Over the past ten years a noncontact resistance monitor has been developed for measuring the deposit above each evaporator on resistanceheated 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.
Sensor Review – Emerald Publishing
Published: Apr 1, 1992