Characterization of Capacitive Sensors for In-Flow Cotton Moisture Sensing
Sushma Perati, S.D. Filip To, Sean Donohoe, Xin Zhang, Xinyuan Chen · 2024
Abstract. Two types of capacitive sensors for real-time measurement of cotton moisture content (MC) were evaluated under static condition (velocity = 0) to study their repeatability characteristics, and suitability of use in cotton. The range of MC evaluated was from 3.73% to 21.64% wet basis, and the study found that the sensors had correlation values of 77-88% against measurements by an M5-Thermo 163M moisture balance instrument from Veritas company. An insulated and instrumented conditioning chamber was used to condition the cotton prior to testing. The conditioning chamber included a humidifier, a heat source, and a circulating fan. The control of humidity and temperature inside the chamber was done using commercial temperature, and humidity controllers. Six different relative humidity levels at 50 degrees C were used to produce conditioned cotton with various ranges of moisture content levels. The two capacitive moisture sensors under study were the FP-32C from AgriChem, and a customed plate capacitor sensor. The sensors were mounted in a custom designed instrumented apparatus (Test fixture) that enabled measurements under same volume and contact pressure. With proper fittings and sampling mechanisms, the sensors are suitable for use in real-time in cotton gin environments to close the loop of maintaining ideal moisture content of the cotton being ginned.