A new optical fiber dew point humidity sensor based on the virtual instrument

Area of Science:

• Materials Science
• Environmental Monitoring
• Optical Sensing

Background:

• Accurate measurement of air dew-point (DP) and relative humidity (RH) is crucial for various environmental and industrial applications.
• Traditional methods for DP measurement can be complex and time-consuming.
• Development of automated, stable, and accurate sensing systems is an ongoing research area.

Purpose of the Study:

• To present a new, automatic method for measuring air dew-point (DP) and relative humidity (RH).
• To demonstrate the functionality and performance of an optical fiber dew-point sensor.
• To validate the sensor's accuracy, stability, and repeatability.

Main Methods:

• Fabrication of a lithium chloride-polyvinyl alcohol sensing film on an optic fiber head.
• Utilizing an optical system to detect changes in the film's refractive index upon dew or frost formation.
• Assembly of an automated measurement system with a dew point sensor head and data acquisition interface.
• Development of LabVIEW 8.6 programs for sensor characterization (response-recovery, temperature, humidity calculation).

Main Results:

• The developed sensor system provides automated measurement of DP and RH.
• The sensor exhibits anti-interference properties and good stability.
• Operational range: 0-30 °C DP and 11-83% RH.
• Repeatability achieved with a standard deviation of 0.09 °C.
• Accuracy demonstrated as < ±0.3 °C for DP and < ±1% RH.

Conclusions:

• The novel optical fiber sensor offers an accurate and reliable method for automated dew-point and relative humidity measurement.
• The system's stability, repeatability, and anti-interference capabilities make it suitable for diverse applications.
• The sensor achieves high accuracy comparable to reference values across its operating range.