Omniprobe - Aeroprobe Corporation

OmniprobeEngineeringFlow-MeasurementSolutions

Straight Omniprobemulti-hole probes). The introduction of the omniproberepresented a vast improvement with regards tothe angular resolution of multi-hole probes. By employing12 pressure ports distributed on the surfaceof a spherical surface, the omniprobe can accuratelymeasure flows from virtually any direction. Like thetraditional multi-hole probes, data acquisition withthe omniprobe requires (1) the probe itself, (2) anaccurate aerodynamic probe calibration, (3) pressuresensors and data acquisition in order to measure theprobe port pressures and (4) a pressure-to-velocityreduction method based on the calibration. Thisdocument gives product information for (1), (2) and(4) above.Omniprobe:Standard Omniprobe:Aeroprobe offers two standard omniprobegeometries: straight and L-shaped. Standardconstruction material is stainless steel.length and is stainless steel. The standard probes areshown in Figure 1. Geometrically similar probes areavailable with a tip diameter of 6.35 mm.All standard omniprobes are supplied with onecalibration at a requested speed. Additionalcalibrations at other speeds may be specified onorder. Custom omniprobes are normally suppliedwith a full calibration, unless this is precluded bygeometry restrictions.The advantage of using an omniprobe rather than atraditional five- or seven-hole probe is the angularresolution capability. Seven-hole probes are highlyaccurate until the velocity vector reaches a totalangle of about 70° with respect to the flow. For fiveholeprobes this angle is about 60°. Omniprobes areable to resolve velocity vectors having angles of upto 165° with the probe axis (relative to base-to-tipdirection). This allows the omniprobe to measureflows with very high angularity and even reversedflows.Standard omniprobes have a 9.53 mm tip diameter,and a 152.4 mm overall length. The hex mount is9.53 mm flat-to-flat. The exit tubing for pressureconnections is 1.07 mm in diameter, 44.5 mm inOmniprobe

www.aeroprobe.comFigure 1(a): Standard Straight Omniprobes. All Dimensions in Millimeters.

Figure 1(b): Standard L-Shaped Omniprobe. All Dimensions in MillimetersOmniprobe

LStraightDL"L" ShapedTDFigure 2: Probe Design and Specificationwww.aeroprobe.com

Table 1: Probe Design and SpecificationGeometry Codes Probe Type Tip GeometryD Tip Diameter S Straight S SphericalL Overall Length L L-ShapedTProbe Tip LengthOmniprobe Model Number DefinitionP or CPProbe TypeP = Standard ProbeCP = Custom ProbeStraight or L-ShapedSee Codes AboveH Number of Probe Ports = 12 or 18-Tip GeometryD-L-TSpherical = STip Diameter in Hundredths of a Millimeter (Three Digits)Overall Length of Probe in Millimeters (Three Digits)Length of Probe Tip in Millimeters (Three Digits)Note: T is used only if Required, Omitted OtherwiseOmniprobe

Omniprobe CalibrationsThe probe calibration is essential to proper operationof the probe. It defines a relationship between themeasured probe port pressures and the actual velocityvector.The omniprobe calibration process consists ofplacing the probe in a uniform, known flowfield(known in terms of velocity magnitude and direction,density, temperature, static pressure), and thenrotating the omniprobe to over 7000 differentorientations with respect to the known velocityvector. The probe tip is maintained at the samephysical location during the entire calibrationprocess. At each orientation, the probe portpressures, the freestream dynamic pressure and thestagnation thermodynamic quantities are recorded.In this way, a calibration map that relates portpressures to velocity can be created. One map iscreated for each Mach/Reynolds number.Omnipro Pressure-to-Velocity ReductionSoftwareThe omniprobe pressure-to-velocity reductionsoftware package is a post-processing, Windowscompatiblepackage. A window from the program isshown in Figure 3.The software utilizes a local-least squares (LLS)fit of the closest (to the test point in question)calibration points, for each of the calibrationvariables. The LLS searching algorithm usesspecialized multi-region search routines to improveaccuracy.The reduction algorithm has typical average errors of1% (or less) in the velocity magnitude and 0.5° (orless) in the flow angles, when used with calibrationdata generated in our facilities.For more information about aerodynamiccalibration facilities and instrumentation, pleasesee the conventional Aeroprobe brochure. Typicalcalibration speed ranges for the Omniprobe are givenin Table 4 as a function of omniprobe tip diameter.Note that calibrations at speeds in excess of 70 m/srequire the 6.35mm tip option, because of restrictionson the cross-sectional area of flow in our high-speedcalibration facility.Re-Calibration Interval:The Omniprobes are designed to maintain theaerodynamic calibration for long periods, as long asthe probe tip is not damaged or scratched and the tipgeometry of the probe is not altered. Under normaloperation and storage, the recommended calibrationinterval is 18-24 months.Figure 3: Omniprobe Pressure-to-VelocityReduction Software Screen CaptureTable 5: Standard Calibration Speed Ranges forTypical Omniprobe Tip DiametersOmniprobe TipDiameter (mm)Calibration VelocityRange6.35 5 to 320 m/s9.53 5 to 70 m/sOmniprobe

