Yokogawa Releases WG51S2 Infrared Sensor for the WEBFREX NV Online Thickness Gauge

Tokyo, Japan - August 14, 2018

Yokogawa Electric Corporation (TOKYO: 6841) announces that it has developed the WG51S2 infrared sensor for the WEBFREX NV online thickness gauge. Positioned as an OpreX™ Quality Control System family solution, the WG51S2 infrared sensor enables the WEBFREX NV online thickness gauge to measure and control the thickness of films and sheets with greater accuracy than ever before. This new product will be released on September 3.

WG51S2 infrared sensor for the WEBFREX NV online thickness gauge
WG51S2 infrared sensor for the WEBFREX NV online thickness gauge

Development Background

Thickness gauges are used on film and sheet production lines to measure and control film and sheet thickness. They ensure that all products coming off the line are of uniform thickness. Various kinds of plastic film have been developed for packaging, including highly functional film that can preserve the quality of packaged contents and film that can be printed with vivid colors to improve the attractiveness of the packaging. Environmental concerns have driven efforts to make plastic films recyclable and thinner, and so it is important to have thickness gauges that are capable of measuring the thickness of thin films with a high degree of accuracy. To satisfy this need, Yokogawa has developed this infrared sensor.

For the handling of various kinds of films and sheets, four different types of noncontact sensors are available for use with the WEBFREX NV online thickness gauge. These are a β-ray sensor that can measure a wide range of materials, an X-ray sensor that is suitable for measuring compositionally homogeneous films, an infrared sensor that is suitable for use with plastic films that absorb infrared light, and an optical sensor that is suitable for measuring multilayer films and other kinds of transparent films.


  1. Maximum accuracy of ±0.1㎛
    With its unique optical system consisting of a frequency-modulated light source*1 and dual-integrating spheres*2 and its digital lock-in amplifier*3 circuit for weak-signal detection, the WG51S2 offers significantly improved accuracy and measurement stability. It is particularly suitable for use with thin films (10 to 300㎛), with repeatability within ±0.2㎛ . With 20㎛ thick polypropylene film, the sensor achieves its maximum accuracy of ±0.1㎛. It can be used for a variety of applications including transparent, opaque, and foamed films. As the WG51S2 has been optimized for reliable on-line measurement, it is much less affected by film pass-line fluctuation*4 and/or disturbance infrared light*5, and precise measurement is assured even with fast moving film.
  2. Designed for maintainability and compatibility
    Conventional sensors are equipped with a motor for rotating the filter, and the motor needs to be replaced periodically. The WG51S2 uses a frequency-modulated light source with no consumable mechanical parts. The light source is the only part that needs to be periodically replaced, and it is designed for easy replacement and requires no adjustments.
    With already installed WEBFREX NV systems, upgrades to the new WG51S2 sensor can be done without having to change the frame that houses the sensor. For existing WEBFREX3 systems, it is also possible to upgrade to the WG51S2 sensor without changing the frame if one first performs a partial system upgrade to the WEBFREX NV.

*1 Infrared light at different wavelengths is modulated to specific frequencies for simultaneous irradiation of a target film.

*2 An optical system with a pair of spheres that are positioned on opposing sides of a target film. Irradiated infrared light is reflected back and forth between the inner surfaces of the spheres, passing repeatedly through the target film.

*3 A high performance digital technology for the recovery of signals in noisy environments. Through the use of multiple demodulators, signals with different frequencies can be simultaneously processed.

*4 Changes in the height of the film as it is transported that result in measurement error. This can be caused by the drive system, creasing of the film, or curling of the film at its edges.

*5 Thermal radiation from a target film that is being processed at high temperature and/or ambient infrared light that causes sensor measurement errors

Major Target Markets

Manufacturers of separators used in rechargeable batteries and plastic film used in product packaging


Measurement and control of film and sheet thickness to ensure product quality

About Yokogawa's Online Thickness Gauge Business

In 1963, Yokogawa entered the thickness gauge business by releasing a β-ray gauge for measuring the thickness of paper. In 1972, the company released the B/M1000, a thickness gauge with a built-in computer. To cover a wider range of film products, Yokogawa came out with the 8640 radiation-type thickness gauge in 1974. The company has continued to develop sophisticated technologies for the measurement and control of thickness, and currently offers measurement and control system for paper and coating machines and the WEBFREX NV online thickness gauges for the measurement and control of plastic, resin, and metal sheet thickness. With its best-in-class resolution and scanning speed, Yokogawa's WEBFREX NV is Japan's top-selling online thickness gauge, and it has also captured a significant share of markets outside Japan (based on a July 2018 Yokogawa market survey).

About OpreX

OpreX is the comprehensive brand for Yokogawa's industrial automation (IA) and control business. The OpreX name stands for excellence in the technologies and solutions that Yokogawa cultivates through the co-creation of value with its customers, and encompasses the entire range of Yokogawa's IA products, services, and solutions. This brand comprises the following five categories: OpreX Transformation, OpreX Control, OpreX Measurement, OpreX Execution, and OpreX Lifecycle. One of the product groups that make up the OpreX Control category is the Quality Control System family, which includes WEBFREX NV. With its various OpreX Control solutions, Yokogawa is able to quickly effect changes for its customers that lead to a transformation in such areas as management and operations, and provides highly reliable control technology that ensures high efficiency, high quality, and safe and stable plant operations.

With the OpreX brand, Yokogawa will deliver integrated solutions that address specific needs and support its customers in their efforts to transform and grow their businesses.


About Yokogawa

Founded in 1915, Yokogawa engages in broad-ranging activities in the areas of measurement, control, and information. The industrial automation business provides vital products, services, and solutions to a diverse range of process industries including oil, chemicals, natural gas, power, iron and steel, and pulp and paper. With the life innovation business the company aims to radically improve productivity across the pharmaceutical and food industry value chains. The test & measurement, aviation, and other businesses continue to provide essential instruments and equipment with industry-leading precision and reliability. Yokogawa co-innovates with its customers through a global network of 113 companies spanning 61 countries, generating US$3.8 billion in sales in FY2017. For more information, please visit www.yokogawa.com.

The names of corporations, organizations, and products herein are either trademarks or registered trademarks of their respective holders.

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