Photometric Sensor
Optical sensor technology measures surface absorption of specific infrared light wavelengths to quantify water content in moving paper webs. Non-contact analytical equipment employing near infrared moisture measurement provides continuous moisture monitoring across paper machine drying sections. Filter wheels or solid-state emitters project light at specific water absorption bands alongside reference wavelengths that do not absorb water.
Reflected or transmitted light intensity ratios calculate absolute moisture percentage in real time without physically contacting paper stock. Web moisture data feeds directly into automated machine speed and dryer steam controls to maintain uniform reel moisture. The measurement system applies to continuous web manufacturing and converting lines, terminating application on dry static sheet stacks where optical depth penetration is restricted.
Absorption Physics
Water molecules absorb infrared radiation intensely at specific spectral bands, notably near one thousand four hundred fifty and one thousand nine hundred forty nanometers. Ratio comparisons between absorption wavelengths and non-absorbing reference wavelengths eliminate interference from sheet surface roughness or basis weight fluctuations.
Process Control
Closed-loop machine control systems adjust steam valve positions on dryer cylinders based on continuous moisture sensor signals. Rapid sensor response detects cross-machine moisture streaks, allowing automated profile dampeners to rebalance moisture distribution before reel winding. Maintaining moisture within tight target limits prevents paperboard curl and web breaks during subsequent converting operations.
Target moisture accuracy within zero point two percent ensures consistent dimensional stability across production batches.
