Vibrational Frequency
Molecular excitation at higher energy levels produces harmonic signals at multiples of the fundamental vibrational frequency. Detection of overtone vibration allows near-infrared sensors to identify the moisture content of raw wool or cotton bales.
Spectral Fingerprint
Analysis of these secondary signals provides a clear view of the chemical composition of a fabric blend. Although an overtone vibration is weaker than its fundamental counterpart, it falls within the sensitive range of silicon and InGaAs detectors. Sorting machines use these specific peaks to separate polyester from cotton with high precision.
Measurement Calibration
Mathematical models transform the complex overlapping peaks into a readable composition percentage for the user. Because an overtone vibration can be influenced by the physical structure of the knit or weave, the software must account for light path variations. Calibration sets built from thousands of known samples ensure the accuracy of the final classification.
Commercial Value
Moisture level verification prevents the purchase of excess weight in raw fibre transactions. Identifying the overtone vibration associated with water allows buyers to pay only for the dry weight of the material plus the standard regain. This checkpoint protects the profit margins of spinning mills and garment manufacturers alike.
