A Microwave Reflection-Based Measurement System for Moisture Detection in Textiles

In industrial laundry facilities it is important to ensure that the clothing is sufficiently dried after the cleaning process to minimize the risk of foxing of the textiles but in contrast the textiles should not be dried too aggressively since this would cause wear in the textiles and unnecessarily increase the power consumption of the drying process. Therefore, precise monitoring of the drying process to identify and optimize the relevant parameters is a great chance to reduce cost and increase the quality of service. In this paper a microwave reflection-based measurement solution, as well as the data processing and calibration algorithm will be described to estimate the remaining moisture in moving textiles. For this a low-cost network analyzer is connected via a multiplexer to multiple antennas, whose reflection parameters are measured over a frequency range of 2.4-2.5 GHz. Since the emitted wave is reflected not only by the textile under test, but also by the environment, additional signal processing is necessary to minimize measurement errors. A calibration procedure is implemented, which uses three on-site measurements to maximize the signal of interest. With additional calculations the system is then able to estimate the remaining moisture content in the textile. In laboratory experiment this procedure was tested and verified.