaseous sample or to provide a basis for correlation to particulate loading of the sample or both.

Abstract: A gas sampling system utilizes small sample vacuum transport to reduce the dew point of the sample. A vacuum pump maintains a substantial vacuum on the sampling system causing a sample, drawn at a rate less than a liter per minute, to be drawn and transported under partial vacuum for analysis. A dryer can be placed near the sampling probe to further reduce the dew point prior to the vacuum transport. The dew point of the sample is affected by both the dryer and the degree of vacuum transporting the gas mixture. As such, the dew point can be varied indefinitely by any reasonable combination of moisture removal by the dryer and vacuum pump strength.

Abstract: A method and apparatus for dynamic calibration of monitoring equipment of the type which uses a Type-S pitot tube connected to at least one transducer utilize a calibration air conduit having a distal end positioned opposite one opening of the Type-S pitot tube and a proximate end. A blower connected to the proximate end of the calibration air conduit blows air past the standard pitot tube and at least one opening of the type S pitot tube. A standard pitot tube placed in the calibration air conduit. Differential pressure readings are taken. There is a relationship between the differential pressure reading of the standard pitot tube and the differential pressure reading of the Type-S pitot tube which does not change unless the monitoring equipment of which the Type-S is a part leaks, is plugged or is otherwise operating improperly.

Abstract: A improved Type S or reverse type pitot tube has two conduit legs which are mirror images of one another. Each conduit leg has an input portion having a pressure port therein, a support portion and a connecting portion connected between the input portion and the support portion. The support portion and the connecting portion lie in one plane which plane is substantially perpendicular to a centerline through the input portions. The conduit legs are shaped and oriented relative to one another so that the pressure ports of the input portions of the first and second conduits are collinear and when placed in a conduit, the pitot tube will be symmetrical in a yaw plane and both symmetrical and non-interfering in a pitch plane. The first and second conduits are spaced apart over at least a portion of their length to define an opening adjacent the input portions which opening is at least 3 times wider and deeper than the input portions.

Abstract: An improved probe useful for measuring emissions of stack gases is equipped with a means for measuring moisture content and molecular weight of stack gases. A water feed tube is provided through the distal end of the probe and is fed water via a water feed line. An electrical temperature measuring device and water soaker device having spaced apart soaker feed holes is provided near the distal end of the water feed tube while a dry tubing encases the water feed tube below the temperature measuring device. A soaker wick encases part of the water feed tube and covers all of the temperature measuring device. Finally, an internal seal is provided between the dry tubing and the temperature measuring device to prevent thermally conductive heat from reaching the temperature measuring device. This structure enables the probe to make wet bulb-dry bulb measurements of stack gases.

Abstract: A method of measuring fluid flow through a conduit first finds a null position then rotates the probe 90.degree. from the null position to be aligned with the true flow direction of the field. The null position is found by incremental movement of the probe through selected angles. At each position a differential pressure reading is taken. These readings are then compared to determine subsequent incremental movements to identify an approximate null position. The true null position is found from the approximate null by applying at least squares fit to differential pressure readings taken within a range, preferably +/-5.degree., around the approximate null. The probe is then rotated 90.degree. from the null position. A plurality of differential pressure readings are taken and the square root of each such reading is found. An average of those square roots is multiplied by a predetermined constant to find the flow rate.

Abstract: A gas sampling system utilizing a pair of parallel sonic orifices. One of the orifices is connected to a source of filtered, heated samples. The second, larger orifice is connected to a source of dilution gas. A vacuum pump maintains a substantial vacuum behind the orifices, thus assuring critical flow therethrough. The sample and diffusion gas are mixed behind the orifices and transported under partial vacuum for analysis. The dew point of the sample is affected by both the ratio of the diameter of orifices and the degree of vacuum transporting the gas mixture. As such, the dew point can be varied indefinitely by any reasonable combination of orifice ratio and vacuum pump strength.

Abstract: A drive system for a probe of the type containing a first tubular housing within a second tubular housing which first tubular housing is advanced into and retracted from a conduit to take measurements of fluid within the conduit has a stepper motor for advancing the first tubular housing precisely controlled distances into and within the conduit. The stepper motor is connected to the first tubular housing through a friction drive roller which presses against the first tubular housing. Additionally, a rotational motor is connected to the outer tubular housing through a timing belt which extends around the second tubular housing. Sensors may be provided for measuring linear and rotational movement.

Abstract: A probe for measuring fluid velocity through a conduit has a pitot tube connected to a multiple channel cylindrical tube which is placed within a tubular housing. Drive motors are provided to permit precise rotation and longitudinal movement of the cylindrical tube and attached pitot tube in the conduit, typically a stack or duct. At least one differential pressure gauge is connected to the cylindrical. A computer directs movement of the cylindrical tube, receives differential pressure and static pressure readings from the differential pressure gauge and utilizes that data to calculate flow of the fluid through the conduit. The device is particularly useful for measuring stack gas flow which flow can be utilized to determine emissions of pollutants.

Abstract: A gas sampling system utilizing a pair of parallel sonic orifices. One of the orifices is connected to a source of filtered, heated samples. The second, larger orifice is connected to a source of dilution gas. A vacuum pump maintains a substantial vacuum behind the orifices, thus assuring critical flow therethrough. The sample and diffusion gas are mixed behind the orifices and transported under partial vacuum for analysis. The dew point of the sample is affected by both the ratio of the diameter of orifices and the degree of vacuum transporting the gas mixture. As such, the dew point can be varied indefinitely by any reasonable combination of orifice ratio and vacuum pump strength.