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Gloss measurements

Gloss is a measure of the optical reflectance of the paper surface. Since gloss is important for visual impact and is a significant component of paper printability, it is an essential measurement parameter for the producers of fine and coated grades, super-calendered, publication grades and coated boards.

The Gloss Measurement GL4265 uses a proven measurement technique, correlated to TAPPI standards, to accurately determine sheet gloss. It is the first sensor to thoroughly address key areas affecting on-line gloss measurement, such as standardization and passline sensitivity.

The GL4265 is an optical-based device which provides accurate measurements in a continuous, on-line scanning mode. The sensor utilizes a measurement principle which simulates the human eye’s perception of gloss and is in accordance with TAPPI standards.

The GL4265 features non-contacting, air-bearing sheet guides which stabilize the paper as it passes through the sensor package. Glass windows protect the optical components in the sensor housing from dirt, dust, moisture and other contaminants. To ensure ambient light insensitivity, the sensor features a totally enclosed measurement head and a high-intensity light source.

Light rays emitted by the sensor’s compact, halogen lamp are directed to a partially reflective mirror or “beam splitter”. This mirror directs 65 percent of the light toward the sheet at the TAPPI-specified incident angle of 75 degrees.

A lens collects the light that is reflected from the paper sheet near the angle of mirror reflection, or specular angle. The collected rays of light are focused onto the sensor’s photo-sensitive detector, where the gloss measurement signal is generated. The remainder of the light (35 percent) passes through the beam splitter and is reflected from a first-surface mirror directly toward the sensor’s detector. This light beam is utilized as a reference to standardize the sensor’s measurements. This standardization, which is accomplished optically without the use of moving parts, ensures that the gloss sensor is insensitive to temperature, dirt build-up on the measurement windows and aging of the source or detector components.

The GL4265 can be mounted above or below the sheet to provide a top or bottom measurement of sheet gloss. If desired, two sensors can be utilized for dual-sided gloss measurement. Gloss is expressed directly in gloss units (G.U.) with a black-glass standard having a value of 100 G.U.

Features

  • Measurement and standardization accomplished with no moving parts
  • Correlates with TAPPI Standard 480 om-85 measurement and geometry
  • Compact, totally enclosed measurement head ensures long-term reliability
  • High-intensity, halogen lamp eliminates ambient light sensitivity
  • Utilizes field-proven measurement components
  • Unique optics minimize alignment sensitivity
  • Utilizes proven and patented non-contacting, air-bearing technique for passline stabilization
  • Purged measurement cavity keeps measurement windows clean
  • Precise factory pre-calibration. Permanent, simple check samples included
  • Compact, modular head design with top, bottom or twosided measurements possible
  • Field-proven for interface to calender and supercalender controls
  • Supported by ABB’s worldwide network of service professionals
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