What Sensor Calibration Is and Why Readings Drift
Calibration maps sensor error against traceable standards, while drift stems from physical aging, mechanical strain, and environmental stress over time.
Polymer Moisture Creep
Material Deformation
Humidity levels in the environment affect the physical dimensions and mechanical properties of synthetic resins and plastics. Polymer moisture creep describes the slow, time-dependent strain that occurs when a plastic component is subjected to a constant load in a humid environment.
Structural Change
Water molecules penetrate the polymer chains and act as a plasticizer, which reduces the internal friction between the molecular structures. As a result, polymer moisture creep allows the material to deform more easily under stress than it would in dry conditions. This behavior is a significant concern for the housings of precision sensors, where a change in shape could misalign optical paths or stress delicate electronic connections.
Long Term Loading
Designers must account for the combined effects of temperature and humidity when calculating the structural integrity of a device. Failure to model polymer moisture creep can lead to the loosening of fasteners or the cracking of seals after several years of service.
Reliability Testing
Accelerated life tests in environmental chambers help predict the extent of this deformation over the intended lifespan of the product. Controlling polymer moisture creep ensures that mechanical tolerances remain within acceptable limits for the duration of the equipment’s use.