OPTICAL SENSORS MONITOR METALLIZED FILM PRODUCTION

Over the past ten years a non‐contact resistance monitor has been developed for measuring the deposit above each evaporator on resistance‐heated evaporative metallizers. This is the eddy current type. The flux from an RF coil links with the metallized film. The resultant induced current in the film, which is proportional to the thickness of the deposit, is measured (see Figure 1). Normally, sensor coils are positioned in line with evaporators. The RF sensor head is located next to an insulated roller carrying the metallized film.