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Apparent Opening Size (AOS) Testers

Apparent Opening Size (AOS) Testers
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Geosynthetics and Geotextile Testing Equipment
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Apparent Opening Size (AOS) Testers

Apparent Opening Size Testers | ASTM D4751 Dry Sieving for Geotextiles

An apparent opening size tester measures the characteristic pore size of a geotextile by dry sieving graded glass beads through the fabric. The result, reported as O95, tells engineers the approximate largest soil particle a filter or separation fabric will pass. ASTM D4751 defines the method. Highway agencies, fabric producers, and commercial test labs rely on it when matching a geotextile to the soil it has to retain.

Qualitest supplies three configurations of the QualiGTX™ AOS series. All three run the same dry sieve procedure on single-layer geotextiles and related products. They differ in control type, batch capacity, and footprint.

Why Choose Qualitest for Your Apparent Opening Size Tester

Qualitest North America supplies testing and measurement equipment to laboratories, quality teams, and manufacturers, backed by responsive technical support and calibration service. The Apparent Opening Size Tester range is built for reliable, standards-driven results, so you can source confidently from a single partner. Our team helps you match the right configuration to your samples, applicable standards, and throughput, then supports you through installation and beyond.

Request a Quote

Tell us your fabric types, your monthly test volume, and the space you have available, and we will point you to the right apparent opening size tester. Contact the Qualitest team for pricing and lead times.

Applications

Opening size data drives fabric selection wherever a geotextile separates two materials while still passing water.

  • Highway and Airfield Construction: confirms that separation geotextiles keep subgrade fines out of base course aggregate under traffic loading.
  • Geotextile Manufacturing QC: verifies that finished rolls hold the O95 value printed on the product data sheet.
  • Drainage and Filter Design: supplies the opening size figure engineers compare against soil d85 when sizing a filter fabric.
  • Dams, Canals, and Levees: qualifies filter fabrics installed behind riprap, beneath revetments, and around toe drains.
  • Erosion and Sediment Control: screens silt fence, scour aprons, and slope stabilization fabrics before installation.
  • Landfill and Containment Systems: checks pore size on filtration and cushion layers in leachate collection and cover designs.
  • Independent Test Laboratories: covers routine AOS determinations for specifiers, agencies, and certification programs.

Apparent Opening Size Tester Range

Three models cover the range from occasional verification work to high-volume incoming inspection. Each uses a 200 mm sieve column with 400 mm stack height and a 0.37 kW drive.

ModelControlCapacity and AccessoriesSize and WeightBest Suited To
QualiGTX™ AOS TColor touchscreen5 specimens per cycle; 5 pressing rings and a graded glass bead set included; low-noise drive700 × 620 × 1360 mm, 160 kgLabs running steady incoming inspection volume that want guided operation and quieter running in shared space.
QualiGTX™ AOS MManual controls5 specimens per cycle; 5 pressing rings, 5 stainless steel sieve pans, and a graded glass bead set included770 × 650 × 1060 mm, 80 kgLabs that want five-specimen throughput and individually collected bead samples without a programmable interface.
QualiGTX™ AOS DSMMotorized shakerStandard sieve column configuration750 × 480 × 850 mm, 70 kgLabs with limited bench or floor space, or those running AOS tests occasionally alongside other geosynthetic work.

How to Choose the Right Apparent Opening Size Tester

  • For high test volume with several operators: choose the QualiGTX™ AOS T, where touchscreen control keeps the procedure consistent from shift to shift.
  • For five-specimen batches on a simpler machine: choose the QualiGTX™ AOS M, which pairs manual controls with stainless pans that keep each specimen's beads separate for individual weighing.
  • For a laboratory short on space: choose the QualiGTX™ AOS DSM, the smallest and lightest unit in the range at 70 kg.
  • For a shared office or sample-prep area: choose the QualiGTX™ AOS T, whose low-noise drive reduces the tapping noise typical of sieve shakers.
  • For occasional verification rather than routine QC: the QualiGTX™ AOS DSM covers the method at the lowest footprint and cost of ownership.
  • Before ordering: confirm your incoming power supply, since these units are specified at 380 V.

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Apparent Opening Size (AOS) Testers | Available Products

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Touch-screen Geotextile Apparent Opening Size (AOS) Tester

Touch-screen Geotextile Apparent Opening Size (AOS) Tester

Determine geotextile apparent opening size by dry sieving with a touch-screen AOS tester that runs five specimens at once. Request specs and pricing…
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Manual Geotextile Apparent Opening Size (AOS) Tester

Manual Geotextile Apparent Opening Size (AOS) Tester

Measure geotextile apparent opening size by dry sieving. Manual-control AOS tester runs five specimens per cycle with stainless pans. Request pricing…
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