A novel NIR laser-based sensor for measuring the surface moisture in polymers

摘要: Abstract In addition to bulk moisture, the measurement of moisture profiles is very important in pharmacy, food, construction and car industries, military, etc. special cases, upper layers, close surface at surface, affects various processes more intensively. Existing measuring principles, such as those based on nuclear magnetic resonance, are unsuitable for particular applications. For this reason, a novel, non-contact, light-reflection type sensor was designed investigated (patent pending). It water molecule's light-absorbing characteristics near-infrared (NIR) spectrum. order be able measure near-surface complex geometry with thin walls, light from double laser diode led through an optical fiber reflected back InGaAs photodiode detector. The high stability relatively low-cost source achieved constant-power laser-control circuit. sensor's response measured by precision embedded data acquisition system NI CompactRIO evaluated using analyzer, which measures loss-on-drying technique. results prove that it possible polymer layers approximately 0.1% effective resolution content below 2 %.