Ordering InformationItemPS12PL12PS12-HT900TIP-OMNI6SPCOXC0DescriptionStandard OmniprobesStandard Straight 12-holeOmniprobe, CalibratedStandard L-Shaped 12-holeOmniprobe, CalibratedStraight High-TemperatureOmniprobe, 9.53 mm Tip OD,Rated to 900°CStandard Omniprobe TipOptions6.35 mm Tip DiameterOmniprobe CalibrationsStandard Setup and Calibrationof Omniprobe (Specify Speed)Extra OmniprobeCalibration (Specify Speed)RequirementsUse of omniprobes requires ability to measure portpressures. Aeroprobe provides complete pressuredata acquisition systems and software for thispurpose (sold separately). The Omnipro softwarerequires Windows OS.Notes:• Standard Omniprobes Are Shown in Figure 1,All Other Geometries Must Be Given a CustomDesignation.• All Standard Probes Include One StandardCalibration at a Speed of the Customer’s Choice(5 m/s - 320 m/s for 6.35 mm Tips, and 5 m/s- 60 m/s for 9.53 mm Tips). Specify Speed onOrder!• Custom Omniprobes Include One StandardCalibration at a Speed of the Customer’s Choiceif Omniprobe Geometry PermitsCPS12CPL12ETUB-3-1RPRP-OMNI-BRPRP-OMNI-ESW-OMNICustom OmniprobesCustom Straight 12-holeOmniprobe, CalibratedCustom L-Shaped 12-holeOmniprobe, CalibratedTubingFlexible Tubing for ProbePneumatics, 1/32" ID, 3/32"OD, 50 ftRepairProbe Repair, BaseProbe Repair, ExtendedPressure-to-VelocityReduction SoftwareOmnipro Reduction SoftwareFigure 4: 9.53mm Omniprobe TipAdditional InformationFor information about other Aeroprobe products,please visit our website: www.aeroprobe.com.www.aeroprobe.com

Aeroprobe Mission:Design, develop, manufacture, and deliver 21 st -century technology air/liquid flow measurementprobes characterized by miniaturization, high accuracy & fast response.More About Aeroprobe:A Virginia Tech spin-off, Aeroprobe Corporation is located in the VT Corporate Research Center. Maintainingclose ties with VT enables Aeroprobe to perform basic and applied research aimed at advancing probetechnology.Aeroprobe works closely with manufacturing partner Schultz-Creehan to design, test, and produce highquality,custom-built measurement devices and equipment employing modular lean-manufacturing methods.Schultz-Creehan has unique mechanical and electronic design, test, and simulation capabilities, which areapplied to meet specific customer needs.AeroprobeCustomers:• GE R&D• NASA LaRC• NASA Ames• GIE-SAA• BMW• Williams• Sandia NationalLaboratory• Honda R&D• Techsburg• GE AircraftEngines• Hill AFB• Virginia Tech• University ofCentral FloridaInternational Business:With distributors in 20 countries and approximately 50%of sales outside the USA, Aeroprobe is an internationallyrecognized name.We have distributors in the following countries:ArgentinaAustraliaAustriaBelgiumBrazilCzech RepublicFinlandFranceGermanyIndiaItalyJapanKoreaMexicoNetherlandsNorwayPortugalSingaporeSlovakiaSpainSwedenSwitzerlandTurkeyU.K.Aeroprobe Corporation1700 Kraft Dr.Suite 2350Blacksburg, VA 24060Ph: (540) 951-3858Fax: (540) 951-8618info@aeroprobe.comwww.aeroprobe.com