Ultrasonic Wall Thickness Measurement

The LaserLinc UltraGauge+™ series of ultrasonic meters and gauges measure wall thickness, layer thickness, and concentricity of plastic, rubber, glass, and metal products. Typical applications include tubing, hose, pipe, insulated wire, cable, and certain multi-layer products.

When combined with a laser micrometer for outside diameter measurement, LaserLinc’s UltraGauge+ devices also provide an inside diameter (ID) measurement for tube, hose, and pipe.

UltraGauge+ meters are commonly installed on an extrusion production line for continuous in-process measurement. With precise real-time wall and concentricity measurement, operators can adjust extrusion die bolts to achieve concentricity within minutes after startup.

We make it easy to measure your high-specification products, leading to increased production yield. This ability provides a variety of benefits, including:

• Shorter startup cycles
• Reduced material usage
• Improved product quality
• Reduced costs

Thin Wall Measurement

One of the greatest benefits of LaserLinc’s UltraGauge+ technology is its thin-wall measurement capability. The device has been used to measure 0.001-inch [25 μm] wall thickness of micro polymer medical tubing and 0.003-inch [75μm] wall thickness of metal nickel titanium (NiTi / Nitinol) stent tubing.

LaserLinc’s UltraGauge+ product line includes a wide range of sensor assemblies and accessories to support a variety of production processes and locations.

LaserLinc’s line of UltraGauge+™ sensor assemblies provide continuous wall thickness measurement for round products such as medical tubing, insulated wire and cable, hose, pipe, and metal and glass tubing.

LaserLinc’s standard UltraGauge+ sensor assemblies typically include 4 or 8 transducers and are arranged in a circular pattern. They are available in a variety of standard configurations, or we can manufacture custom configurations for particular application requirements.

To optimize consistent and precise wall thickness measurement, transducers must be aligned with the product being measured. Typical LaserLinc fixtures include linear adjustments in vertical and horizontal axes. With adjustable fixtures, the ultrasonic sensor assembly can be moved to the product location rather than altering the path of the product and potentially affecting its shape or dimensions.

Our ultrasonic sensor assemblies:

• Measure a range of wall thicknesses by configuring with selected transducer frequencies
• Ensure accurate transducer-product alignment, reducing errors
• Eliminate/purge air bubbles for reliable, continuous operation
• Are simple to install and use, which saves operators time

Accessories and Custom Sensor Assemblies

If the product to be measured does not maintain stable positioning in the production process, various roller and cone guide accessories are available to stabilize the product for consistent measurement.

Ultrasound is a pressure wave with a frequency higher than the upper limit of human hearing (approximately 20 kHz). LaserLinc uses ultrasonic frequencies from 2.25 MHz to 50 MHz.

For measuring material thickness, the process involves the following:

• A pulse of electrical energy excites a piezoelectric transducer  
• The transducer converts the electrical energy into mechanical energy in the form of a sound wave
• The sound wave travels through a coupling medium (typically water) until it encounters a material with a different acoustic impedance (resistance to displacement by sound)

• At an acoustic interface, some sound energy is reflected—an echo is generated—and a portion of the energy continues onward into the next material

• An echo is generated at each acoustic interface so with a single-layer plastic tube immersed in water, two echoes occur:
  • One at the acoustic interface between water and the plastic
  • Another at the acoustic interface between plastic and air on the inside of the tube
• Each echo received by the transducer is converted back to electrical energy
• The electrical signal generated while the transducer is “listening” for echoes is analyzed by a digital signal processor (DSP) to measure the precise time between consecutive echoes
• The time between consecutive echoes is converted to a thickness measurement by multiplying by the speed of sound through the material, and dividing by two (since the sound must travel through the material and back to the transducer)