This chapter discusses the design of resonator sensors for two applications of interest. One is a wide latex-coated fabric moving on a production line with the sensors monitoring the coating thickness or, alternatively, the moisture content in the fabric for the purpose of controlling the amount of latex on the fabric. The second is a rubber sheet moving on a calender (a cylindrical drum) in which the interest is the thickness of the sheet. Selection of physical parameters, dimensions and operational parameters, and the simulations necessary are discussed. Alternative designs including multiple sensors and moving sensors for full coverage of the fabric are weighed, and an appropriate design is reached. The details of design are given in full with alternatives and justification so that the reader has full accounting of what the design involves and what to expect from the final product. The most common alternative measurement methods of low-density dielectrics such as fabrics, paper, and thin rubber are either nuclear (by measuring absorption of gamma or beta particles from a radioactive source) or through transmission and/ or reflection of electromagnetic waves. In some cases, the methods are more primitive than that; a sample of the final product is cut and weighed to ascertain that the coating is within the required limits. Because this must be done after the production process, it is extremely wasteful and whole production runs may need to be scrapped due to insufficient or overcoating. The purpose of the designs described here is to eliminate this uncertainty and monitor the production in real time to offer feedback for continuous correction of the coating thickness.

Chapter Contents:

• 5.1 Introduction
• 5.2 Sensor design for fabric coatings
• 5.2.1 Sensor modifications and optimization
• 5.2.1.1 The simulation regime
• 5.2.2 Shielding of the sensor
• 5.2.3 Simulation and optimization
• 5.2.4 Sensitivity to motion of the plates
• 5.2.5 Mechanical design
• 5.3 Sensor design for rubber thickness sensing
• 5.3.1 Simulation and optimization
• 5.4 Alternative sensing strategies
• 5.4.1 Capacitive sensors
• 5.4.2 Reflection and transmission sensors
• Further reading

Inspec keywords: rubber; coatings; resonators; fabrics; dielectric measurement; sensor fusion; thickness measurement; moisture measurement

Other keywords: coating thickness monitoring; resonator sensor design; multiple sensor; cylindrical drum; electromagnetic wave reflection; latex-coated fabric monitoring; production line; low-density dielectric measurement; rubber thickness monitoring; rubber sheet; radioactive source

Subjects: Waveguide and microwave transmission line components; Sensing devices and transducers; Measurement of basic electric and magnetic variables; Dielectric variables measurement; Hygrometry; Corrosion, oxidation, etching, and other surface treatments; Spatial variables measurement; Humidity measurement; Spatial variables measurement; Sensing and detecting devices