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Different Weight, Moisture, and Thickness Sensor Technology for Web Applications

August 3, 2020

Web gauging systems are the key to meeting tight customer specs while also reducing waste and the overall expense associated with a production line. Which sensor technology to use depends on the substrate being measured as gauges are used to measure everything from the adhesive applied to tape to roofing products to soup bowls. Use this guide to help understand some of the technology that is available and let a Quad Plus expert help you find the right one for your production line.

Beta Transmission (Sr-90 and Kr-85)

This type of sensor in a web gauging system works by measuring the ratio of the number of beta particles that pass through the material to the number without any material. Beta transmission sensors provide accurate measurements and control for film and sheet extrusion, extrusion coating, nonwovens, calendering, and roofing products. Here are some examples:

  • Plastic Film Production: cast film lines, co-extruded film lines, Biax film lines (BOPP, BOPET, BOPA), stretch film lines, and shrink film lines.
  • Cast Sheet Lines: white goods industry, HIPS sheet extrusion, and ABS extrusion.
  • Vinyl Calendered Sheet Lines: PVB sheet extrusion.
  • Nonwoven Production: spunlace, spunbound, airlaid, wetlaid, carded, and melt-blown.
  • Paper Production: tissue paper, paper mills (fine paper, fluting/testliner, greyboard, duplex board, filter paper, MG paper, and cement sack paper).
  • Coating Processes: extrusion coating lines, blade coating lines, roll coating lines, tandem Extrusion coating lines, lamination lines, saturation coating lines, and slot die coating lines.
  • Converting Plants: PE film thicknesses on liquid packaging production line, adhesive weight on PP Film, adhesive weight measurement on silicone coated release paper for label stock, wax coat weight on paper, PVC coat weight on paper, PE film coating on aluminum foil, coat weight on duplex board, thickness of flooring, and coat weight on carbonless copy paper.
  • Tire Production: rubber calenders, gum calenders, steel core calender, and textile core calender.
  • Roofing/Building Material Production: TPO sheet extrusion, PVC membrane extrusion, geotextile membrane extrusion, medium and heavy foams, asphalt shingles, roll asphalt roofing, and insulation.


A Terahertz web gauging system is a safe, non-nuclear thickness sensor solution for both single and multi-layer applications. This system is capable of providing simultaneous measurements of thickness, basis weight, and density of a product. It can also provide multi-layer measurements of products without specific calibration and direct thickness measurements without being sensitive to color or additives. Some examples of products this system would be a good fit for include TPO/PVC roofing, asphalt roofing, plastic pipe production, and metal pipe coating.

Near-Infrared Reflection

Near-infrared reflection is used by a variety of industries to measure moisture content and other product variables. Because this web gauging system is fast, accurate, and straightforward, the technology is used in the quality control of everything from food and beverage manufacture to adhesive coatings. Here are a few examples of where you might find near infra-red reflection gauging systems:

  • Paper Production (Moisture Percentage): Tissue Paper.
  • Nonwoven Production (Moisture Percentage): spunlace, spunbond, airlaid, wetlaid, hybrid, carded, and melt-blown.
  • Converting: adhesive weight on PP film, adhesive weight on silicone coated release paper for label stock, moisture on paper after lamination with aluminum foil, wax coat weight on paper, coat weight on duplex board, moisture of decorative paper, coat weight on carbonless copy paper, and coat weight and moisture on thermal paper.

X-Ray Transmission

X-ray transmission web gauging systems provide weight and continuous thickness measurements of web products. You’ll find four common types of x-ray transmission measurement systems in a variety of applications:

  • Low Energy (Soft) X-Ray Transmission: plastic film production (cast film lines, co-extruder film lines, Biax film fines such as BOPP and BOPET, stretch film lines, and shrink film lines) and in paper mills to measure ash percentage (fine paper, fluting/testliner, greyboard, duplex board, filter paper, MG paper, and cement sack paper).
  • High Energy (Hard) X-Ray Transmission: engineered wood products such as medium-density fiberboard (MDF), particleboard (LDF), oriented strand board (OSB), cross-laminated timber (CLT), parallel strand lumber (PSL), laminated pressboard lines, and plywood Lines. Plus building material production (glass wool, polyiso foam board, gypsum board, and polystyrene foam board)
  • X-Ray Fluorescence Sensor: hot-dip galvanizing and electro-galvanizing.
  • C-Frame X-Ray: steel plants (hot roll mill, cold roll mill, slitting line, and tension leveling line), aluminum plants (continuous caster, hot rolling mill, cold rolling mill, foil mill, slitting line, and tension leveling line.

The Right Web Gauging System for You

Our team of technology specialists has the right combination of machine and process knowledge to recommend the best configuration for your web gauging system for your operation. We provide full turnkey solutions and will stay with your project from planning and installation to training and after-installation support. When you’re ready to partner with a team that’s dedicated to giving exceptional results and peace of mind, it’s time to call the experts at Quad Plus.