No. 48 - Film/Sheet Thickness Sensors

Film gauge control was of limited effectiveness before there was a means of online thickness measurement. The first non-contact beta-type nuclear gauge was created in 1948 by Tracerlab, now part of EGS Gauging. Beta, gamma-backscatter, infrared, and laser thickness gauges didn’t appear in commercial use until the late 1960s.

NDC Systems (now NDC Infrared Engineering) pioneered gamma-backscatter thickness sensing in 1967. Landis & Gyr (which became Betacontrol GmbH) offered its first beta gauge in 1970. NDC got into beta gauges in ’93 with the first low-energy source of beta radiation on the market (200 millicuries of radiation vs. 1200 for most beta gauges).

At NPE ’71 Industrial Nucleonics in Columbus, Ohio, demonstrated its Accu-Ray 800 beta gauge to control film thickness using a “minicomputer” to monitor and record production data. (Industrial Nucleonics later became Accu-Ray and ultimately part of ABB Industrial Systems.) At the same NPE, Brun Sensor Systems, also in Columbus, demonstrated an IR thickness sensor to control blown film.

Winzen International in Minneapolis built the first capacitive thickness sensor for blown PE film, which Winzen welded together to make stratospheric weather balloons for the U.S. military. Kundig in Switzerland built a circular oscillating mounting for the sensor. But the Winzen sensors were so large and heavy that Kundig started building its own lighter sensors in 1984.

Individual layer thickness sensing for coex films was developed by Topwave Oy (now part of Davinor) in Finland in 1978. At NPE ’85, Fife Corp. introduced an IR sensor able to detect tie layers.