Reversible Storage-Induced Bias in Polymer Capacitive Relative Humidity Sensors

Capacitive polymer relative humidity (RH) sensors are widely used in environmental monitoring systems; however, sensors stored for extended periods prior to deployment may exhibit systematic measurement bias that is often misinterpreted as calibration drift. These sensors operate by measuring changes in the dielectric properties of hygroscopic polymer films as water vapor is absorbed into the sensing layer [1,4]. Although these sensors typically demonstrate stable performance following calibration, devices stored for extended periods prior to deployment may exhibit systematic RH offset when placed into service.